FORM FOUR BIOLOGY EXAM – TOPIC: CLASSIFICATION OF LIVING THINGS
Time: 3 Hours
Instructions
- Answer all questions in Sections A and B.
- Answer two (2) questions only from Section C.
- All diagrams must be neat and properly labeled.
SECTION A (16 Marks)
1. Multiple Choice Questions (10 Marks).
Choose the most correct answer:
2. Matching Items (6 Marks).
Match the items in List A with the correct responses from List B:
List A
(i) Platyhelminthes
(ii) Aschelminthes
(iii) Annelida
(iv) Arthropoda
(v) Chordata
(vi) Insecta
List B
a) Presence of jointed appendages
b) Dorsoventrally flattened body
c) Segmented body with true coelom
d) Pseudocoelomate body cavity
e) Presence of notochord
f) Three pairs of legs and compound eyes
SECTION B (54 Marks)
3.
You are provided with a preserved specimen of an earthworm.
(a) Identify its phylum and class. (2 marks)
(b) List three observable features that justify its classification. (3 marks)
(c) Explain the significance of segmentation in this organism. (4 marks)
4.
A student collected a sample of a freshwater organism exhibiting bilateral symmetry, a pseudocoelom, and a complete digestive system.
(a) Identify the phylum of this organism. (2 marks)
(b) Mention two examples of organisms in this phylum. (2 marks)
(c) Describe two adaptive features of this phylum that facilitate parasitic life. (5 marks)
5.
During a field trip, students observed an organism with a segmented body, jointed appendages, and a chitinous exoskeleton.
(a) Identify the phylum and class of this organism. (2 marks)
(b) List three distinguishing features of this class. (3 marks)
(c) Explain how the exoskeleton benefits the organism. (4 marks)
6.
A dissection of a tapeworm reveals a dorsoventrally flattened body with no body cavity and distinct segments called proglottids.
(a) Identify the phylum of this organism. (2 marks)
(b) State three structural adaptations that make it suitable for parasitism. (3 marks)
(c) Explain the significance of lacking a digestive system in this organism. (4 marks)
7.
A preserved fish specimen was studied in the laboratory. It had gills, scales, and fins.
(a) To which phylum and class does the organism belong? (2 marks)
(b) List any three observable features that confirm its classification. (3 marks)
(c) State the adaptive importance of each listed feature. (4 marks)
8.
Students compared a grasshopper and a spider under a microscope.
(a) Identify their respective classes. (2 marks)
(b) Mention two distinguishing characteristics between the two classes. (2 marks)
(c) Describe the economic importance of each organism. (5 marks)
SECTION C (30 Marks)
Answer two (2) questions from this section.
9.
Discuss the major distinguishing characteristics and one example for each of the following phyla:
(a) Platyhelminthes
(b) Annelida
(c) Arthropoda
(d) Aschelminthes
(e) Chordata (15 marks)
10.
With well-labeled diagrams, describe the external features used to classify animals into different phyla. Explain how these features help organisms survive in their respective habitats. (15 marks)
11.
Describe the classification of Phylum Arthropoda into classes. For each class, state two distinguishing characteristics and give one example. (15 marks)
FORM FOUR BIOLOGY EXAM – TOPIC: CLASSIFICATION OF LIVING THINGS (With Answers)
Time: 3 Hours
Instructions
- Answer all questions in Sections A and B.
- Answer two (2) questions only from Section C.
- All diagrams must be neat and properly labeled.
SECTION A (16 Marks)
1. Multiple Choice Questions (10 Marks).
Choose the most correct answer:
2. Matching Items (6 Marks).
Match the items in List A with the correct responses from List B:
List A
(i) Platyhelminthes
(ii) Aschelminthes
(iii) Annelida
(iv) Arthropoda
(v) Chordata
(vi) Insecta
List B
a) Presence of jointed appendages
b) Dorsoventrally flattened body
c) Segmented body with true coelom
d) Pseudocoelomate body cavity
e) Presence of notochord
f) Three pairs of legs and compound eyes
- Platyhelminthes - b) Dorsoventrally flattened body
- Aschelminthes - d) Pseudocoelomate body cavity
- Annelida - c) Segmented body with true coelom
- Arthropoda - a) Presence of jointed appendages
- Chordata - e) Presence of notochord
- Insecta - f) Three pairs of legs and compound eyes
SECTION B (54 Marks)
3.
You are provided with a preserved specimen of an earthworm.
(a) Identify its phylum and class. (2 marks)
Phylum: Annelida
Class: Oligochaeta
(b) List three observable features that justify its classification. (3 marks)
- Segmented body (metameric segmentation)
- Presence of setae (bristles) for locomotion
- Closed circulatory system
- Hermaphroditic reproductive system
- Presence of clitellum (in mature specimens)
(c) Explain the significance of segmentation in this organism. (4 marks)
Segmentation (metamerism) in earthworms provides several advantages:
- Allows for specialization of body regions
- Enables more efficient and coordinated movement through independent muscle contraction in each segment
- Provides redundancy - if one segment is damaged, others can still function
- Increases body flexibility for burrowing through soil
- Facilitates greater body size without loss of mobility
4.
A student collected a sample of a freshwater organism exhibiting bilateral symmetry, a pseudocoelom, and a complete digestive system.
(a) Identify the phylum of this organism. (2 marks)
(b) Mention two examples of organisms in this phylum. (2 marks)
- Ascaris lumbricoides (roundworm)
- Wuchereria bancrofti (filarial worm)
- Ancylostoma duodenale (hookworm)
- Enterobius vermicularis (pinworm)
(c) Describe two adaptive features of this phylum that facilitate parasitic life. (5 marks)
Adaptive features of Aschelminthes for parasitic life include:
- Protective cuticle: A tough, resistant outer covering that protects against host digestive enzymes and immune responses.
- Longitudinal muscles: Allow for thrashing movements that help maintain position in host's body.
- High reproductive capacity: Produce large numbers of eggs to ensure transmission to new hosts.
- Specialized mouthparts: Hooks, teeth, or cutting plates for attachment to host tissues.
- Complex life cycles: Often involve intermediate hosts or resistant stages that enhance survival outside primary host.
5.
During a field trip, students observed an organism with a segmented body, jointed appendages, and a chitinous exoskeleton.
(a) Identify the phylum and class of this organism. (2 marks)
Phylum: Arthropoda
Class: [Depends on specific organism, could be Insecta, Arachnida, Crustacea, or Myriapoda]
(b) List three distinguishing features of this class. (3 marks)
- Body divided into head, thorax, and abdomen
- Three pairs of legs
- Typically two pairs of wings (in most adults)
- One pair of antennae
- Compound eyes
(c) Explain how the exoskeleton benefits the organism. (4 marks)
The chitinous exoskeleton provides several advantages:
- Protection: Shields against physical damage, predators, and desiccation.
- Support: Provides structural support for muscle attachment and body shape maintenance.
- Locomotion: Jointed appendages allow for precise and varied movements.
- Prevention of water loss: Waxy coating reduces dehydration in terrestrial species.
- Sensory functions: Contains sensory receptors that detect environmental changes.
6.
A dissection of a tapeworm reveals a dorsoventrally flattened body with no body cavity and distinct segments called proglottids.
(a) Identify the phylum of this organism. (2 marks)
(b) State three structural adaptations that make it suitable for parasitism. (3 marks)
- Scolex with hooks and suckers: For firm attachment to host intestinal wall.
- Absence of digestive system: Absorbs pre-digested nutrients directly through body surface.
- Proglottid segments: Each contains complete reproductive organs for massive egg production.
- Thick tegument: Resistant outer covering protects against host digestive enzymes.
- Hermaphroditism: Allows self-fertilization when only one worm is present.
(c) Explain the significance of lacking a digestive system in this organism. (4 marks)
The absence of a digestive system in tapeworms is an adaptation to their parasitic lifestyle:
- Efficient nutrient absorption: They absorb pre-digested nutrients directly from the host's intestine through their body surface (tegument).
- Space conservation: Eliminating digestive organs allows more space for reproductive structures, maximizing reproductive output.
- Reduced metabolic needs: Without digestive functions, they require less energy and can survive on minimal nutrients.
- Simplified body plan: Allows for extreme specialization for parasitic existence.
- Reduced antigenic profile: Fewer systems mean fewer potential targets for host immune responses.
7.
A preserved fish specimen was studied in the laboratory. It had gills, scales, and fins.
(a) To which phylum and class does the organism belong? (2 marks)
Phylum: Chordata
Class: Osteichthyes (or Actinopterygii for ray-finned fishes)
(b) List any three observable features that confirm its classification. (3 marks)
- Presence of gills for aquatic respiration
- Paired fins supported by bony rays
- Overlapping scales covering the body
- Lateral line system visible as a line along the body
- Streamlined body shape for aquatic locomotion
(c) State the adaptive importance of each listed feature. (4 marks)
- Gills: Extract oxygen from water for respiration in aquatic environment.
- Paired fins: Provide stability, maneuverability, and propulsion in water.
- Scales: Protect against injury, reduce friction, and prevent water loss.
- Lateral line: Detects water movements and vibrations, important for navigation and predator/prey detection.
- Streamlined body: Reduces drag while swimming, conserving energy.
8.
Students compared a grasshopper and a spider under a microscope.
(a) Identify their respective classes. (2 marks)
Grasshopper: Class Insecta
Spider: Class Arachnida
(b) Mention two distinguishing characteristics between the two classes. (2 marks)
| Feature | Insecta (Grasshopper) | Arachnida (Spider) |
|---|---|---|
| Body segments | 3 (head, thorax, abdomen) | 2 (cephalothorax, abdomen) |
| Legs | 3 pairs | 4 pairs |
| Antennae | Present (1 pair) | Absent |
| Wings | Usually present | Always absent |
(c) Describe the economic importance of each organism. (5 marks)
Grasshopper (Insecta):
- Negative: Agricultural pest that damages crops
- Positive: Food source for many animals (birds, reptiles)
- Positive: Used as food for humans in some cultures
- Positive: Important in nutrient cycling as decomposers
- Negative: Can transmit plant diseases
Spider (Arachnida):
- Positive: Natural pest control by preying on insects
- Positive: Source of venom for medical research
- Positive: Silk used in biotechnology research
- Negative: Some species are venomous to humans
- Negative: Can cause arachnophobia in some people
SECTION C (30 Marks)
Answer two (2) questions from this section.
9.
Discuss the major distinguishing characteristics and one example for each of the following phyla: (15 marks)
(a) Platyhelminthes
(b) Annelida
(c) Arthropoda
(d) Aschelminthes
(e) Chordata
(a) Phylum Platyhelminthes:
- Dorsoventrally flattened bodies (flatworms)
- Acoelomate (no body cavity)
- Incomplete digestive system (one opening)
- Most are hermaphroditic
- Example: Taenia solium (tapeworm)
(b) Phylum Annelida:
- Segmented bodies (metamerism)
- True coelom (body cavity)
- Closed circulatory system
- Setae (bristles) for locomotion
- Example: Lumbricus terrestris (earthworm)
(c) Phylum Arthropoda:
- Jointed appendages
- Chitinous exoskeleton
- Segmented body
- Open circulatory system
- Example: Periplaneta americana (cockroach)
(d) Phylum Aschelminthes (Nematoda):
- Pseudocoelomate body cavity
- Unsegmented cylindrical body
- Complete digestive tract
- Thick protective cuticle
- Example: Ascaris lumbricoides (roundworm)
(e) Phylum Chordata:
- Presence of notochord at some stage
- Dorsal hollow nerve cord
- Pharyngeal gill slits
- Post-anal tail
- Example: Homo sapiens (humans)
10.
With well-labeled diagrams, describe the external features used to classify animals into different phyla. Explain how these features help organisms survive in their respective habitats. (15 marks)
Key External Features for Classification:
- Symmetry:
- Radial (e.g., Cnidaria) - allows interaction with environment from all directions
- Bilateral (e.g., Arthropoda) - enables cephalization and directional movement
- Body Covering:
- Cuticle (Aschelminthes) - protection against harsh environments
- Exoskeleton (Arthropoda) - support and protection on land
- Scales (Chordata - fish) - reduce friction in water
- Appendages:
- Jointed legs (Arthropoda) - precise movement
- Fins (Chordata - fish) - aquatic locomotion
- Wings (Insecta) - flight capability
- Body Segmentation:
- Metamerism (Annelida) - allows specialization of body regions
- Tagmatization (Arthropoda) - fusion of segments for specific functions
Adaptive Significance:
- Aquatic Adaptations:
- Streamlined shapes reduce drag
- Gills for oxygen extraction from water
- Fins for stability and propulsion
- Terrestrial Adaptations:
- Exoskeletons prevent desiccation
- Jointed legs support body against gravity
- Tracheal systems (insects) for air breathing
- Parasitic Adaptations:
- Hooks/suckers for attachment
- Reduced sensory organs
- Thick teguments resist host defenses
Note: Diagrams would show representative organisms from major phyla with key external features labeled.
11.
Describe the classification of Phylum Arthropoda into classes. For each class, state two distinguishing characteristics and give one example. (15 marks)
| Class | Distinguishing Characteristics | Example |
|---|---|---|
| Insecta |
|
Grasshopper (Locusta migratoria) |
| Arachnida |
|
Garden spider (Araneus diadematus) |
| Crustacea |
|
Crab (Cancer pagurus) |
| Myriapoda |
|
Centipede (Scolopendra gigantea) |
| Diplopoda |
|
Millipede (Archispirostreptus gigas) |
| Chilopoda |
|
Centipede (Lithobius forficatus) |
Note: Some classification systems group Diplopoda and Chilopoda under Myriapoda as subclasses.
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