Form Four Biology Exam - Growth (Version 3) With well explained answers

FORM FOUR BIOLOGY EXAM – TOPIC: GROWTH (Version 3)

Time: 3 Hours

Instructions:

• Answer all questions in Sections A and B.
• Answer two (2) questions only from Section C.
• Write your answers clearly.

SECTION A (16 Marks)

1. Multiple Choice Questions (10 Marks)

Choose the correct answer and write its letter:

1. Which of the following is a characteristic of determinate growth?
   a) Growth continues indefinitely
   b) Growth stops at maturity
   c) Occurs only in plants
   d) Involves only cell division
2. Which part of a seed contains food for the embryo?
   a) Testa
   b) Cotyledon
   c) Micropyle
   d) Plumule
3. Which condition is not necessary for seed germination?
   a) Light
   b) Water
   c) Oxygen
   d) Suitable temperature
4. Allometric growth refers to:
   a) Equal growth in all parts
   b) Growth of organs at different rates
   c) Linear increase in cell number
   d) Growth without change in shape
5. Which hormone is associated with growth in plants?
   a) Insulin
   b) Auxin
   c) Thyroxine
   d) Adrenaline
6. Which growth process allows crustaceans to increase in size?
   a) Metamorphosis
   b) Binary fission
   c) Molting
   d) Budding
7. In which stage of human development does menopause occur?
   a) Adolescence
   b) Infancy
   c) Adulthood
   d) Old age
8. What initiates germination in a dry seed?
   a) Oxygen supply
   b) Water absorption
   c) Leaf emergence
   d) Sunlight
9. Which stage is absent in incomplete metamorphosis?
   a) Larva
   b) Egg
   c) Nymph
   d) Adult
10. Which of the following is an example of complete metamorphosis?
    a) Frog
    b) Lizard
    c) Grasshopper
    d) Earthworm

2. Matching Items (6 Marks)

Match each growth-related term with its correct description:

List A	List B
I. Cotyledon	___
II. Allometric growth	___
III. Plumule	___
IV. Germination	___
V. Auxin	___
VI. Molting	___

List B:

1. Unequal growth in body parts
2. Removal of old exoskeleton
3. Growth of a seed into a seedling
4. Contains food for embryo
5. Hormone that promotes cell elongation
6. Develops into shoot system

SECTION B (54 Marks)

Answer all questions.

3.

(a) Identify four types of germination and give an example for each. (6 marks)

(b) Explain three environmental factors affecting seed germination. (3 marks)

4.

(a) John observed a young insect shedding its outer layer. Describe this process and its role in growth. (5 marks)

(b) Differentiate between direct and indirect development. (4 marks)

5.

(a) Describe the physical and psychological changes that occur during adolescence. (5 marks)

(b) Outline four differences between infancy and old age. (4 marks)

6.

(a) State four characteristics of growth in living organisms. (4 marks)

(b) Why is growth considered an irreversible process? (2 marks)

(c) Identify three structures that show continuous growth in plants. (3 marks)

7.

(a) Define metamorphosis and list its four main stages. (5 marks)

(b) Using an example, describe how metamorphosis is beneficial to survival. (4 marks)

8.

(a) Explain three ways growth is measured in animals. (3 marks)

(b) Give three importance of molting in insects and three in crustaceans. (6 marks)

SECTION C (30 Marks)

Answer two (2) questions only.

9.

Explain the types of growth in organisms, including isometric and allometric growth, and give four biological examples. (15 marks)

10.

Describe the stages of seed germination and discuss six conditions necessary for successful germination. (15 marks)

11.

Discuss the stages of human development from birth to old age and explain three changes that occur in each stage. (15 marks)

FORM FOUR BIOLOGY EXAM – TOPIC: GROWTH (Version 3) Answers

SECTION A (16 Marks)

1. Multiple Choice Questions (10 Marks)

1. Which of the following is a characteristic of determinate growth?
   b) Growth stops at maturity
   Explanation: Determinate growth ceases when an organism reaches a genetically predetermined size, typical in animals like humans, unlike indeterminate growth which continues indefinitely, mainly in plants.
2. Which part of a seed contains food for the embryo?
   b) Cotyledon
   Explanation: Cotyledons store nutrients (e.g., starch, proteins) to nourish the embryo during germination, unlike the testa (seed coat), micropyle (water entry point), or plumule (shoot precursor).
3. Which condition is not necessary for seed germination?
   a) Light
   Explanation: While water, oxygen, and suitable temperature are essential for metabolic processes in germination, light is not always required, as some seeds (e.g., beans) germinate in darkness.
4. Allometric growth refers to:
   b) Growth of organs at different rates
   Explanation: Allometric growth involves disproportionate growth, e.g., human head growing slower than the body, unlike isometric growth where all parts grow proportionally.
5. Which hormone is associated with growth in plants?
   b) Auxin
   Explanation: Auxin promotes cell elongation and differentiation in plants, unlike insulin, thyroxine, or adrenaline, which are animal hormones.
6. Which growth process allows crustaceans to increase in size?
   c) Molting
   Explanation: Molting involves shedding the exoskeleton to allow growth in crustaceans, unlike metamorphosis (structural change), binary fission (cell division), or budding (asexual reproduction).
7. In which stage of human development does menopause occur?
   d) Old age
   Explanation: Menopause, the cessation of menstruation, typically occurs in old age (around 45–55 years), marking the end of reproductive capacity.
8. What initiates germination in a dry seed?
   b) Water absorption
   Explanation: Water absorption activates enzymes, softens the seed coat, and initiates metabolic processes, unlike oxygen, sunlight, or leaf emergence, which follow later.
9. Which stage is absent in incomplete metamorphosis?
   a) Larva
   Explanation: Incomplete metamorphosis includes egg, nymph, and adult stages, but lacks the larval stage, which is characteristic of complete metamorphosis.
10. Which of the following is an example of complete metamorphosis?
    a) Frog
    Explanation: Frogs undergo complete metamorphosis (egg, tadpole, adult), unlike grasshoppers (incomplete), lizards, or earthworms (direct development).

2. Matching Items (6 Marks)

List A	List B
I. Cotyledon	d) Contains food for embryo
II. Allometric growth	a) Unequal growth in body parts
III. Plumule	f) Develops into shoot system
IV. Germination	c) Growth of a seed into a seedling
V. Auxin	e) Hormone that promotes cell elongation
VI. Molting	b) Removal of old exoskeleton

SECTION B (54 Marks)

3.

(a) Identify four types of germination and give an example for each. (6 marks)

• Epigeal germination: Cotyledons emerge above ground, becoming photosynthetic; e.g., beans (Phaseolus).
• Hypogeal germination: Cotyledons remain below ground, plumule emerges; e.g., maize (Zea mays).
• Viviparous germination: Seeds germinate while attached to the parent plant; e.g., mangroves (Rhizophora).
• Ovoviviparous germination: Seeds germinate inside the fruit before dispersal; e.g., some citrus species.

(b) Explain three environmental factors affecting seed germination. (3 marks)

• Water: Activates enzymes, softens seed coat, and facilitates nutrient transport.
• Temperature: Optimal range (e.g., 20–30°C for most plants) triggers metabolic processes.
• Oxygen: Supports aerobic respiration for energy production during germination.

4.

(a) John observed a young insect shedding its outer layer. Describe this process and its role in growth. (5 marks)

Molting is the process where an insect sheds its rigid exoskeleton to allow growth. The insect forms a new, softer exoskeleton beneath the old one, which splits and is shed. This enables body expansion, tissue development, and progression through developmental stages (e.g., larval instars to pupa). It is critical for growth as the exoskeleton restricts size increase.

(b) Differentiate between direct and indirect development. (4 marks)

• Direct development: Offspring resemble adults at birth, with no distinct larval stage; e.g., humans, reptiles.
• Indirect development: Involves distinct larval stages differing from adults, often with metamorphosis; e.g., butterflies (complete), grasshoppers (incomplete).

5.

(a) Describe the physical and psychological changes that occur during adolescence. (5 marks)

• Physical changes: Puberty triggers growth spurts, development of secondary sexual characteristics (e.g., facial hair in males, breast development in females), and reproductive organ maturation.
• Psychological changes: Increased emotional volatility, identity formation, and development of abstract thinking due to hormonal changes and brain development.

(b) Outline four differences between infancy and old age. (4 marks)

• Growth: Infancy involves rapid growth; old age involves physical decline.
• Dependency: Infants are fully dependent; elderly may have partial dependency.
• Physical ability: Infants develop motor skills; elderly experience reduced strength and mobility.
• Cognitive development: Infants learn basic skills; elderly may face cognitive decline.

6.

(a) State four characteristics of growth in living organisms. (4 marks)

• Increase in size (e.g., height, mass).
• Increase in cell number through division.
• Differentiation of cells into specialized types.
• Development of complex structures or organs.

(b) Why is growth considered учебный процесс? (2 marks)

Growth is irreversible because it involves permanent increases in cell number, size, and structural complexity, which cannot be undone without damage (e.g., cell differentiation is fixed).

(c) Identify three structures that show continuous growth in plants. (3 marks)

• Meristems (apical and lateral).
• Stems (elongation and branching).
• Roots (extension and secondary growth).

7.

(a) Define metamorphosis and list its four main stages. (5 marks)

Metamorphosis is a biological process involving significant structural and functional changes during development. Stages (complete metamorphosis): Egg, larva (e.g., caterpillar), pupa (e.g., chrysalis), adult (e.g., butterfly).

(b) Using an example, describe how metamorphosis is beneficial to survival. (4 marks)

In butterflies, metamorphosis allows larvae (caterpillars) to focus on feeding and growth, while adults focus on reproduction and dispersal. This separation reduces competition for resources and enhances survival by exploiting different ecological niches.

8.

(a) Explain three ways growth is measured in animals. (3 marks)

• Body mass: Measured using scales to track weight gain.
• Length/height: Measured with rulers or tapes (e.g., human height).
• Organ size: Measured via imaging or dissection to assess specific growth.

(b) Give three importance of molting in insects and three in crustaceans. (6 marks)

Insects:

• Allows body expansion by shedding restrictive exoskeleton.
• Facilitates developmental transitions (e.g., larva to pupa).
• Enables repair of damaged external structures.

Crustaceans:

• Permits growth in size as exoskeleton limits expansion.
• Supports regeneration of lost limbs (e.g., crab claws).
• Allows adaptation to environmental changes via new exoskeleton.

SECTION C (30 Marks)

Answer two (2) questions only.

9. Explain the types of growth in organisms, including isometric and allometric growth, and give four biological examples. (15 marks)

Types of Growth:

• Isometric growth: Proportional growth where all parts grow at the same rate, maintaining shape; e.g., growth of a jellyfish’s body.
• Allometric growth: Disproportional growth where parts grow at different rates, changing shape; e.g., human head grows slower than body during childhood.
• Determinate growth: Growth stops at maturity; e.g., human height.
• Indeterminate growth: Continuous growth throughout life; e.g., tree trunk diameter.

Biological Examples:

• Isometric: Starfish arm growth maintaining body symmetry.
• Allometric: Deer antler growth faster than body size.
• Determinate: Bird wing length fixed at adulthood.
• Indeterminate: Vine length increasing indefinitely.

10. Describe the stages of seed germination and discuss six conditions necessary for successful germination. (15 marks)

Stages of Seed Germination:

• Imbibition: Seed absorbs water, swelling and softening the seed coat.
• Activation: Enzymes are activated, breaking down stored nutrients (e.g., starch to sugars).
• Radicle emergence: The root (radicle) grows first, anchoring the seedling.
• Plumule growth: The shoot (plumule) emerges, developing into leaves and stems.

Six Conditions for Successful Germination:

• Water: Initiates metabolic processes and nutrient transport.
• Oxygen: Fuels aerobic respiration for energy.
• Temperature: Optimal range (e.g., 20–30°C) for enzyme activity.
• Viable embryo: Ensures genetic potential for growth.
• Seed coat permeability: Allows water and oxygen entry.
• Absence of inhibitors: Lack of chemicals (e.g., abscisic acid) that prevent germination.