BIOLOGY FORM ONE NOTES

Chapter One: Introduction to Biology

Introduction

There are various forms of life on earth ranging from microscopic to macroscopic living things. Such forms of life or living things are studied in Biology. In this chapter, you will learn about the basic concepts and terminologies of Biology, branches of Biology, importance of studying Biology, and the relationship between Biology and other scientific fields. The competencies developed will enable you to use biological principles and processes in everyday life.

Think

Life without Biology

Basic concepts and terminologies in Biology

Task 1.1

Search from library and reliable internet sources information on the basic concepts and terminologies of Biology.

The term 'Biology' originates from two Greek words, bios that means 'life' and logos that means 'study'. Therefore, Biology is a branch of science that deals with the study of life. A person who studies Biology is called a Biologist.

Living things are also called organisms. They include, plants, animals, fungi, and micro-organisms. Micro-organisms are very small living things, such as bacteria and some protozoans, which cannot be seen with the naked eyes. The size of organisms varies and ranges from very small such as bacteria to very large such as trees, birds, hippopotamus, and whales, as shown in Figure 1.1.

[Figure 1.1: Living things (a) tree (b) bird (c) hippopotamus (d) whale]

Figure 1.1: Living things (a) tree (b) bird (c) hippopotamus (d) whale

Life

Life is a state that distinguishes living things from non-living things. It is characterised by nutrition, respiration, excretion, growth and development, sensitivity or irritability, movement, and reproduction. The basic unit of life is the cell. All living things are made up of cells. Cells are so small that they cannot be seen with naked eyes. They can only be seen by using the microscope. The microscope is an instrument that is used in scientific studies to enlarge very small things so that they can be easily seen and examined. The process of enlarging very small things is called magnification.

The branches of Biology include Botany, Zoology and Microbiology. Botany is the study of plants, zoology is the study of animals, and microbiology is the study of microbes. A person who is specialised in the study of plants is called a Botanist, a person who deals with the study of animals is called a Zoologist, whereas a person who deals with the study of microbes is called a Microbiologist. However, there are many sub-branches of Biology that deal with different aspects of living things. Examples are given in Table 1.1.

Table 1.1: Other branches of Biology

Branch	Area of study
Anatomy	Body structures of organisms
Cytology	Structure and functions of cells
Ecology	Relationship between organisms and their environment
Entomology	Insects
Genetics	Heredity and variation
Immunology	Immune systems
Mycology	Fungi
Parasitology	Parasites
Taxonomy	Classification of organisms
Physiology	Physical and chemical processes taking place within living organisms

Exercise

1. Explain the term Biology.
2. Differentiate Botany from Zoology.
3. Biology is more than a study of animals and plants. Explain.

Importance of studying Biology

Task 1.2

Search from the library and reliable internet sources information on the importance of studying Biology, then write short notes.

The knowledge obtained from studying Biology is important because it:

1. Helps to understand and care for the environment properly. It helps to learn about the plants, animals, and micro-organisms that surround us and how they affect us.
2. Helps to identify and group living things which makes it easier to learn more about them.
3. Helps to appreciate nature and many fascinating things about different organisms and how their functions are learnt in Biology.
4. Helps to understand our bodies.
5. Helps to acquire research skills that are useful when carrying out scientific investigations. Such skills include measuring, observing, analysing, and drawing conclusion.
6. Helps to improve food production. Scientists can use biological skills to develop higher-yielding and disease-resistant varieties of plants and animals. These improved breeds of plants and animals are called hybrids.
7. Helps to improve the standard of living in human, and care for animals and plants. Skills from Biology can help to determine the causes, symptoms, and methods of transmission of infections and diseases.
8. Helps to answer important questions, such as when and where life originate, how plants move, and how animals survive without plants.
9. Enables scientists to come up with ways to prevent, treat, and cure diseases. This has greatly improved the quality of people's lives. For instance, the first cure discovered for malaria was quinine. It was extracted from the bark of the Cinchona tree (or quinine tree). Quinine has helped to reduce the number of deaths from malaria, especially in Africa.
10. Lays foundation for specialising in careers, such as teaching, nursing, medicine, horticulture, and environmental science.
11. Encourages international cooperation through biological research. For instance, biologists from all over the world cooperate to find cure for diseases, such as COVID-19, AIDS, and Ebola.

Relationship between Biology and other scientific fields

Task 1.3

Search for information from the library and reliable internet sources the relationship between Biology and other scientific fields, then write short notes.

Biology is not an isolated field of study. Biology is related to many other fields of study, such as Agriculture, Medicine, Pharmacy, Veterinary Medicine, and Nutrition. Biological researches have a direct impact on the development of these fields.

Activity: Investigating the relationship between Biology and other fields of science

Materials: Newspapers and magazines with articles on Biology, Agriculture, Medicine, Forestry, and other scientific fields, ICT tools, notebook, and pen

Procedure

1. Collect newspapers and magazines with articles on Biology, Agriculture, Medicine, Forestry, Nutrition, and other fields of science.
2. Search from the library or internet sources the articles on Biology, Agriculture, Medicine, Forestry, Nutrition, and other scientific fields.
3. Go through the articles and state which other fields of study, apart from Biology, are mentioned.
4. Relate Biology to other fields of science, such as Agriculture, Medicine, Forestry, and Nutrition.

Question

Explain the fields that you think are related to Biology. Give examples to explain these relationships.

Agriculture

Agriculture is the field of study which deals with growing crops and rearing animals for food, money, or both. Biological research findings on crops and livestock have led to improved agricultural production. Scientists have developed breeds of crops and animals that mature quickly and produce high yields. For instance, indigenous breeds of chicken start laying eggs when they are about eight months old while the improved breeds known as layers can start laying eggs as early as five months.

Medicine and pharmacy

Medicine is the study of the prevention, treatment, and cure of diseases. Pharmacy is the science of preparation and administration of drugs. Anatomy and Immunology form an important part of the study of medicine.

The study of Anatomy helps medical doctors to learn the structure of the body and how it functions. This makes it possible for them to know what is wrong in the body and how it can be treated. In Immunology, scientists study the body's response to disease-causing agents. This knowledge is important in the formulation of vaccines and drugs that are able to prevent and treat diseases, respectively. Some of these drugs and vaccines are made from animals, plants, fungi, or micro-organisms.

Nutrition

The study of Biology is important in understanding the composition and value of different groups of foods. This knowledge is used by dieticians to determine the kind of diets that are suitable for people with different health needs.

Biologists have also developed breeds of livestock and crops that yield products of higher nutritional value. Examples include varieties of sweet potatoes that are rich in vitamin A and a breed of Jersey cattle which produce milk with low butterfat content. Such breeds are known as improved breeds.

Forestry

Forestry deals with creating, managing, and conserving forests. Forests are sources of fuel (firewood and charcoal), building materials, and medicinal plants. They also serve as water catchments. Biologists have developed varieties of trees that grow well in dry areas. Such trees are used to reclaim dry land for human settlement. Through Biological research, varieties of fast-growing trees have been developed. The fast-growing trees are planted in deforested areas. This is called reforestation. Reforestation helps to preserve water catchments so as to ensure a continuous supply of water. Forests also prevent desertification.

Chapter Summary

1. Biology is the study of living things. People who study Biology are called Biologists.
2. The main branches of Biology include Botany, Zoology, and Microbiology.
3. The cell is the basic functional unit of life.
4. The study of Biology is important because:
   1. It helps us to gain knowledge about our environment and how to improve it.
   2. It is a foundation for specialising in careers, such as nursing, medicine, and teaching.
   3. It helps us to acquire research skills, such as measuring, observing, analysis, and conclusion making skills.
   4. It enables researchers to produce improved breeds of crops and animals.
   5. It enables scientists to come up with the ways of preventing and treating diseases.
   6. It encourages international cooperation in biological researches.
5. Biology is related to other fields of study, such as Agriculture, Medicine, Pharmacy, Veterinary Science, Nutrition, and Forestry.

Revision Exercise 1

Choose the most correct answer.

1. Which of the following fields of study is NOT related to Biology?
   1. Agriculture
   2. Astrology
   3. Medicine
   4. Nutrition
2. Which of the following is a reason for studying Biology?
   1. Biology helps us to appreciate and improve nature.
   2. Biology deals with non-living objects in our environment.
   3. Biology enables us to pollute the environment.
   4. Biological research contributes to the development of low-yielding breeds of crops.
3. The branch of Biology that deals with microbes is called:
   1. Zoology
   2. Microbiology
   3. Botany
   4. Cytology
4. Which of the following is one of the main branches of Biology?
   1. Sociology
   2. Agriculture
   3. Anthropology
   4. Botany
5. Outline four reasons as to why it is important to study Biology.
6. Identify the field and branch of Biology that you will use to solve the following problems:
   1. Helping a person with a broken leg.
   2. Protecting cattle from testse flies.
   3. Conserving village river from drying.
7. Differentiate:
   1. Unicellular from multicellular organisms
   2. Cytology from taxonomy

Chapter Two: Scientific Processes in Biology

Introduction

Science is studied through a procedure that follows systematic processes, which require the use of a variety of apparati and equipment. Among the processes that are conducted to carry out scientific studies include observation, measurement, and experimentation. In this chapter, you will learn about different biological apparati and equipment, and the use of sense organs to make correct observation. You will also learn how to measure mass, length, and temperature. Likewise, you will learn the steps for carrying out scientific studies, commonly known as the scientific methods. The competencies developed will enable you to apply scientific methods, appropriately use biological apparati, make accurate observations using sense organs, and perform accurate measurements in various daily life situations.

Think

Studying Biology without conducting experiments

Common Biology Laboratory Apparati, Equipment and Other Resources

Task 2.1

Search from reliable internet sources the video or images showing biology apparati and equipment and their uses. Note down what you have observed.

Biology laboratory is a special room or building designed for carrying out biological experiments. A laboratory should have good qualities and facilities which include large door which open outwards, adequate space for carrying out experiments, proper lighting, good ventilation, a source of water, a source of heating, and adequate space for storing apparati, chemicals, models, and specimens.

A wide variety of apparati (singular is apparatus) and equipment are needed in order to conduct Biology practical. The following are some common Biology laboratory apparati, equipment and resources:

Hand Lens

This is mainly used to magnify specimens that are under observation. A hand lens enables a scientist to magnify small organisms or their parts in order to observe them clearly.

Sweep Nets

A sweep net is used for catching small flying organisms, such as butterflies, grasshoppers and other small animals.

Scoop Nets

These are used for catching fish and other aquatic animals.

Pooter

This is a device that scientists use to pick up small organisms, such as insects without hurting them. The pooter has two tubes. The scientist sucks through one tube and the organism is drawn into the pooter through the other tube.

Quadrat

A quadrat is a wooden square or metallic grid which is used to estimate the number of organisms in an area.

Specimen Bottle

A specimen bottle is a glass or plastic container in which specimens are kept for storage.

Dissecting Kit

A dissecting kit contains tools for dissection of specimens. Some of the items included in the dissecting kit are:

• Forceps for holding specimens
• A pair of scissors for cutting specimens or objects
• Scalpels for cutting
• A needle for loosening internal parts
• Pins for holding specimens in place
• Hand lens for magnifying small specimens or their parts

Thermometer

A thermometer is an instrument used to measure temperature.

Heat Sources

Heat sources are used for heating various things in the laboratory. Examples of heat sources in the laboratory are Bunsen burner, kerosene stove, and spirit burner.

Mounting Needle

A mounting needle is used to lift small delicate specimens.

Microscope Slide and Coverslip

The microscope slide is a small flat piece of glass that is used to hold specimen under observation. A specimen to be observed under a microscope is placed on a slide with a drop of a liquid and covered with a coverslip.

Microscope

A microscope is an instrument that is used during scientific studies to magnify very small specimens so that their details can be seen. The smallest structures of cells, tissues, and organs of organisms can be studied well if magnified by the microscope. There are two types of microscopes: Electron microscope and Light microscope.

The Electron Microscope

The electron microscope uses beams of electrons to magnify specimens. The maximum useful magnification of most electron microscopes is about a million times (1,000,000x). These microscopes are very expensive. They are mostly found in research centres or research institutions.

The Light Microscope

The light microscope is the type of microscope that depends on light to illuminate and magnify tiny specimens. For this matter, it differs from the electron microscope by having lower magnification. The maximum useful magnification of most light microscopes is about one thousand times (1,000x). This type of microscope is commonly used in schools and health facilities.

[Figure 2.12: Parts of the light microscope]

Figure 2.12: Parts of the light microscope

Table 2.1: Parts of the light microscope and their functions

Part	Function
Eyepiece	Has a lens that magnifies the specimen five times (5×), ten times (10×), or fifteen times (15×)
Body tube	Supports the eyepiece and the rotating nosepiece
Rotating nosepiece	Supports the objective lenses. Rotates to allow changes from one lens to another
Objective lenses	Magnify the object under observation. Light microscope usually has three objective lenses: low power, medium power, and high power. A high-power lens reveals more details of the specimen
Coarse adjustment knob	Rises or lowers the body tube in order to bring the image into focus
Fine adjustment knob	Rises or lowers body tube in order to bring the image into sharp focus
Arm	Supports the body tube, knobs, stage, diaphragm and mirror. It is one of the parts that is held when moving the microscope
Stage	Surface on which the specimen is placed
Stage clip	Holds the slide containing the specimen in place
Mirror	Reflects and directs light to the specimen under observation
Condenser	Concentrates light onto the specimen that is placed on the stage
Diaphragm	Regulates the amount of light passing from the mirror to the condenser
Base	Provides firm support for the microscope

How to use the light microscope

1. Place the microscope on the laboratory bench or table. Make sure it is not too close to the edge. Position the microscope such that the arm faces you and the stage faces away from you.
2. Mount the specimen on the microscope slide. Cover it with a coverslip.
3. Make sure that the low objective lens is in line with the eyepiece lens.
4. Place the slide with the specimen on the stage. Hold it in place with the stage clip.
5. While looking through the eyepiece, use your hand to adjust the mirror so that the light is directed to the specimen on the stage. Always keep both eyes open when looking through the eyepiece.
6. Adjust the coarse adjustment knob to bring the specimen into focus.
7. Adjust the fine adjustment knob to bring the specimen into a sharp focus.

Total magnification = eyepiece magnification × objective lens magnification

For example, if the eyepiece magnification is 5× and the objective lens magnification is 40×, then the total magnification is 5 × 40 = 200×

8. Rotate the nosepiece to a higher power objective lens, if you want to observe more details of the specimen.

How to care for the light microscope

• Turn the adjustment knob slowly. Always start with the coarse adjustment knob.
• Lift the microscope using both hands, one hand holding the arm and the other holding the base.
• When not in use, cover the microscope with clean cloth and store it in a dry, dust-free place.
• Clean dirty lenses using lens tissue or a soft cloth.
• Do not place the microscope at the edge of the table or bench as it could be knocked over.
• When the microscope is not in use for a long time, remove the lenses and put them in a desiccator.
• Do not touch the microscope with wet hands.
• Do not touch the surface of the mirror or the lenses with your fingers.
• Lubricate the moving parts regularly.
• Always use the coverslip in order to protect the lenses of the microscope from getting into contact with the specimen.
• Remove the slides from the stage immediately after use.
• Move the objective lenses up when storing the microscope.
• When storing the microscope, rotate the rotating nosepiece so that the low magnification lens is in line with the eyepiece lens.

Activity 2.1: Using the light microscope

Materials: Light microscope, microscope slide and coverslip, razor blade, knife or scalpel, onion bulb, forceps, mounting needle or glass rod, iodine solution, and blotting paper

Procedure

1. Use the knife to cut the onion bulb vertically or lengthwise into four pieces.
Safety precaution: Take precautions when using sharp objects, such as knife and razor blade.
2. Obtain a fresh leaf from one of the quarters.
3. Use a pair of forceps to peel a thin layer from a leaf.
4. Trim the thin layer to approximately 5 mm x 5 mm using the scalpel or knife.
5. Put a drop of water on the microscope slide. Place the trimmed thin layer of onion leaf in the drop of water using a glass rod or a mounting needle.
6. Gently cover the specimen with a coverslip making sure that no air bubbles are trapped inside.
7. Dry any excess water from the sides of the coverslip using a blotting paper.
8. Mount the slide on the stage of the light microscope. Hold it in place with the stage clips.
9. Observe the specimen under the low power objective lens, then observe under the medium power objective lens.
10. Remove the specimen from the microscope stage. Remove the specimen from the slide and put a new specimen. Put a drop of iodine on the specimen. Repeat the procedures. Iodine makes the specimen clear. Use blotting paper to eliminate any excess iodine.
11. Observe the specimen again under low power and medium power objective lenses.
12. What did you observe?

Basic Skills in Scientific Studies

Task 2.2

Search from library and reliable internet sources the information on basic skills in scientific studies. Write short notes.

There are basic skills that are essential in scientific studies. The skills are needed in studying Biology. They include observation, measurement, and experimentation.

Observation

Observation is one of the methods of studying Biology. Through observation one can study living things in many ways. Observation is done by using sense organs.

We have five sense organs. These are eyes, ears, skin, nose, and tongue. The observation process with the help of sense organs enables you to study living organisms. For instance, if you have a coconut, you can use your sense organs to determine that:

• It is round by seeing.
• It contains a liquid by hearing the sound when shaken,
• It has a rough husk by touching,
• It has a good smell by smelling (after breaking the coconut), and
• It has a sweet taste by tasting (after breaking the coconut).

Activity 2.2: Making observations using sense organs

Materials: Colourful pictures, insects, preserved specimens, flowers, perfume, whistle, bell, stones, wooden objects, pieces of cloth, ice, hot water, and lukewarm water

Procedure

1. Carefully observe the specimens provided using your sense organs.
Safety precautions: Do not taste anything in the laboratory. They may be contaminated with poisonous materials or they may be poisonous themselves.
2. Note down the features of each specimen you have observed.
3. Draw a table similar to Table 2.2 in your exercise book. Record the observations by putting a tick (√) on each object.

Table 2.2: Observation of objects using sense organs

Object	Sight	Hearing	Smell	Touch
1. Flower
2. Perfume
3. Whistle
4. Cloth

Measurements

Scientists use specific instruments and units of measurement in their investigations. The standard system of measurement used by scientists all over the world is called the International System of Units (SI units). This system ensures precision in the presentation of scientific results and the uniformity of data presentation internationally. It also enables scientists to confirm results from other parts of the world. Table 2.3 shows some common measurements in Biology and their units.

Table 2.3: Fundamental quantities

Measurement	SI unit	Symbol	Other common units
Mass	Kilogram	kg	Grams (g)
Length	Metre	m	Millimetre (mm), Centimetre (cm) Kilometre (km)
Temperature	kelvin	K	Degrees Celsius (°C), Degrees Fahrenheit (°F)
Time	Second	s	Minutes (min), Hour (hr)

Mass

Mass is the quantity of matter of an object. Everything in the world is made up of matter. Mass is measured using a weighing balance or a weighing scale. It is often expressed in grams (g) or kilograms (kg), whereby 1000 g = 1 kg. The weighing balance can be manual or digital.

Length

Length is a measurement of the distance or dimension from one point to another. For example, you can measure the height of a human being, and plant, as well as the length of a leaf and fish.

Length can be measured using a ruler or tape measure. Common units of expressing length are millimetres (mm), centimetres (cm), metres (m), and kilometres (km). These units of length can be converted into other units, as shown in Table 2.4.

Table 2.4: Conversion of some measurements

10 mm = 1 cm	1000 m = 1 km
100 cm = 1 m	100,000 cm = 1 km

Temperature

Temperature is the degree of hotness or coldness of a substance. It is a physical property that explains the common notions of hot and cold. The common units for measuring temperature are kelvin (K), degrees Celsius (°C), and degrees Fahrenheit (°F). These units relate as follows:

K = °C + 273.15

F = [(9/5) × °C] + 32

°C = 5/9 (F - 32)

The normal human body temperature is between 36 °C and 37 °C.

Thermometer is used to measure temperature. It can measure human body temperature and temperature of liquids, such as water. The boiling point of water is 100 °C and its freezing point is 0 °C.

Scientific Methods

Task 2.3

Search from library and reliable internet sources the information on scientific methods.

Science is the knowledge and systematic study of the structure and behaviour of the natural and physical world. It is based on facts that can be proven through observation and experiments. In order to study situations and come up with solutions to the problems, scientists follow a set of steps called the scientific method. The scientific method is a way of studying things by testing facts systematically. It follows seven steps which are: identifying the problem, formulating a hypothesis, experimentation, observation and recording data, data analysis and interpretation, conclusion, and reporting results.

Identifying the problem

This is where a scientist makes a puzzling observation. The observation can be made in the environment or from the work of other scientists. An example of such an observation is: 'Earthworms are mostly found in cool and well-shaded soil'. After making an observation, the scientist asks questions that can be answered by gathering evidence. For example: 'What conditions make earthworms prefer cool shaded areas to open well-lit areas?'

Formulating a hypothesis

A hypothesis (plural is hypotheses) is a suggestion of the answer to the question asked. It is an intelligent guess that tries to explain an observation. For example: 'Earthworms prefer cool well-shaded areas because these areas have higher moisture than open well-lit areas.'

Experimentation

An experiment is a scientific procedure carried out under controlled conditions to determine whether a hypothesis is correct or not. In an experiment, a scientist uses variables to test a hypothesis. Variables are conditions or factors that can change or can be changed. Examples of variables include temperature, speed, and light. They can be classified as dependent, independent, and controlled variables.

Dependent variable: This is the condition or factor that is measured or tested to obtain the results of the experiment.

Independent or manipulated variable: This is a condition or a factor that the researcher changes systematically to obtain different results.

Controlled variable: This is the condition or factor that is kept constant during the experiment.

Observation and data recording

The scientist observes what happens from the time the experiment is set up to the time it ends. It is important to note all the changes made in the independent variable and the resulting changes in the dependent variable.

Data analysis and interpretation

At the end of the experiment, the scientist analyses the observations and data recorded. The scientist may also look for patterns or trends in the data.

Conclusion

A conclusion is a statement that summarizes what a scientist has learnt from an experiment. When scientists reach a conclusion, they state whether the data or information collected supports their hypothesis or not. Conclusions often lead scientists to pose new questions and plan new experiments to answer them.

Reporting results

Scientists communicate their results to others in a final report. They can present the results to the scientific community by publishing their final report in a journal or at seminars, conferences, workshops, and meetings.

Chapter Summary

1. Biological apparati are instruments and equipment needed for effective studying of Biology.
2. Some of the apparati used in studying Biology are hand lens, sweep nets, scoop nets, pooters, specimen bottles, quadrats, dissecting kits, mounting needles, slides, coverslips, and microscopes.
3. A microscope is an instrument that is used during scientific studies to magnify very small specimens so that their details can be seen clearly.
4. There are two types of microscopes: light microscope and electron microscope.
5. The total magnification in a microscope is calculated using the following formula:

   Eyepiece magnification × Objective lens magnification

6. Observation, measuring, and experimentation are skills needed when studying Biology.
7. Sense organs used to make observations are:
   1. Eyes for seeing.
   2. Nose for smelling.
   3. Ears for hearing.
   4. Tongue for tasting.
   5. Skin for feeling.
8. Scientific measurements are taken using specific instruments and are expressed in specific units. Some basic biological measures are:

   Measure	Instrument	SI unit
   Mass	Weighing balance	Kilogram (kg)
   Length	Ruler, tape measure	Metre (m)
   Temperature	Thermometer	kelvin (K)

9. The scientific method is a set of steps that scientists use to study things systematically. It involves:
   1. Identifying the problem.
   2. Formulating a hypothesis.
   3. Experimentation.
   4. Observation and recording data.
   5. Data interpretation.
   6. Conclusion.
   7. Reporting results.
10. Simple biological experiments are performed to study different features of living things.

Revision Exercise 2

1. Identify the apparatus or equipment you can use to perform each of the following biological activities:
   1. Catch a frog from a pond in order to study its external features.
   2. Collect insects and small animals from the school compound.
   3. Estimate the number of small organisms per square metre.
2. As a biology student, how would you help your friend to label and state the functions of the parts of the microscope?
3. Amina was performing an experiment. Some of her specimens were very delicate and small. Which apparatus was she supposed to use in order to lift these specimens from the specimen bottle?
4. John attempted to observe plant cells using a prepared slide under a light microscope, but he was unable to obtain a clear image due to the following challenges:
   1. The slide containing specimen did not settle on the stage for observation.
   2. He was unable to achieve sharp focus.
   3. The image was too bright, making it difficult to see the detail of specimen.
   Educate your friend on how to address the challenges faced in order to obtain a clear image of the plant cells.
5. Biology students were assigned to observe the external features of a variety of preserved specimens.
   1. Mention the sense organ that the students would primarily use, and explain its function.
   2. Give one disadvantage of using sense organs to make observations.
6. Why is it important for scientists to use a standard system of measurement?
7. Name the instrument you would use to measure the following and state their corresponding SI units.
   1. Time
   2. Mass
   3. Temperature
   4. Length
8. 1. Convert the following temperatures into degrees Fahrenheit
      1. 36 °C
      2. 40 °C
   2. Convert the following temperatures into kelvin
      1. 100 °C
      2. 0 °C
   3. Convert the following temperatures into degrees Celsius
      1. 57 K
      2. 273 K
      3. 142 °F
      4. 43 °F
9. Imagine you are a student. Your Biology teacher has tasked you to measure the length and width of a leaf.
   1. What instruments would you use to ensure accurate measurements?
   2. What steps would you follow to obtain reliable data?
10. As a biologist, you have observed that children in your village are getting frequent fever accompanied with vomiting and headaches. This is not observed in a neighbouring village where there is wide use of mosquito nets. You are supposed to address this problem using scientific method. Explain the steps that you would follow to address this problem.

Chapter Three: Cell Structure and Organization

Introduction

All living things are made up of cells. The cell is the basic functional unit of life. In this chapter, you will learn about the meaning of the cell, characteristics of the cell, and the functions of different parts of animal and plant cells. You will also learn the similarities and differences between plant and animal cells. In addition, you will learn the concept of cell differentiation and its importance to the formation of tissues, organs, and organ systems. The competencies developed will enable you to learn better other biological processes.

Think

Life without cells

The Cell

Task 3.1

Search from library and reliable internet sources the information about cell.

In 1665, an English scientist Robert Hooke revolutionized our understanding of life by designing a microscope and examining cork from a tree's bark. He discovered that the cork consisted of numerous box-like structures that are closely packed together, resembling a honeycomb. These structures were named 'cells'. Since then, it has been revealed that living things are made up of one or more cells, which serve as fundamental units of life. All essential life processes occur within the cell.

The remarkable observations and conclusions made by Hooke, along with other scientists, paved the way for the development of the cell theory. This widely accepted theory indicates the relationship between cells and living things.

Components of the Cell Theory

1. All living things are composed of one or more cells.
2. Cells are the basic unit of structure and functions of living things.
3. All cells are produced from other cells.
4. Cells contain inheritable information which controls their activities.
5. All cells are basically similar in chemical composition.
6. All life processes take place in the cells.

The cell theory applies to all living things, no matter how big or small they are. Since cells are common to all living things, they can provide information about life. Scientists can use the concept of cell theory to learn about nutrition, growth, reproduction, respiration, movement, sensitivity, and excretion.

Types of Cells

Task 3.2

Search from reliable internet sources the simulations/videos/images that show prokaryotic and eukaryotic cells. Note down what you have observed.

Activity 3.1: Exploring prokaryotic and eukaryotic cells under the microscope

Materials: Microscope, prepared slides of prokaryotic cells and eukaryotic cells or charts showing prokaryotic cells and eukaryotic cells, notebook, and pencil or pen

Procedure

1. Prepare the microscope with the appropriate magnification power for the slides.
2. Mount the slide of prokaryotic cell on the light microscope's stage. Hold it in place with the stage clips.
3. Observe the structure of the prokaryotic cell under the microscope.
4. Replace the slide with a prepared slide of eukaryotic cell and focus on different areas of the slide. Observe the structure of the eukaryotic cell.
5. Record the observations.
6. Describe your observations.

Question

Based on your observations, explain the similarities and differences between prokaryotic cell and eukaryotic cell.

Prokaryotic Cells

The prokaryotic cell is a type of cell in which the nuclear materials are not bound with a membrane. The cell is found in organisms called prokaryotes. Prokaryotes are single-celled organisms, such as bacteria and blue-green bacteria.

Characteristics of prokaryotic cells:

• They do not have true nucleus, as they lack membrane bound nucleus.
• They do not have membrane-bound organelles, such as mitochondria.
• They reproduce by binary fission and sometimes by conjugation.
• Mostly they are smaller in size than eukaryotic cells.
• Some prokaryotes have whiplike structure called flagella for locomotion or hair-like structure called pili for attachment.
• Have circular Deoxyribonucleic acid (DNA).
• Can be rod-shaped, spherical-shaped, spiral-shaped, or comma-shaped.

[Figure 3.1: Shapes of prokaryotes (a) spiral-shaped (b) spherical-shaped (c) rod-shaped (d) comma-shaped (e) spirochaete-shaped]

Figure 3.1: Shapes of prokaryotes

Eukaryotic Cells

These are types of cells whose organelles are enclosed in a membrane. The cells are found in organisms called eukaryotes.

Characteristics of eukaryotic cells:

• They have a membrane-bound nucleus.
• They are generally larger and more complex than prokaryotic cells.
• They contain specialised membrane-bound organelles, such as mitochondria and chloroplasts.
• They have linear DNA.

Animal and Plant Cells

Both animals and plants are made up of eukaryotic cells. However, these cells differ in their structure and functions.

The Animal Cell

Task 3.3

Search from reliable internet sources the simulations showing animal cells. Note down what you have observed.

An animal cell is a type of eukaryotic cell that lacks cell wall and has true membrane bound nucleus.

[Figure 3.2: A generalised structure of an animal cell]

Figure 3.2: A generalised structure of an animal cell

Activity 3.2: Observing animal cells

Materials: Prepared slides of a cheek cell, a microscope, ICT tools, notebook, and a pen or pencil

Procedure

1. Prepare the microscope with the appropriate magnification power.
2. Mount the prepared slide on the stage of the light microscope.
3. Use the microscope to focus on different areas of the slide.
4. Use a low-power objective lens to observe the prepared slide.
5. Draw what you have observed.
6. Search from the library, internet sources and other biology books the structures of human cheek cells.
7. Compare what you have observed and what you have searched from different sources with Figure 3.3.

[Figure 3.3: Human cheek cells]

Figure 3.3: Human cheek cells

Question

Describe the structure of human cheek cells.

Functions of different parts of an animal cell

Task 3.4

Search information from biology books and reliable internet sources on the parts of an animal cell and their functions.

Cell Membrane

The cell membrane is a thin layer that encloses the whole cell. The cell membrane is made up of two layers of lipids and protein molecules. This membrane is flexible and semi-permeable. Semi-permeable means that it allows certain substances to pass in or out of the cell. Flexibility of animal cell membrane and the lack of cell wall gives it an irregular shape.

Cytoplasm

This is a jelly-like substance made up of water and dissolved chemical substances. The cytoplasm is the site for many chemical reactions in the cell. Cell organelles, such as the vacuoles, nucleus, and mitochondria are suspended in the cytoplasm.

Nucleus

This is a spherical organelle suspended in the cytoplasm. The nucleus consists of nucleolus and a fluid called nucleoplasm. It is surrounded by a membrane called the nuclear membrane.

Functions of the nucleus:

• It determines the chemical processes that take place in the cell.
• It controls the functions of the cell.
• It determines the cell's size, shape, and functions.
• It determines the hereditary characteristics of a cell.

Cell Vacuoles

Cell vacuoles are fluid-filled spaces bound by a membrane. Animal cells have small and temporary vacuoles, mainly used to secrete and excrete wastes from the cell.

Mitochondria

Mitochondria (singular is mitochondrion) are oval-shaped organelles that have two membranes. The outer membrane is smooth. The inner membrane has folds called cristae (singular is crista). The role of mitochondria is to produce energy for the cell. That is why they are sometimes referred to as 'power houses of cells'.

[Figure 3.4: The structure of a mitochondrion]

Figure 3.4: The structure of a mitochondrion

The Plant Cell

Task 3.5

Search from reliable internet sources the simulations/videos that show plant cells. Note down what you have observed.

[Figure 3.5: A generalised structure of a plant cell]

Figure 3.5: A generalised structure of a plant cell

Similar to the animal cell, the plant cell has a cell membrane, cytoplasm, nucleus, and mitochondria. These organelles function in the same way as those of an animal cell. However, plant cells have additional structures which serve specific roles in plants.

The Cell Wall

This is an outer cover made of cellulose that surrounds the cell membrane. The cell wall is fully permeable. It allows the passage of water and minerals. The cell wall protects and supports the cell. The cell wall gives the plant cell a definite shape.

Chloroplasts

Chloroplasts are oval organelles that contain green pigments in plants. This pigment is called chlorophyll. It is important in photosynthesis, the process by which green plants make their own food. Chlorophyll absorbs light energy needed for photosynthesis.

Cell Vacuole

Plant cells have a large and permanent vacuole that usually occupies the central part of the cell. This vacuole contains sap and is surrounded by a membrane called tonoplast. The cell sap causes the cytoplasm to be pushed outwards against the cell wall. This makes the cell firm, hence helps plant cells to maintain their shape.

Activity 3.3: Observing the plant cell

Materials: Onion, knife, forceps, mounting needle, microscope, microscope slide, coverslip, notebook, and a pen or pencil

Procedure

1. Separate a fleshy leaf from an onion bulb.
2. Cut a small square of the leaf.
Safety precaution: Take precaution when using sharp objects such as knife, forceps, and mounting needle.
3. Using forceps, peel off the epidermis from the inner surface of the square.
4. Put it on a microscope slide, and add a drop of water.
5. Using forceps, a mounting needle, or sharp pencil point, carefully lower a coverslip over the epidermis specimen.
6. Use a low-power objective lens to examine the specimen under the microscope.
7. Draw what you see under the microscope. Compare your diagram with Figure 3.6

[Figure 3.6: Structure of onion epidermal cells]

Figure 3.6: Structure of onion epidermal cells

Questions

1. Describe the structure of a plant cell.
2. Based on your observations on Activities 3.2 and 3.3, explain the similarities and differences between plant and animal cells.

Similarities and Differences between Animal and Plant Cells

Similarities

Animal and plant cells are similar in that both have a cell membrane, cytoplasm, a nucleus, cell vacuoles and mitochondria.

Differences

Table 3.1: Differences between plant and animal cells

Plant Cell	Animal Cell
Has a cell wall	Has no cell wall
Has chloroplast	Lacks chloroplast
Has a large and permanent central vacuole	Has small and temporary vacuoles
It is regular in shape	It is irregular in shape
Nucleus is located at the periphery	Nucleus is centrally positioned
Stores food in the form of starch	Stores food in the form of glycogen

Exercise

1. What are the differences between prokaryotic and eukaryotic cells?
2. Mention the structures that are found in plant but not in animal cells.
3. Draw a diagram of an animal cell and label the parts which perform the following functions.
   1. Energy production
   2. Control all the functions of the cell
   3. Suspended organelles
   4. Allow passage of some substances

Cell Differentiation

Task 3.6

Search from the library and reliable internet sources the information about cell differentiation, then write short notes.

An organism that is made up of one cell is called a unicellular organism. Examples of such organisms are Amoeba sp., Paramecium sp., and bacteria. In such organisms, only one cell carries out all the life processes, such as respiration, reproduction, and excretion.

Organisms made up of more than one cell are called multicellular organisms. A multicellular organism consists of a few to millions of cells. These cells have different functions and have features that make them better suited to carry out these functions. This is called cell differentiation. Cell differentiation is the process in which a cell changes from one form to another and becomes more specialised to perform specific functions.

A group of cells that perform the same function form a tissue. Examples of animal tissues are bone, muscle, and blood. Examples of plant tissues are xylem and phloem.

[Figure 3.7: Examples of animal tissues]

Figure 3.7: Examples of animal tissues

An organ consists of different tissues that work together to perform a certain function. Animal organs include the heart, liver, stomach, and brain. Plant organs include the stem, flowers, fruits, leaves, and roots.

An organ system is made up of organs that work together to perform a certain function. Examples of systems are respiratory system, digestive system, reproductive system, hormonal system, skeletal system, and blood circulatory system. For example, the blood circulatory system transports blood to all parts of the body. It consists of the heart, blood vessels, and blood itself.

Most multicellular organisms are made up of different organ systems working together. Therefore, there is special organisation from the cell to tissue, tissue to organ, organ to organ system to organism.

Importance of Cell Differentiation

Cell differentiation leads to division of labour. Division of labour among the cells means specific cells performing specific functions. This helps the body to carry out all life processes at the same time and more efficiently.

Specialized Animal Cells

White Blood Cells

White blood cells are also called leucocytes. They protect the body against illness and diseases. The cells can change their shapes so as to engulf and destroy harmful microorganisms. Some cells contain digestive enzymes which destroy the microorganisms.

[Figure 3.10]

Red Blood Cells

Red blood cells are also called erythrocytes. They lack nuclei and are bi-concave in shape. This provides a large surface area for transportation of oxygen from the lungs to various parts of the body. They also contain haemoglobin which carries oxygen to different parts of the body.

[Figure 3.11]

Sperm Cells

The sperm cell fertilizes the female egg during reproduction. The sperm cell has a head and a tail. The tail enables the sperm cell to swim to the egg.

[Figure 3.12]

Specialized Plant Cells

Root Hair Cells

Root hair cells absorb water and mineral salts. They help to increase the surface area for absorption.

[Figure 3.13]

Guard Cells

Guard cells surround the stomata. They control the opening and closing of stomata (singular is stoma) of the leaf. The inner walls of guard cells are thicker than the outer walls. This makes them expand irregularly. When the guard cells expand, the stoma opens. When they contract, the stoma closes. Stomata are tiny pores used for gaseous exchange and loss of excess water.

[Figure 3.14]

Xylem Vessels

Xylem vessels are made up of hollow dead cells with walls made up of lignin. Lignin is a tough rigid material that makes up the wall of xylem vessels. The cells are connected to form xylem vessels. These vessels transport water and minerals from the root to the leaves. They also provide support to the plant.

[Figure 3.15]

Palisade Cells

Palisade cells found in plant leaves, contain large amounts of chloroplasts. Chloroplasts are the sites for photosynthesis. They contain chlorophyll which traps sunlight energy during photosynthesis.

[Figure 3.16]

Chapter Summary

1. The cell is the basic functional unit of life.
2. There are two main types of cells: prokaryotic and eukaryotic.
3. Animal cells and plant cells are eukaryotic cells.
4. The structures that are found in plant cells but not in animal cells are the cell wall, chloroplasts, and cell sap vacuoles.
5. Cell differentiation refers to the way cells are specialized to perform a specific function.
6. A tissue is a group of cells that perform the same function.
7. An organ is made up of various tissues that work together to perform a specific function.
8. An organ system consists of organs that work together to perform a specific function.
9. Examples of specialized animal cells are white blood cells, red blood cells, and sperm cells.
10. Examples of specialized plant cells are guard cells, root hair cells, and palisade cells.

Revision Exercise 3

1. One of the following is NOT a component of the cell theory:
   1. All living things are composed of cells.
   2. All cells are produced from other cells.
   3. All cells are basically similar in chemical composition.
   4. All life processes take place outside the cells.
2. One of the following is NOT a characteristic of prokaryotic cells.
   1. They have no nuclear membrane.
   2. They reproduce by binary fission.
   3. They have circular DNA.
   4. They have mitochondria.
3. Which of the following is the functional unit of life?
   1. Tissue
   2. Cell
   3. Organ
   4. System
4. Which of the following organism has differentiated cells?
   1. Bacteria
   2. Amoeba
   3. Plants
   4. Paramecium
5. Write TRUE for correct statements and FALSE for incorrect statements in the spaces provided.
   1. A tissue comprises different organs that perform the same function. ______
   2. Chloroplasts and mitochondria perform similar functions. ______
   3. Palisade cell is one of the specialised cells in plants. ______
   4. A cell membrane is similar in function to a cell wall. ______
6. The following terms are arranged in alphabetical order. Rearrange them into an appropriate biological sequence, starting with the lowest level.

   cell → organ → organism → system → tissue

7. Name the parts of the cell described in each of the following statements.
   1. The semi-permeable membrane that encloses the cytoplasm of a cell.
   2. A large cellular organelle that contains hereditary information.
   3. The site for respiration in the cell.
   4. A jelly-like mixture consisting mostly of water, located between the cell membrane and the nucleus.
   5. A part that protects, supports, and gives shape to plant cells.
8. Differentiate:
   1. Prokaryotic from eukaryotic cells
   2. Organ from tissue
9. Compare the structures of a plant and an animal cell as seen under the light microscope.
10. Explain what will happen if the following are removed from the plant or animal cell.
    1. Nucleus
    2. Cell wall
    3. Chloroplast
    4. Mitochondria
11. Using examples of plant and animal cells, explain the meaning of cell differentiation.
12. Describe the functions of any three specialised cells in plants.

Chapter Four: Classification of Living Things

Introduction

There are different kinds of organisms in the world. Some are too small, they cannot be seen with naked eyes. Such organisms are called micro-organisms. Others can be seen with the naked eyes and are called macro-organisms. Due to the existing diversity of organisms, it is difficult to correctly identify and determine the exact position of organisms in classification. In this chapter, you will learn about the concept of classification, classification systems, ranks of classification, and binomial nomenclature. The competencies developed will enable you to identify and classify newly discovered organisms correctly by comparing their characteristics with the already classified organisms.

Think

Living things with no assigned names

Concept of Classification

Task 4.1

From reliable internet sources, library and other biology books, read about the meaning and importance of classification.

The process of grouping organisms according to their similarities and differences is called classification. Similar organisms are placed in the same group. The similarities can be in terms of their evolutionary relationship or the way they carry out life processes, such as feeding and reproduction. The field of biology that deals with classifying organisms is called taxonomy. Organisms, such as snails, orange trees, crocodiles, birds, lions, and baobab trees belong to different groups.

[Figure 4.1: Variety of living things (a) snail (b) orange tree (c) crocodile (d) birds (e) lion (f) baobab tree]

Figure 4.1: Variety of living things

Activity 4.1: Grouping living things according to their similarities and differences

Materials: A variety of small plants, insects, and other animals, notebook, and a pen or pencil

Procedure

1. Walk around the school compound and collect a variety of plants, insects, and other small animals.
2. Observe and group the collected organisms according to their similarities and differences.
3. Write the similarities and differences among the grouped organisms.

Caution:

1. Avoid collecting dangerous organisms, such as wasps, scorpions, and snake; and poisonous plants, such as milkweed and oleander.
2. Avoid collecting weak or injured specimens as they will lead to incorrect observations.

Questions

1. What did you learn from the activity?
2. Why do you think it is important to classify organisms?

The Importance of Classification

Classification is important in the study of living things because of the following reasons:

1. There are millions of species of living things in the world. Grouping them makes it easier to study and identify them, because the members of the group have many characteristics in common.
2. It makes communication among biologists in the world easier.
3. It enables scientists to predict characteristics of an organism based on the characteristics of a group it belongs to. When we know the characteristics of a group then we can predict the characteristics of an organism in that group. For example, both an eagle and a chicken are birds. If we know the structure of the heart of a chicken, we can predict the structure of the heart of an eagle even if we have not seen it.
4. It helps to understand how organisms are related in terms of their evolutionary history.

Classification Systems

Task 4.2

Read from reliable online sources, library and other biology books the information about artificial and natural classification systems.

Artificial System of Classification

Artificial classification system groups organisms according to a few observable features, for example, the presence of legs or wings. Based on this, bees, birds, and bats would be grouped together because they have wings. Snakes, earthworms, and snails would also be grouped together because they do not have legs. Artificial classification system also involves the use of some other characteristics, such as size, how organisms move, where they live, or what they eat.

In the third century BC, Aristotle (a Greek philosopher) used artificial classification system to classify plants. He grouped them according to their shape, size, and their usefulness or uselessness to humans.

Advantages

• It is based on simple and easily observable features. Artificial classification is therefore straightforward and easy to use.
• It is simple to identify and classify organisms since newly discovered organisms with just a few known features can be easily fitted in.
• It is stable because it does not change with time or new discoveries.
• It is less expensive because it uses few observable features to group the organisms.
• It does not require special classification techniques or highly skilled personnel.

Disadvantages

• Some organisms that are unrelated in their internal structure such as bats and birds can be grouped together because of the resemblances of their few external features.
• Similar organisms may be placed in different groups because of the use of only few observable features, for example, bats and rats can be grouped in different groups.
• It provides only limited information about each member. For example, organisms, such as bacteria and some fungi are grouped as micro-organisms because they are microscopic. This classification ignores other features, such as modes of feeding, reproduction, and cell structure.
• It does not allow the prediction of information; hence limits more advancement in taxonomy.
• It is less accurate because it uses only few observable characteristics, such as mode of feeding, habitat, locomotion, or presence of wings.

Natural System of Classification

In the natural system of classification, organisms are grouped based on many features in common, particularly those related to evolutionary relationships. In this system, characters that show homology or similarity of origin must be distinguished from those showing analogy or similarity of use. For example, the arms of man, forelimbs of whales, and wings of birds and bats are homologous structures. In contrast, the wings of birds and wings of insects perform similar functions but they are different origins hence, they are analogous. Natural classification system uses homologous characters.

Advantages

• It allows organisms which are genetically and evolutionally related to be grouped together.
• It is more accurate, since it involves scientific research to gather enough information before the actual placement of an organism into a particular group is decided.
• It enables placing of newly discovered organisms into correct groups they belong.
• It allows addition of new features when they are discovered.

Disadvantages

• It is very expensive since it involves experiments, researches, and high level of classification skills.
• It is tedious and time consuming since it uses many features in grouping organisms.
• It is not stable because it can change any time due to discovery of new features or information.

Table 4.1: Differences between artificial and natural system of classification

Artificial System of Classification	Natural System of Classification
Considers external features only	Considers both internal and external features
Requires simple skills	Requires advanced scientific skills
Based on an individual's interest	Based on international standards
It is usually fast and less expensive	Takes more time and is expensive
Less accurate	More accurate
Has limited predictive value	Has high predictive value

Major Groups of Living Things

Task 4.3

Search from library and reliable internet sources the information on the major groups of living things and ranks of classification.

The following are the five major groups of living things that constitute the five kingdoms.

Kingdom Monera

Example: bacteria

Kingdom Protocitsta

Examples: amoeba, Plasmodium sp., and Euglena sp.

Kingdom Fungi

Examples: mushroom and yeast

Kingdom Plantae

Examples: maize, bean, and banana plants

Kingdom Animalia

Examples: human beings, dogs, and rats

However, viruses have not been included in these five kingdoms because they possess features of both living and non-living things. Examples of viruses include Corona virus, Ebola virus, and HIV.

Ranks of Classification

In classification of living things, there are seven main ranks or taxonomic units which are arranged hierarchically in a descending order from the highest to the lowest rank. Each unit is called a taxon (plural is taxa). The main taxa are Kingdom, Phylum or Division, Class, Order, Family, Genus, and Species. The highest rank is Kingdom and the lowest is Species. Hierarchical arrangement of the taxonomic units or ranks is referred to taxonomic hierarchy.

Kingdom Animalia is subdivided into phyla (singular is phylum) while kingdom Plantae is subdivided into divisions. The phyla or divisions are further subdivided into classes. Each class is subdivided into orders. An order is subdivided into families and families are subdivided into genera (singular is genus). A genus is subdivided into species. A species is a group of closely related organisms that can interbreed freely under natural conditions and produce fertile offspring.

Taxonomic Hierarchy

Kingdom Animalia → Phylum → Class → Order → Family → Genus → Species

Kingdom Plantae → Division → Class → Order → Family → Genus → Species

[Figure 4.3: Taxonomic ranks of classification]

Figure 4.3: Taxonomic ranks of classification

Kingdoms contain different varieties of organisms. At kingdom level, organisms share few features in common. As you move down the ranks, each subsequent unit has fewer organisms and the members of each unit have many features in common.

At the species level, organisms share many features. Members of the same species can interbreed to produce fertile offspring, but organisms from different species do not interbreed. If they interbreed, they do not produce fertile offspring. This is because of differences in genetic make-up, behaviour, and morphological features, such as structure of sexual organs. However, there are a few exceptions to this rule. For example, a horse and a donkey can interbreed to produce a mule. Mules are usually but not always infertile. Dogs and wolves can interbreed to produce fertile offspring.

Classification of Some Common Organisms

Taxonomic Unit	Human Being	Cat	Maize Plant
Kingdom	Animalia	Animalia	Plantae
Phylum/Division	Chordata	Chordata	Angiospermophyta
Class	Mammalia	Mammalia	Monocotyledoneae
Order	Primate	Carnivora	Graminales
Family	Hominidae	Felidae	Poaceae
Genus	Homo	Felis	Zea
Species	Homo sapiens	Felis catus	Zea mays

Note: The names of higher ranks (above species) always start with a capital letter. For example, the human being is in kingdom Animalia, phylum Chordata, class Mammalia, order Primate, family Hominidae, genus Homo, and species Homo sapiens.

Binomial Nomenclature

Task 4.4

Search from the library and reliable internet sources the information about naming of organisms.

Binomial nomenclature is a scientific system of naming organisms using a two-part name. The first part of the name represents the genus. It is also called the generic name. The second part of the name represents the specific epithet. The two parts form the name of a species or scientific name. This system was first introduced by Carl Linnaeus, who is also referred to as the father of classification.

As an example, the scientific name of a human being is Homo sapiens. 'Homo' is the generic name and 'sapiens' is the specific epithet.

Rules of Binomial Nomenclature

The following rules are observed when writing scientific names:

1. All scientific names must be written in Latin language or if is in a different language, the name must be Latinised.
2. The name should have two parts; the first part represents the genus and the second part represents the specific epithet.
3. The generic name is written before the specific epithet.
4. The generic name must start with a capital letter and specific epithet begins with a small letter.
5. In published documents, such as books, scientific names should be written in italics, for example Zea mays and Homo sapiens. When handwritten, the names must be underlined separately for example, Zea mays and Homo sapiens.

Table 4.3: Scientific names of common organisms

Common Name	Scientific Name
Common frog	Rana temporaria
Domestic cat	Felis catus
Coconut palm	Cocos nucifera
Mango tree	Mangifera indica
Garlic	Allium sativum
Onion	Allium cepa
Pea plant	Pisum sativum
Housefly	Musca domestica
Lion	Panthera leo
Mimosa plant	Mimosa pudica

Chapter Summary

1. Classification is the grouping of organisms based on their similarities and differences.
2. Classification is important because:
   1. It makes it easier to identify and study the millions of organisms in the world.
   2. Each organism (species) is referred to by the same name all over the world.
   3. It is easier to study organisms when they are in groups.
   4. It enables scientists to make predictions of information.
3. There are two main system of classification systems:
   1. Artificial system of classification is based on few observable features of organisms.
   2. Natural system of classification is based on many features in common particularly those related to evolutionary relationship.
4. In natural system of classification, organisms are divided into kingdoms, phyla or divisions, classes, orders, families, genera, and species. These units are called taxa (singular is taxon).
5. The members of a species are the most closely related. They can interbreed freely under natural conditions to produce fertile offspring.
6. Currently, five kingdoms are recognised, namely Monera, Protocitsta, Fungi, Plantae, and Animalia.
7. Binomial nomenclature is the system of giving scientific names to organisms. A scientific name has two parts:
   1. The first part is the generic name.
   2. The second part is the specific epithet.

Revision Exercise 4

1. Match each item from Column A with its corresponding item in Column B.

   List A	List B
   (i) Kingdoms	(a) Natural and artificial systems
   (ii) Classification ranks	(b) Division, genus, species
   (iii) Types of classification systems	(c) Zea mays
   (iv) Scientific naming	(d) Monera, Animalia
   (v) Human being	(e) Binomial nomenclature
   (vi) Maize plant	(f) Pisum sativum
   (vii) The father of classification	(g) Felis catus
   	(h) Homo sapiens
   	(i) Aristotle
   	(j) Carl Linnaeus

2. Write TRUE for a correct statement and FALSE for an incorrect statement in the space provided.
   1. Artificial system of classification is based on few observable features. ______
   2. The process of sorting living things into groups is called classification. ______
   3. Organisms of the same species exhibit a low degree of similarity. ______
   4. The lowest rank in classification is the genus. ______
   5. Classification is based on similarities and differences among organisms. ______
3. Differentiate:
   1. Classification from taxonomy.
   2. Natural from artificial systems of classification.
4. Explain the concept of the biological species.
5. How would you apply the concept of classification in a real-world context?
6. Starting from the highest rank, outline the hierarchical ranks of classification in biology.
7. Explain why a chicken and a duck cannot interbreed even if they are kept in the same coop.
8. In a biology class, your fellow students classified pigeon and butterfly in the same group based on the presence of wings. Explain the shortcomings of their classification.
9. Diana wrote the scientific name of human beings as homosapiens. Explain why she was wrong.

Chapter Five: Viruses and Major Groups of Living Things

Introduction

There are many species of living organisms in the world. These organisms are placed in groups based on their common or shared characteristics. Each group has its own features that make it distinct from others. In this chapter, you will learn about viruses and five kingdoms of organisms, namely, Monera, Protocitista, Fungi, Plantae and Animalia. The competencies developed will enable you to distinguish members of these groups, understand their interrelationships and explore their importance to human beings and other organisms.

Think

A world without the knowledge of classification

Viruses

Task 5.1

From the library and reliable internet sources, search for information about the characteristics, advantages and disadvantages of viruses.

A virus is an extremely small fragment of nucleic acid (DNA or RNA) surrounded by a protein coat. It is smaller than a living cell. A virus is not a cell.

[Figure 5.1: Different types of viruses (a) Tobacco mosaic virus (b) Bacteriophage virus (c) Influenza virus]

Figure 5.1: Different types of viruses

Characteristics of Viruses

1. They do not have a nucleus, cytoplasm, or cell organelle.
2. They have a simple structure consisting of a small piece of nucleic acid (DNA or RNA) surrounded by a protein coat called a capsid. Some viruses have viral envelopes. These are membranes enclosing the capsids. The envelopes are made up of proteins from the host cell.
3. They cannot reproduce on their own. They must attack a host cell and use the materials in that cell to reproduce. This is called obligate parasitism. The ability of a virus to reproduce inside the cell and crystallize in the absence of a living host places them between living and non-living things.
4. When outside a host cell, they show no symptoms of life (do not grow, feed, excrete, or respire). They exist in a dormant state.
5. They are host-specific. This means that a certain type of virus attacks only a specific host. For example, the rabies virus affects only mammals and HIV attacks only certain types of white blood cells in human beings.
6. Most viruses are infectious: This means they can cause diseases to their hosts.

The Structure of Viruses

Viruses are composed of strands of genetic material (DNA or RNA) which forms the core. The core is enclosed by a protein coat called capsid as in bacteriophage. DNA or RNA are of various shapes and sizes according to the type of the virus.

[Figure 5.3: Structure of (a) Human Immunodeficiency Virus (b) Bacteriophage]

Figure 5.3: Structure of viruses

Advantages of Viruses

• Viruses are important in the study of cell and molecular Biology. They are used by scientists to manipulate and investigate the functions of cells.
• Some viruses are used to make vaccines. For example, the first vaccine against smallpox was a small dose of the virus that causes cowpox, which is a mild infection. On recovering from cowpox, the body developed antibodies that could resist both cowpox and smallpox.
• Bacteriophages are viruses that attack bacteria. They help in controlling bacterial infections and diseases.
• Some viruses are used in biological control to eradicate pests, such as insects. This is due to their characteristics of being host specific and infectious.

Disadvantages of Viruses

• Most viruses are pathogenic. They cause infections and diseases, such as tobacco mosaic disease, tomato spotted wilt disease, cassava mosaic disease, rabies, chickenpox, COVID-19, polio, and AIDS. Pathogenic viruses can reproduce very fast, leading to large-scale epidemics.
• Viruses can alter themselves often, and thus become difficult to cure viral infections. For example, there are many different types of viruses that can cause common cold and influenza.

Exercise 5.1

1. Why are viruses regarded as non-living things?
2. Explain why some viruses are used in agriculture to fight against pests and disease vectors.
3. Viruses can be regarded as a threat to human health. Explain.

Kingdom Monera

Task 5.2

From different reliable internet sources and biology books, read about the characteristics of bacteria, their advantages and disadvantages.

Kingdom Monera consists of bacteria and blue-green algae. The scientific study of bacteria is called Bacteriology.

Characteristics of Bacteria

1. They are prokaryotic as their cells lack a well-defined nucleus. Their nucleus has no nuclear membrane. They also lack other membrane bound organelles.
2. They are small unicellular organisms. Some bacteria stick together to form chains or clusters called colonies.
3. Some are free-living while others are parasites or saprophytes. Free-living bacteria means that they exist on their own. Parasitic bacteria depend on other organisms known as hosts for their needs. Examples of hosts are human beings and other animals. Saprophytic bacteria get their food from dead organic matter by external digestion.
4. Free-living bacteria and some parasitic bacteria have flagella for movement.
5. Bacteria have a slimy outer layer. This layer helps to protect them from parasites like viruses and predators, such as protozoa.
6. They reproduce asexually by binary fission or through spores.
7. They occur in various shapes. There are five known shapes of bacteria.

Shapes of Bacteria

Cocci

Spherical-shaped

Example: Streptococcus pneumoniae

Bacilli

Rod-shaped

Example: Escherichia coli

Spirilla

Spiral-shaped

Example: Treponema pallidum

Vibrio

Comma-shaped

Example: Vibrio cholerae

Spirochaetes

Spiral-shaped

Example: Borrelia sp.

Advantages of Bacteria

• Some non-pathogenic bacteria feed on substances that are harmful to the environment, and in the process neutralize them.
• Bacteria in the stomach of ruminant animals secrete cellulase enzyme that helps in digestion of cellulose.
• Nitrogen-fixing bacteria convert free nitrogen in the air into nitrates in soil which can be used by plants.
• Many bacteria are decomposers that break down dead bodies of plants and animals to release important elements.
• Some bacteria produce lactic acid important in production of cheese, yoghurt, vinegar, and alcohol.
• Some bacteria are used to produce antibiotics.
• Bacteria are used in genetic engineering to produce hormones.
• Bacteria in human gut synthesize vitamins K and B12.

Disadvantages of Bacteria

• Many bacteria cause infections and diseases in animals.
• Some bacteria cause crops diseases.
• Some bacteria cause food spoilage.
• Sulphur bacteria produce sulphuric acid, which causes damage to buried metal pipes.
• Denitrifying bacteria convert soil nitrates into atmospheric nitrogen, reducing soil fertility.

Kingdom Protocitista

Task 5.4

From the library and reliable internet sources, search information about protocitists (characteristics, advantages, and disadvantages).

Members of this kingdom include Amoeba sp., Euglena sp., Plasmodium sp., Paramecium sp., and Trypanosoma sp.

Characteristics of Protocitists

1. They are eukaryotic as they have nucleus and other membrane bound organelles.
2. Most of them are unicellular organisms.
3. Most of them live in or near water, or in moist places.
4. Some protocitists are autotrophs (manufacture their own food) while others are heterotrophs (obtain nutrients from other organisms).
5. They include mobile and sessile species.
6. Some protocitists reproduce sexually and others asexually while others reproduce both sexually and asexually.
7. Many protocitists have locomotory structures, such as cilia, flagella or pseudopodia.

Phyla of Kingdom Protocitista

Phylum Rhizopoda

Example: Amoeba sp.

Move and feed using pseudopodia

Characteristics: Free-living or parasitic, have contractile vacuoles, reproduce by binary fission

Phylum Euglenophyta

Example: Euglena sp.

Unicellular aquatic organisms with flagella

Characteristics: Have chloroplasts, protected by pellicle, have eye spot

Phylum Apicomplexa

Example: Plasmodium sp.

Unicellular parasitic organisms

Characteristics: Cause malaria, complex life cycle involving host and vector

Phylum Ciliophora

Example: Paramecium sp.

Unicellular organisms found in aquatic habitats

Characteristics: Covered with cilia, have oral groove and anal pore, heterotrophic

Phylum Zoomastigina

Example: Trypanosoma sp.

Unicellular flagellate protocitists

Characteristics: Parasitic, have undulating membrane, cause sleeping sickness

Kingdom Fungi

Task 5.7

Read from reliable internet sources, library and other biology books information about fungi.

The kingdom Fungi contains a variety of eukaryotic organisms that consist of bounded cell organelles, such as mitochondria and nucleus. Most of them are multicellular and some are unicellular. Example of unicellular fungi is yeast (Saccharomyces sp.). Examples of multicellular fungi include bread mould (Rhizopus sp.), pin mould (Mucor sp.), and mushroom (Agaricus sp.).

General Characteristics of Fungi

1. They are found in various places including air, water, soil, food, and in the bodies of animals and plants.
2. They are eukaryotic organisms with true nucleus which is enclosed in a nuclear membrane.
3. They can be either unicellular or multicellular.
4. Their body is made up of a mycelium consisting of a network of fine, tube-like filaments called hyphae (except yeast).
5. They feed saprophytically, but some of them are parasitic.
6. Some fungi form symbiotic associations with other species.
7. They reproduce both sexually by spores and asexually by budding.
8. They store carbohydrates in the form of glycogen.

Main Phyla of Kingdom Fungi

Phylum Ascomycota

Examples: Yeast, Penicillium sp.

Characteristics: Sexual spores enclosed in sac-like structures called asci, some unicellular others multicellular

Phylum Zygomycota

Examples: Bread mould, mucor

Characteristics: Have sexual spores called zygospores, grow on decaying organic materials

Phylum Basidiomycota

Examples: Mushrooms, toadstools

Characteristics: Have club-shaped structures called basidia that produce sexual spores

Advantages of Fungi

• Edible mushrooms are sources of food with high content of proteins and vitamins.
• Yeasts are used in bakeries and brewing industries.
• Used in making lactic acid, citric acid, cheese, and commercial enzymes.
• Some fungi are important in production of drugs such as penicillin.
• Used in genetic engineering and biological researches.
• Saprophytic fungi are important in decomposition of dead organisms.
• Some fungi form symbiotic relationships with plant roots (mycorrhiza).

Disadvantages of Fungi

• Some fungi cause diseases to human beings and other organisms.
• In plants, some fungi cause various diseases like potato blight and maize rust.
• Some fungi attack timber used in building houses and making furniture.
• Some parasitic fungi produce poisonous substances called mycotoxins.
• Some mushrooms are poisonous to humans when eaten.
• Some fungi cause food spoilage.

Kingdom Plantae

Kingdom Plantae is composed of a wide variety of plants. Members of this kingdom vary greatly in size, forms, habitat, means of reproduction, and morphology. Kingdom Plantae includes; moss, ferns, cone bearing plants, and flowering plants. Plants are found in various habitats, such as on land, in oceans, and in freshwater.

General Characteristics of Kingdom Plantae

1. They are multicellular and eukaryotic organisms.
2. They have cell organelles called chloroplasts that contain chlorophyll.
3. Green plants are photoautotrophs. This means that they manufacture their own food using sunlight through the process of photosynthesis.
4. Some plants reproduce sexually through flowers or cones while others reproduce asexually by means of spores or vegetative propagation.
5. Their cells are organised into tissues, organs, and organ systems.
6. They show limited movement, for example opening and closing of flower petals and growth movements towards stimuli such as light and water.

Main Divisions of Kingdom Plantae

Division Bryophyta

Examples: Mosses, hornworts

Characteristics: Most primitive plants, no true roots/stems/leaves, depend on water for reproduction

Division Filicinophyta

Examples: Ferns, club mosses

Characteristics: Have true roots/stems/leaves, reproduce by spores, have vascular tissues

Division Coniferophyta

Examples: Pines, cedars, cypress

Characteristics: Non-flowering seed-bearing plants, produce naked seeds, bear cones

Division Angiospermophyta

Examples: Flowering plants

Characteristics: Seeds enclosed in ovaries, most diverse group, have well-developed conducting tissues

Kingdom Animalia

Task 5.9

Read from reliable internet sources and biology books the information about kingdom Animalia.

Kingdom Animalia comprises wide varieties of animals. Animals vary greatly in their structure, morphology and the way their bodies function. Kingdom Animalia includes worms, insects, and higher animals. They are found in various habitats, such as on land, in oceans, and in freshwater.

General Characteristics of Animals

1. They are eukaryotes; therefore, they possess a clearly defined nucleus and their cells have membrane bound organelles.
2. They are multicellular, that means they are made up of more than one cell.
3. They depend on other organisms as a source of their food.
4. Most animals are mobile and hence they can move from one place to another searching for shelter, food, mates, and safety.
5. Most of the animals have bilateral symmetrical bodies.
6. Most of the animals have high level of tissue differentiation and specialised body organs.
7. Most of the animals have a well-developed nervous system.
8. Most of the animals have anterior and posterior ends, with oral and anal openings.
9. The majority of the animals digest food internally in the gut and store carbohydrates in the form of glycogen.

Main Phyla of Kingdom Animalia

Phylum Platyhelminthes

Examples: Tapeworms, liver flukes

Characteristics: Flatworms, dorso-ventrally flattened bodies, some parasitic

Phylum Nematoda

Examples: Roundworms, ascaris

Characteristics: Round, cylindrical bodies, unsegmented, many parasitic

Phylum Annelida

Examples: Earthworms, leeches

Characteristics: Segmented worms, have chaetae for locomotion

Phylum Arthropoda

Examples: Insects, spiders, crabs

Characteristics: Jointed appendages, exoskeleton, segmented bodies

Phylum Chordata

Examples: Fish, frogs, birds, mammals

Characteristics: Have notochord, dorsal nerve cord, gill slits (at some stage)

Chapter Summary

1. A virus is an extremely small microscopic agent. It is not a cell.
2. Kingdom Monera consists of bacteria and blue-green algae. Bacteria can be pathogenic or non-pathogenic.
3. Kingdom Protocitista includes Amoeba sp., Plasmodium sp., Euglena sp., Paramecium sp., and Trypanosoma sp.
4. The main phyla of kingdom Fungi are: Ascomycota, Zygomycota, and Basidiomycota.
5. The main divisions of kingdom Plantae are: Bryophyta, Filicinophyta, Coniferophyta, and Angiospermophyta.
6. Vertebrates are animals that possess vertebral column. Invertebrates are animals that do not possess the vertebral column.
7. Features that differentiate members of kingdom Animalia include ability to move and possession of a well-developed nervous system.
8. Phyla of the kingdom Animalia include Platyhelminthes, Nematoda, Annelida, Arthropoda, and Chordata.

Revision Exercise 5

Choose the correct answer in questions 1-7.

1. The following are diseases caused by fungi in plants and animals EXCEPT ______.
   1. wheat rust and maize rust
   2. candidiasis
   3. influenza
   4. powdery mildew
2. Which of the following is the advantage of bryophytes?
   1. They cause fungal diseases in human beings
   2. They help to retain water in the soil
   3. They reproduced resins
   4. They are good sources of timber
3. One of the following plants is an example of conifers.
   1. Mango tree
   2. Orange tree
   3. Coconut tree
   4. Pine tree
4. Which of the following groups of organisms belong to the same Phylum?
   1. Liver fluke, hook worm, earthworm, and spider
   2. Tapeworm, earth worm, grasshopper and rat
   3. Butterfly, grasshopper, frog, and elephant
   4. Crabs, grasshopper, spider, and centipede
5. Which of the following is among the distinctive features of annelids?
   1. Their bodies have similar body segments
   2. They have a cylindrical, elongated and unsegmented body
   3. They are dorso-ventrally flattened
   4. They have suckers, hooks or both
6. Which of the following is not a distinctive feature of animals?
   1. They depend on other organisms as source of food
   2. Most of animals are capable of locomotion
   3. They have well developed nervous system
   4. They have exoskeleton
7. Which of the following is correctly matched?
   1. Platyhelminthes - segmented worms
   2. Nematoda - round worms
   3. Annelida - jointed appendages
   4. Arthropoda - flatworms
8. Write TRUE for a correct statements and FALSE for an incorrect statements in the spaces provided.
   1. A virus is an extremely small organism. ______
   2. Kingdom Monera includes Amoeba sp. ______
   3. Plasmodium sp. is a parasite that causes sleeping sickness. ______
   4. Rhizoids are found in moulds and mosses. ______
   5. Coniferophyta is one of the divisions of the Kingdom Plantae. ______
9. Explain the effects of the following organisms to humans.
   1. Entamoeba sp.
   2. Plasmodium sp.
   3. Trypanosoma sp.
10. List characteristics of phylum to which Euglena sp. belongs.
11. A bread was put in a moist cupboard. After a few days black thread-like structures which ended up in club-like structure appeared on the bread.
    1. Write the common name of the organism that grew on the bread surface.
    2. Name the kingdom to which the observed organism belongs.
    3. Name the phylum or division in which the observed organism belongs.
    4. Outline the advantages of the members of the kingdom you mentioned in (b) above.
12. What features make cockroach and human being to belong in the same kingdom?
13. Classify each of the following organisms to phylum level; (a) tape worm, (b) housefly and (c) monkey.
14. Mtakuja villagers believe that all insects are dangerous. They decided to kill them by spraying insecticide. As a biologist, convince them that insects are beneficial to their lives.

Chapter Six: Nutrition in Plants

Introduction

Plants are organisms that can manufacture their own food, and therefore are called autotrophs. Other organisms that can manufacture their own food include some bacteria and protocitists. Although plants can make their own food, they require some chemical elements from the environment. Such chemical elements are important for normal growth and development. In this chapter, you will learn about photosynthesis process and its importance, as well as the structure of a leaf in relation to photosynthesis. You will also learn roles of essential mineral elements to plants. The competencies developed will enable you to explore the importance of plant nutrition to life.

Think

The world without nutrition in plants

Concept of Nutrition

Nutrition is the process of feeding and utilising of food for energy provision, growth, development, repair and maintenance of the overall body health. Nutrition also refers to the study of the relationship between diet, health, and diseases. There are two major types of nutrition based on how organisms obtain their food. These are autotrophic nutrition and heterotrophic nutrition. In this chapter, you will learn about autotrophic nutrition.

Autotrophic Nutrition

Autotrophic nutrition is a type of nutrition in which organisms manufacture their own food using available energy sources. An organism that manufactures its own food is called an autotroph. The term 'autotroph' originates from two Greek words 'autos' which means 'self' and 'trophy' which means 'feed'; hence 'autotrophy' means 'self-feeding'. This means that autotrophs are organisms that are capable of making their own food for their own use and for other organisms. Examples of autotrophic organisms include green plants, algae, and some bacteria such as cyanobacteria.

The autotrophs can be divided into two groups based on how they obtain their energy:

Chemoautotrophs

Obtain energy from chemical substances like hydrogen sulphide, iron, methane, and ammonia. They utilize these chemicals to make their own food through chemosynthesis. Examples include some bacteria that live in harsh environments like deep sea and volcanic sites.

Photoautotrophs

Obtain energy from sunlight to make their own food. They make food using water and carbon dioxide in the presence of chlorophyll and sunlight through photosynthesis. Examples include green plants, algae, and cyanobacteria.

Photosynthesis

Task 6.1

Search from the library and reliable internet sources the information on the meaning of photosynthesis.

Photosynthesis is the process by which green plants, some bacteria and protocitists make their own food using water and carbon dioxide in the presence of sunlight energy. Organisms that make their own food are called primary producers or autotrophs. They are the primary source of food for all other organisms.

6CO₂ + 12H₂O ⟶ C₆H₁₂O₆ + 6O₂ + 6H₂O
Sunlight + Chlorophyll

During the process of photosynthesis, six molecules of carbon dioxide and twelve molecules of water combine to form one molecule of glucose (a simple sugar), six molecules of water, and six molecules of oxygen. The leaf is the main site for photosynthesis in plants. However, photosynthesis can take place in other green parts of the plant, such as stem.

Photosynthesis produces a six-carbon sugar molecule (a hexose) called glucose. Plants convert these hexose sugars into other carbohydrates, such as complex sugars, starch and cellulose. Plants are also capable of converting hexose sugars into other organic compounds, such as proteins and fats. The food formed by plants during photosynthesis is stored in the form of starch.

Biologists often use the presence of starch in some parts of plants as an indication that photosynthesis has taken place.

Structure of the Leaf in Relation to Photosynthesis

The internal and external structures of a leaf make it well adapted for photosynthesis. In most plants, the leaf is the main site for photosynthesis, although some plants, such as cactus (plural is cacti) use their stems for photosynthesis. The leaf structure provides a very efficient means for absorbing carbon dioxide and sunlight.

External Structure of a Leaf

[Figure 6.1: External structure of a leaf]

Figure 6.1: External structure of a leaf

Petiole or leaf stalk: Attaches the leaf to the branch or stem. It keeps the lamina in a position that will enable it to get maximum amount of sunlight.

Lamina or leaf blade: The expanded portion of a leaf. It has a large surface area. This maximizes the absorption of sunlight energy and carbon dioxide. The lamina is also thin so that carbon dioxide gas can diffuse and sunlight energy can penetrate over a short distance to reach cells.

Mid-rib and veins: Contain vascular tissues, namely xylem and phloem. Xylem transports water and dissolved minerals while phloem transports manufactured food in the plants.

Internal Structure of a Leaf

[Figure 6.2: Internal structure of a leaf]

Figure 6.2: Internal structure of a leaf

Cuticle: The outermost transparent and waxy layer that allows light to penetrate and protects the leaf from injury and excessive moisture loss.

Epidermis: The outermost layer of cells found on both surfaces. It is transparent and only one cell thick, allowing sunlight to penetrate easily.

Stomata: Small pores in the epidermis that allow oxygen and carbon dioxide to diffuse in and out of the leaf.

Mesophyll: Made up of palisade layer and spongy layer. The palisade cells contain chloroplasts and are the main site of photosynthesis.

Activity 6.1: Observing the external features of a leaf

Materials: Leaves from various plants, hand lens, pen or pencil, notebook and rubber

Caution: Be careful not to collect hairy or thorny leaves.

Procedure

1. Collect different plant leaves from the school or home environment.
2. Observe each of the leaves using your naked eyes.
3. Observe each of the leaf using the hand lens. Note as many details as you can.
4. Describe each of the observed leaves.
5. Explain how each of the plant parts aids photosynthesis.

Question

State the observed differences in structure among the variety of leaves.

The Process of Photosynthesis

Task 6.3

Search from reliable internet sources the simulations that show the process of photosynthesis. Note down what you have observed.

Photosynthesis takes place in cell organelles known as chloroplasts. These are mostly found in the green leaves. Chloroplasts contain chlorophyll that is responsible for trapping sunlight energy that is used during photosynthesis. Photosynthesis takes place in two stages, namely light reaction and dark reaction.

Light Reaction (Light Dependent Reaction)

This stage takes place in specialised structures of the chloroplast called grana. The grana contain chlorophyll that absorbs light energy from the sun. The light dependent reaction changes light energy into chemical energy. The formed energy is stored in a chemical compound called ATP (Adenosine Triphosphate). This energy is used in the dark reaction stage of photosynthesis.

Light energy causes photolysis, a chemical process whereby water molecules (H₂O) are split into hydrogen ions (H⁺) and hydroxyl ions (OH^-).

H₂O ⟶ H⁺ + OH^-
Light Energy

The hydroxyl ions undergo further reactions to produce water and oxygen. Some oxygen is released into the atmosphere. The rest of the oxygen is used for respiration in the plant. Hydrogen ions are used in the dark reaction stage to synthesise food together with carbon dioxide from the air.

Dark Reaction (Light Independent Reaction)

This stage takes place in the stroma in the absence of light. The stroma is a colourless matrix of fine material found in the chloroplast. During the dark reaction stage, hydrogen ions from light reaction stage and carbon dioxide from the atmosphere combine to form glucose that is the simplest carbohydrate. Glucose is later converted into starch. Starch is insoluble and acts as a temporary storage of excess carbohydrates. It can easily be converted into glucose when a plant needs energy. Glucose may also be converted into cellulose (the structural material of plants). Lipids and proteins are also formed from glucose through complex processes.

Activity 6.3: An experiment to determine the presence of starch in a leaf

Materials: A leaf, absolute ethanol, iodine solution, source of heat, test tube, beaker, dropper, forceps, water, white tile, cotton wool, notebook, and pencil

Procedure

1. Take a leaf from a plant that has been in the sunlight for at least 6 hours.
2. Put the leaf in boiling water for 2-3 minutes. This stops further chemical reactions in the leaf because boiling kills the leaf cells.
3. Put the boiled leaf in the test tube containing absolute ethanol. Cover the test tube with cotton wool. Place the test tube in a beaker of boiling water. The absolute ethanol dissolves the chlorophyll.
Caution: Do not heat absolute ethanol directly because it is highly flammable. Cover the test tube with cotton wool.
4. Remove the leaf from the absolute ethanol and rinse it in warm water. The water softens the leaf.
5. Put the leaf on a white tile. Add 2-3 drops of iodine solution on the leaf. What do you observe?
6. Record your observations.

Note: The blue-black colour indicates the presence of starch.

Importance of Photosynthesis

Task 6.4

Read from reliable internet sources and biology books information about the importance of photosynthesis.

Photosynthesis is a vital process for the continuous survival of plants and other organisms on earth. The importance of photosynthesis includes:

Production of Oxygen

Photosynthesis produces oxygen. This replenishes the atmospheric oxygen that has been used during burning, respiration, rusting, and other processes. All aerobic organisms require oxygen for respiration.

Reduction of Atmospheric CO₂

The process uses carbon dioxide from the atmosphere, reducing atmospheric CO₂ levels. Excessive CO₂ accumulation causes global warming by trapping heat escaping from the earth's surface.

Energy Conversion

Photosynthesis converts sunlight energy into chemical energy stored in organic food molecules. This energy is used by all living things for life processes.

Food Production

Photosynthesis produces food for plants. Herbivores depend directly on plants, carnivores feed on herbivores, and omnivores depend on both plants and animals as food sources.

Food Storage in Plants

The extra food produced by plants is stored in various plant organs. The stored food is used by the plants during adverse conditions, such as drought when the plant cannot synthesise adequate amounts of food. The underground storage organs of the plants are formed from modified stems, leaves or roots.

Bulb

Underground storage organ formed from modification of plant stem and leaves.

Example: Onion

Tuber

Fleshy storage organ formed from either a stem or a root.

Examples: Irish potato (stem), Sweet potato (root)

Taproot

Specialized taproots for food storage.

Examples: Carrot, Sugar beet, Beetroot

Corm

Underground storage organ formed from the plant stem.

Examples: Yams, Cocoyams, Crocuses

Rhizome

Swollen underground stem that grows horizontally.

Example: Ginger

Essential and Non-essential Elements in Plants

Task 6.5

From reliable sources read the information about the essential and non-essential elements in plants.

There are many chemical elements which are known to be important for plant growth and development. These chemical elements are divided into two major groups, namely essential and non-essential elements. The essential elements are vital for plant development and survival. The plant cannot complete its life cycle without them.

Macroelements

Required by plants in relatively large amounts. Also known as macronutrients.

Element	Functions	Deficiency Signs
Nitrogen (N)	Synthesis of proteins, formation of chlorophyll, increases seed production	Slow growth, yellowish leaves, reduced yield
Phosphorus (P)	Germination, root growth, flower and fruit production	Reduced growth, bluish-green leaves, small leaves
Potassium (K)	Steady growth, disease resistance, protein formation	Brown leaf edges, rolling leaves, disease susceptibility
Magnesium (Mg)	Formation of chlorophyll, activation of enzymes	Yellowish leaves, leaves fall without withering
Calcium (Ca)	Formation of cell walls, root growth	Poorly developed roots, curling leaf margins
Sulphur (S)	Production of protein, formation of chlorophyll	Slow growth, small stiff leaves, premature shedding

Microelements

Needed for plant growth and survival but only in very small quantities. Also called trace elements.

Element	Functions	Deficiency Signs
Boron (B)	Production of sugar and starch, water intake	Distorted growing tips, hollow stems
Copper (Cu)	Normal growth, formation of proteins	Bluish-green leaves, withering leaves
Iron (Fe)	Formation of chlorophyll, oxygen transport	Yellowing between leaf veins
Chlorine (Cl)	Plant metabolism	Wilting, stumpy roots
Manganese (Mn)	Enzyme action, chlorophyll formation	Yellowing between veins, white spots
Zinc (Zn)	Growth regulation, protein formation	Yellowing between veins, small deformed leaves

Activity 6.8: Investigating the effects of mineral elements on plant growth

Materials: Pots or tins, seeds (such as maize and beans), fertilisers containing different minerals, notebooks, and a pen

Procedure

1. Prepare pots or tins for planting seeds.
2. Plant the same types of seeds in all pots or tins.
3. Your teacher will explain what is in each type of fertiliser and the proper amounts required.
4. Vary the amounts of fertiliser that you apply in the pots or tins as follows:
   1. Do not put any fertiliser in the first pot or tin.
   2. Put adequate amounts of fertiliser in the second pot or tin.
   3. Put excess amounts of fertiliser in the third pot or tin.
5. Water all experimental pots or tins every morning and evening with the same amount of water for a period of 30 days.
6. Make daily observations of the plants in the pots or tins, including height and leaves colouration. Record the observations.

Questions

1. Is there any difference in growth of the plants in the three pots or tins? Give reasons.
2. Why was the fertiliser not applied in the first pot or tin?

Chapter Summary

1. Photosynthesis is the process by which green plants, some bacteria and some protocitists make their own food using carbon dioxide and water in the presence of sunlight.
2. A plant leaf comprises features that make it well adapted to photosynthesis:
   1. Waxy transparent cuticle
   2. Thin epidermis with stomata
   3. Palisade cells with chloroplasts
   4. Palisade cells positioned just below the upper epidermis
   5. Spongy mesophyll with air space
   6. Veins that have vascular tissue
   7. Broad flat lamina
   8. Petiole to attach the leaf to the stem
3. Photosynthesis involves two stages: light reaction stage and dark reaction stage.
4. During the light reaction stage, sunlight causes the production of ATP and splitting of water molecules into hydrogen and hydroxyl ions (photolysis).
5. In the dark reaction stage, carbon dioxide and hydrogen ions combine to form glucose (carbon dioxide fixation).
6. Plants require both macroelements and microelements to survive.
7. The macroelements include nitrogen, phosphorus, potassium, sulphur, calcium, and magnesium.
8. The microelements include boron, copper, iron, chlorine, manganese, molybdenum, and zinc.
9. Lack of necessary elements affects plant growth and crop yields. Excessive amounts also have negative effects.

Revision Exercise 6

Section A

Choose the correct answer.

1. Which of the following is NOT a type of an underground storage organ?
   1. Bulb
   2. Seed
   3. Corm
   4. Rhizome
2. The process by which plants and some bacteria use the energy from sunlight to produce glucose is called ______.
   1. Photolysis
   2. Hydrolysis
   3. Photosynthesis
   4. Plasmolysis
3. Boron, copper, iron, chlorine, manganese, molybdenum and zinc are examples of:
   1. microelements
   2. macroelements
   3. non-mineral elements
   4. organic elements
4. The part of a leaf that provides a large surface area for maximum absorption of sunlight and carbon dioxide is:
   1. petiole
   2. stomata
   3. lamina
   4. midrib
5. Write TRUE for correct statements and FALSE for incorrect statements in the spaces provided.
   1. The leaf is the main site for photosynthesis in plants. ______
   2. Essential elements are necessary for plant growth, development, and reproduction. ______
   3. Carbon, oxygen, hydrogen, and nitrogen are non-minerals. ______
   4. Rhizobium bacteria helps to fix nitrogen from the air into the soil. ______
   5. Microelements are needed by plants in large quantities. ______
   6. Copper is an example of trace elements. ______
   7. Lamina is the external part of a leaf while midrib is the internal part. ______
   8. A bulb is an underground storage organ formed from the plant roots. ______
   9. Sunlight energy is not needed during photosynthesis. ______
   10. Unlike carnivores, autotrophs make their own food in the form of carbohydrates. ______

Section B

6. Briefly explain the following terms.
   1. Photosynthesis
   2. Palisade mesophyll
   3. Photolysis
7. Differentiate the light reaction stage from dark reaction stage of photosynthesis.
8. Describe how a plant leaf is adapted to photosynthesis.
9. Why is photosynthesis a vital process for all living organisms?
10. Why is it necessary to destarch a leaf in an experiment investigating the importance of photosynthesis to plants?
11. Answer the following questions.
    1. Mention any two sources of sulphur in plants.
    2. Give any two signs of sulphur deficiency in plants.
    3. List down at least three functions of sulphur in plants.
    4. Why should a leaf be boiled in alcohol when testing for starch?
    5. List down the necessary conditions for photosynthesis.
12. Study the two plant leaves showing mineral deficiency and:
    1. For each of the signs shown, name the macroelement that is in limited supply.
    2. Outline the effects of excessive amounts of the macroelement stated above.
13. An agricultural officer advised farmers to apply fertiliser that contains nitrogen, phosphorous and potassium in their farms with mineral deficiency. Which signs were shown by plants that made the agricultural officer give such advice to farmers?

Chapter Seven: Nutrition in Animals

Introduction

Unlike plants that can manufacture their own food through photosynthesis, animals are heterotrophic organisms that depend on other organisms for their nutrition. Animals have evolved various feeding mechanisms and digestive systems to obtain and process nutrients from different food sources. In this chapter, you will learn about the different modes of nutrition in animals, the structure and function of the human digestive system, and the processes involved in digestion, absorption, and assimilation of food. The competencies developed will enable you to understand the importance of proper nutrition and digestive health.

Think

What would happen if animals could photosynthesize like plants?

Modes of Nutrition in Animals

Task 7.1

Search from reliable internet sources and biology books about the different modes of nutrition in animals.

Animals exhibit various modes of nutrition based on their feeding habits and the type of food they consume. The main modes of nutrition include:

Holozoic Nutrition

Animals ingest complex organic food materials which are then digested and absorbed into their bodies. This involves ingestion, digestion, absorption, assimilation, and egestion.

Examples: Humans, lions, birds

Saprophytic Nutrition

Animals feed on dead and decaying organic matter. They secrete digestive enzymes onto the food and absorb the digested products.

Examples: Earthworms, some insects, fungi

Parasitic Nutrition

Animals live on or inside other living organisms (hosts) and derive their nutrition from them, often causing harm to the host.

Examples: Tapeworms, ticks, fleas

Symbiotic Nutrition

Two different organisms live together in close association, benefiting from each other.

Examples: Termites and gut protozoa, cleaner fish and larger fish

Types of Feeding Mechanisms

Filter Feeding

Straining food particles from water

Examples: Whales, clams, flamingos

Fluid Feeding

Sucking nutrient-rich fluids from plants or animals

Examples: Mosquitoes, butterflies, leeches

Substrate Feeding

Living in or on food source

Examples: Caterpillars, maggots

Bulk Feeding

Eating large pieces of food

Examples: Humans, lions, eagles

The Human Digestive System

Task 7.2

Search from reliable internet sources the structure and functions of the human digestive system.

Structure and Functions of Digestive Organs

Organ	Structure	Function
Mouth	Contains teeth, tongue, salivary glands	Mechanical digestion (chewing), chemical digestion (saliva)
Esophagus	Muscular tube connecting mouth to stomach	Transport of food by peristalsis
Stomach	J-shaped muscular sac	Storage, mixing, protein digestion, kills bacteria
Small Intestine	Long coiled tube with villi	Complete digestion, absorption of nutrients
Large Intestine	Wider tube with no villi	Water absorption, feces formation
Liver	Large reddish-brown organ	Produces bile, detoxification, metabolism
Pancreas	Gland located behind stomach	Produces digestive enzymes and hormones

[Figure 7.1: The human digestive system]

Figure 7.1: The human digestive system

Teeth and Dental Formula

Types of Teeth and Their Functions

Type of Tooth	Function	Characteristics
Incisors	Cutting and biting	Chisel-shaped, sharp edges
Canines	Tearing and piercing	Pointed, single root
Premolars	Crushing and grinding	Two cusps, one or two roots
Molars	Grinding and chewing	Multiple cusps, two or three roots

Dental Formula

The dental formula represents the number and types of teeth in one half of the jaw. For humans:

Permanent Dentition: I 2/2 C 1/1 PM 2/2 M 3/3 = 32 teeth
Deciduous (Milk) Teeth: I 2/2 C 1/1 M 2/2 = 20 teeth

Where: I = Incisors, C = Canines, PM = Premolars, M = Molars

The formula is written for one side of the mouth, upper jaw/lower jaw.

Process of Digestion

Digestive Enzymes and Their Functions

Enzyme	Source	Substrate	Products	Optimum pH
Amylase	Salivary glands, Pancreas	Starch	Maltose	6.7-7.0
Pepsin	Stomach	Proteins	Peptides	1.5-2.0
Trypsin	Pancreas	Proteins	Peptides	7.8-8.7
Lipase	Pancreas	Lipids	Fatty acids + Glycerol	7.0-8.0
Maltase	Small intestine	Maltose	Glucose	5.0-7.0

Stages of Digestion

Mechanical Digestion

• Physical breakdown of food into smaller pieces
• Increases surface area for enzyme action
• Processes: Chewing (mouth), Churning (stomach), Segmentation (small intestine)
• No chemical changes to food molecules

Chemical Digestion

• Breakdown of complex food molecules into simpler forms
• Involves digestive enzymes and other secretions
• Processes: Hydrolysis of carbohydrates, proteins, and lipids
• Chemical bonds are broken

Absorption and Assimilation

Activity 7.1: Investigating the structure of villi

Materials: Prepared slide of small intestine section, microscope, notebook, pencil

Procedure

1. Place the prepared slide on the microscope stage.
2. Observe under low power to locate the villi.
3. Switch to high power to observe the detailed structure.
4. Draw and label what you observe.
5. Identify the following structures: villi, microvilli, blood capillaries, lacteals.

Questions

1. How does the structure of villi increase the surface area for absorption?
2. What is the function of blood capillaries and lacteals in the villi?

Adaptations of the Small Intestine for Absorption

• Great length: About 6-7 meters long providing large surface area
• Villi: Finger-like projections that increase surface area
• Microvilli: Microscopic projections on epithelial cells (brush border)
• Thin epithelium: One-cell thick for short diffusion distance
• Rich blood supply: Maintains concentration gradient
• Lacteals: For absorption of fats

Nutritional Requirements and Balanced Diet

Task 7.3

Research about the components of a balanced diet and their importance to human health.

Table 7.1: Components of a Balanced Diet

Nutrient	Function	Sources	Deficiency Diseases
Carbohydrates	Energy production	Rice, maize, potatoes, bread	Underweight, fatigue
Proteins	Growth and repair	Meat, fish, eggs, beans	Kwashiorkor, marasmus
Fats	Energy storage, insulation	Oils, butter, nuts	Dry skin, vitamin deficiency
Vitamins	Metabolic regulation	Fruits, vegetables, dairy	Various deficiency diseases
Minerals	Bone formation, enzyme function	Milk, vegetables, meat	Anemia, goiter, rickets
Water	Solvent, transport medium	Water, juices, fruits	Dehydration
Dietary Fiber	Prevents constipation	Whole grains, vegetables	Constipation, bowel diseases

Common Digestive Disorders

Dental Caries

Tooth decay caused by bacterial action on sugars producing acids that dissolve tooth enamel.

Prevention: Regular brushing, reducing sugar intake, dental check-ups

Ulcers

Open sores in the stomach or duodenum lining caused by H. pylori bacteria or excessive acid production.

Symptoms: Abdominal pain, nausea, vomiting

Constipation

Difficulty in passing feces due to hard, dry stools.

Causes: Lack of fiber, inadequate water intake, lack of exercise

Diarrhea

Frequent passing of watery feces due to reduced water absorption or increased secretion.

Causes: Bacterial infection, food poisoning, lactose intolerance

Chapter Summary

1. Animals are heterotrophic organisms that depend on other organisms for nutrition.
2. Main modes of nutrition in animals include holozoic, saprophytic, parasitic, and symbiotic nutrition.
3. Feeding mechanisms include filter feeding, fluid feeding, substrate feeding, and bulk feeding.
4. The human digestive system consists of the alimentary canal and accessory organs.
5. Human teeth include incisors, canines, premolars, and molars with specific functions.
6. The dental formula for permanent teeth is I2/2 C1/1 PM2/2 M3/3.
7. Digestion involves both mechanical and chemical processes.
8. Digestive enzymes break down carbohydrates, proteins, and lipids into absorbable units.
9. The small intestine is adapted for absorption through villi, microvilli, and rich blood supply.
10. A balanced diet includes carbohydrates, proteins, fats, vitamins, minerals, water, and dietary fiber.
11. Common digestive disorders include dental caries, ulcers, constipation, and diarrhea.
12. Proper nutrition and digestive health are essential for overall well-being.

Revision Exercise 7

1. Differentiate between the following terms:
   1. Holozoic nutrition and saprophytic nutrition
   2. Mechanical digestion and chemical digestion
   3. Absorption and assimilation
2. Name the types of human teeth and state one function of each.
3. Write the dental formula for:
   1. Permanent dentition in humans
   2. Deciduous teeth in humans
4. Complete the following table for digestive enzymes:

   Enzyme	Source	Substrate	Products
   Amylase
   Pepsin
   Lipase

5. Describe five adaptations of the small intestine for absorption of nutrients.
6. Explain why the stomach does not digest itself despite producing strong acids and enzymes.
7. List the seven components of a balanced diet and state one function of each.
8. Name two common digestive disorders and suggest ways to prevent each.
9. Design a balanced meal for a 15-year-old student and explain why it is balanced.
10. Explain the importance of dietary fiber in human nutrition.
11. Describe the pathway of food through the human digestive system, naming all organs in order.
12. Why is the liver considered an important organ in digestion even though food doesn't pass through it?
13. A student complains of frequent stomach aches after drinking milk. What could be the possible cause and what advice would you give?
14. Compare and contrast the digestive systems of herbivores and carnivores.
15. Explain how the structure of villi in the small intestine is related to their function.

Chapter Eight: Transport in Plants and Animals

Introduction

Living organisms require efficient transport systems to move substances within their bodies. Plants and animals have evolved different but equally effective mechanisms for transporting water, nutrients, gases, and other essential materials. While plants rely on vascular tissues for transport, animals have developed complex circulatory systems. In this chapter, you will learn about the structure and function of transport systems in both plants and animals, the processes involved, and the importance of these systems for survival. The competencies developed will enable you to understand how organisms maintain internal balance and respond to their environments.

Think

How would plants and animals survive without transport systems?

Need for Transport Systems

Task 8.1

Research and explain why multicellular organisms need specialized transport systems while unicellular organisms do not.

In Unicellular Organisms

• Small size provides large surface area to volume ratio
• Substances can diffuse directly through cell membrane
• Short diffusion distances
• No specialized transport system needed
• Examples: Amoeba, Paramecium, bacteria

In Multicellular Organisms

• Large size provides small surface area to volume ratio
• Long diffusion distances to internal cells
• High metabolic demands
• Specialized transport systems required
• Examples: Humans, trees, elephants

Transport in Plants

Plant Vascular Tissues

Xylem Tissue

Function: Transport of water and mineral salts from roots to leaves

Direction: Upward only (unidirectional)

Components:

• Vessels - dead, hollow cells
• Tracheids - tapered cells with pits
• Xylem fibers - for support
• Xylem parenchyma - living cells

Phloem Tissue

Function: Transport of manufactured food (sucrose, amino acids)

Direction: Bidirectional (up and down)

Components:

• Sieve tubes - living cells without nuclei
• Companion cells - control sieve tubes
• Phloem fibers - for support
• Phloem parenchyma - storage

Mechanisms of Water Transport in Plants

Root Pressure

Water entering root hairs creates pressure that pushes water upward in xylem vessels.

Capillarity

Water moves upward in narrow tubes due to adhesive and cohesive forces.

Transpiration Pull

Evaporation of water from leaves creates suction that pulls water upward through xylem.

Activity 8.1: Demonstrating water transport in plants

Materials: Fresh celery stalk with leaves, red food coloring, beaker, water, sharp knife

Procedure

1. Fill a beaker with water and add several drops of red food coloring.
2. Place the celery stalk in the colored water.
3. Leave it for 24 hours in a well-lit area.
4. Remove the celery and cut across the stem with a sharp knife.
5. Observe the distribution of red color in the stem.

Safety precaution: Be careful when using sharp knives.

Questions

1. Which tissues are stained red? Why?
2. What does this experiment demonstrate about water transport in plants?
3. How does this relate to the transpiration stream?

Transpiration and Its Importance

Task 8.2

Investigate factors that affect the rate of transpiration in plants.

Table 8.1: Factors Affecting Transpiration Rate

Factor	Effect on Transpiration	Explanation
Temperature	Increases	Higher temperature increases evaporation rate
Humidity	Decreases	High humidity reduces water vapor gradient
Wind speed	Increases	Wind removes water vapor from leaf surface
Light intensity	Increases	Light causes stomata to open
Soil water	Decreases when low	Limited water supply reduces transpiration

Importance of Transpiration

• Cooling effect: Evaporation cools the plant
• Mineral transport: Helps move minerals from roots to leaves
• Water movement: Maintains transpiration pull
• Turgor pressure: Maintains cell rigidity

Transport in Animals

Types of Circulatory Systems

Open Circulatory System

Characteristics:

• Blood flows freely in body cavities
• No distinction between blood and interstitial fluid
• Lower pressure system
• Less efficient

Examples: Insects, spiders, crustaceans

Closed Circulatory System

Characteristics:

• Blood confined to blood vessels
• Distinct blood and interstitial fluid
• Higher pressure system
• More efficient

Examples: Humans, birds, fish, earthworms

The Human Circulatory System

[Figure 8.1: The human circulatory system]

Figure 8.1: The human circulatory system

Components of Human Circulatory System

Component	Structure	Function
Heart	Four-chambered muscular pump	Pumps blood throughout the body
Arteries	Thick, muscular, elastic walls	Carry blood away from heart
Veins	Thin walls with valves	Carry blood toward heart
Capillaries	Very thin, one-cell thick walls	Site of substance exchange
Blood	Fluid connective tissue	Transport medium

Composition of Blood

Component	Percentage	Function
Plasma	55%	Liquid medium, transports nutrients, hormones, waste
Red Blood Cells	45%	Transport oxygen (contain hemoglobin)
White Blood Cells	<1%	Defense against pathogens
Platelets	<1%	Blood clotting

The Heart and Blood Circulation

Pathway of Blood Through the Heart

1. Deoxygenated blood enters right atrium via vena cava
2. Blood passes through tricuspid valve to right ventricle
3. Right ventricle pumps blood to lungs via pulmonary artery
4. Oxygenated blood returns to left atrium via pulmonary veins
5. Blood passes through bicuspid valve to left ventricle
6. Left ventricle pumps oxygenated blood to body via aorta

Types of Blood Circulation

Pulmonary Circulation

Path: Heart → Lungs → Heart

Function: Oxygenation of blood

Blood vessels: Pulmonary arteries and veins

Systemic Circulation

Path: Heart → Body → Heart

Function: Deliver oxygen and nutrients to tissues

Blood vessels: Aorta, vena cava, and their branches

Coronary Circulation

Path: Heart → Heart muscle → Heart

Function: Supply blood to heart muscle

Importance: Essential for heart function

Hepatic Portal Circulation

Path: Gut → Liver → Heart

Function: Process nutrients from digestion

Special feature: Two capillary beds

Activity 8.2: Measuring pulse rate

Materials: Stopwatch, notebook, pen

Procedure

1. Sit quietly for 5 minutes.
2. Locate your pulse on your wrist or neck.
3. Count the number of beats in 30 seconds and multiply by 2 to get beats per minute.
4. Record your resting pulse rate.
5. Do 2 minutes of exercise (jumping jacks or running in place).
6. Immediately measure and record your pulse rate after exercise.
7. Continue measuring every minute until it returns to resting rate.

Questions

1. Why does pulse rate increase during exercise?
2. What is the relationship between pulse rate and heart rate?
3. How long did it take for your pulse rate to return to normal?

Blood Groups and Transfusion

ABO Blood Group System

Blood Group	Antigens on RBC	Antibodies in Plasma	Can Donate To	Can Receive From
A	A	Anti-B	A, AB	A, O
B	B	Anti-A	B, AB	B, O
AB	A and B	None	AB	All (Universal recipient)
O	None	Anti-A and Anti-B	All (Universal donor)	O

Comparison of Plant and Animal Transport Systems

Aspect	Plants	Animals
Transport medium	Water and sap	Blood
Transport vessels	Xylem and phloem	Arteries, veins, capillaries
Pumping mechanism	Transpiration pull, root pressure	Heart
Direction of flow	Mostly one-way in xylem, two-way in phloem	Continuous circuit
Substances transported	Water, minerals, food	Oxygen, nutrients, hormones, waste
Speed of transport	Slow	Fast

Common Transport-related Disorders

In Plants

• Guttation: Loss of water droplets from leaf edges
• Wilting: Loss of turgor pressure due to water deficiency
• Xylem embolism: Air bubbles blocking xylem vessels

In Animals

• Hypertension: High blood pressure
• Atherosclerosis: Hardening of arteries
• Anemia: Low red blood cell count
• Leukemia: Cancer of white blood cells

Chapter Summary

1. Multicellular organisms require specialized transport systems due to their small surface area to volume ratio.
2. Plants have two main vascular tissues: xylem (water transport) and phloem (food transport).
3. Water moves through plants via root pressure, capillarity, and transpiration pull.
4. Transpiration is the loss of water vapor from plants and is affected by temperature, humidity, wind, and light.
5. Animals have either open or closed circulatory systems.
6. The human circulatory system consists of the heart, blood vessels, and blood.
7. Blood contains plasma, red blood cells, white blood cells, and platelets.
8. The human heart has four chambers and pumps blood through pulmonary and systemic circulation.
9. Blood groups are classified by the ABO system and Rh factor.
10. Plant and animal transport systems differ in their structures, mechanisms, and efficiency.
11. Common transport disorders include wilting in plants and cardiovascular diseases in animals.
12. Understanding transport systems helps explain how organisms maintain internal balance and respond to environmental changes.

Revision Exercise 8

1. Explain why unicellular organisms do not need specialized transport systems while multicellular organisms do.
2. Compare and contrast xylem and phloem tissues in terms of:
   1. Structure
   2. Function
   3. Direction of transport
3. Describe the three mechanisms involved in the upward movement of water in plants.
4. Design an experiment to investigate how light intensity affects the rate of transpiration in plants.
5. Differentiate between open and closed circulatory systems, giving one example of an animal with each system.
6. Trace the pathway of a red blood cell from the right atrium to the aorta, naming all chambers and valves it passes through.
7. Complete the following table about blood components:

   Blood Component	Function	Special Feature
   Red blood cells
   White blood cells
   Platelets
   Plasma

8. Explain why a person with blood group O is called a universal donor while a person with blood group AB is called a universal recipient.
9. List four factors that affect the rate of transpiration and explain how each factor influences transpiration.
10. Describe how the structure of arteries, veins, and capillaries is related to their function.
11. What would happen to a plant if its xylem vessels were blocked? Explain your answer.
12. Calculate the cardiac output of a person whose heart rate is 72 beats per minute and stroke volume is 70 mL per beat.
13. Explain the importance of the hepatic portal system in human digestion and metabolism.
14. Describe two adaptations of red blood cells for efficient oxygen transport.
15. How does exercise affect the circulatory system, and why are these changes beneficial?
16. Compare the transport of water in plants with the transport of blood in animals, highlighting three key differences.