MITIHANI POPOTE EXAMINATIONS SERIES FORM FOUR BIOLOGY EXAMINATION SERIES 1 (With Marking Scheme)

MITIHANI POPOTE EXAMINATIONS SERIES

FORM FOUR BIOLOGY EXAMINATION SERIES 1

Time: 3 Hours

Instructions:

• Answer all questions in Sections A and B.
• Answer two (2) questions from Section C.
• Use neat diagrams where applicable.

SECTION A (16 Marks)

1. Multiple Choice Questions (10 Marks)

Choose the correct answer:

1. Which of the following is a characteristic feature of Phylum Annelida?
   • a) Jointed appendages
   • b) Segmented body
   • c) Radial symmetry
   • d) Exoskeleton
2. In genetics, the term "allele" refers to:
   • a) A type of chromosome
   • b) A variant form of a gene
   • c) A cell organelle
   • d) A protein molecule
3. The theory of natural selection was proposed by:
   • a) Jean-Baptiste Lamarck
   • b) Charles Darwin
   • c) Gregor Mendel
   • d) Louis Pasteur
4. HIV primarily attacks which type of immune cells?
   • a) B cells
   • b) T-helper cells
   • c) Red blood cells
   • d) Platelets
5. Which of the following is an opportunistic infection associated with AIDS?
   • a) Malaria
   • b) Tuberculosis
   • c) Influenza
   • d) Common cold
6. PLWHA stands for:
   • a) People Living With Health Awareness
   • b) Patients Living With Human Allergy
   • c) People Living With HIV and AIDS
   • d) Protection of Life With Health Assistance
7. Which hormone is primarily responsible for growth in plants?
   • a) Insulin
   • b) Auxin
   • c) Adrenaline
   • d) Testosterone
8. The presence of homologous structures in different species is evidence of:
   • a) Convergent evolution
   • b) Divergent evolution
   • c) Artificial selection
   • d) Genetic drift
9. In humans, albinism is caused by:
   • a) A dominant allele
   • b) A recessive allele
   • c) A viral infection
   • d) A chromosomal abnormality
10. The class Insecta belongs to which phylum?
    • a) Mollusca
    • b) Arthropoda
    • c) Annelida
    • d) Chordata

2. Matching Items (6 Marks)

Match the items in List A with the correct responses in List B:

List A	List B
(i) Rhizoids	A. Female reproductive organ in moss
(ii) Sporophyte	B. Thread-like structure that anchors the moss to the ground
(iii) Capsule	C. Spore-producing structure found in the sporophyte
(iv) Protonema	D. Initial filamentous stage of moss growth from spores
(v) Archegonium	E. Male reproductive organ in moss
(vi) Antheridium	F. The diploid generation in moss life cycle responsible for spore production

SECTION B (54 Marks)

3. Phylum Chordata (10 Marks)

1. Describe three general characteristics of Phylum Chordata. (3 marks)
2. Classify the following organisms to their respective classes under Phylum Chordata:
   1. Frog
   2. Shark
   3. Pigeon
   4. Human
   (4 marks)
3. State the economic importance of any two classes under Phylum Chordata. (3 marks)

4. Genetics and Codominance (10 Marks)

1. Define the following genetic terms:
   1. Genotype
   2. Phenotype
   3. Codominance
   (3 marks)
2. In a certain plant species, red flower color (R) is codominant with white flower color (W). A cross between a red-flowered plant and a white-flowered plant produces plants with pink flowers.
   1. What is the genotype of the pink-flowered plants?
   2. If two pink-flowered plants are crossed, what would be the phenotypic ratio of their offspring? Show your working.
   (7 marks)

5. Organic Evolution (10 Marks)

1. Explain the concept of organic evolution. (2 marks)
2. Differentiate between homologous and analogous structures, giving one example of each. (4 marks)
3. State two evidences that support the theory of organic evolution. (4 marks)

6. HIV Life Cycle and AIDS (9 Marks)

1. Describe the life cycle of HIV in the human body. (5 marks)
2. Explain how the destruction of T-helper cells by HIV leads to the development of AIDS. (4 marks)

7. Opportunistic Infections and PLWHA Challenges (9 Marks)

1. Define the term "opportunistic infection" and give two examples common in PLWHA. (3 marks)
2. Discuss three challenges faced by PLWHA in society. (6 marks)

8. Human Growth and Development (9 Marks)

1. Outline the stages of human growth and development from infancy to adulthood. (5 marks)
2. Explain two internal and two external factors that affect growth in humans. (4 marks)

SECTION C (30 Marks)

Answer any two (2) questions.

9. Evidences for Organic Evolution (15 Marks)

Explain seven evidences for organic evolution.

10. Mendelian Inheritance (15 Marks)

Explain the principles of Mendelian inheritance and how they apply to monohybrid crosses. Use appropriate examples to illustrate your answer.

11. Impact of HIV/AIDS and ART (15 Marks)

Analyze the impact of HIV/AIDS on the immune system and the importance of antiretroviral therapy (ART) in managing the disease. Include the role of community support for PLWHA.

MITIHANI POPOTE EXAMINATIONS SERIES

FORM FOUR BIOLOGY EXAMINATION SERIES 1 – ANSWERS

Time: 3 Hours

SECTION A (16 Marks)

1. Multiple Choice Questions (10 Marks)

1. Which of the following is a characteristic feature of Phylum Annelida?
   • b) Segmented body
2. In genetics, the term "allele" refers to:
   • b) A variant form of a gene
3. The theory of natural selection was proposed by:
   • b) Charles Darwin
4. HIV primarily attacks which type of immune cells?
   • b) T-helper cells
5. Which of the following is an opportunistic infection associated with AIDS?
   • b) Tuberculosis
6. PLWHA stands for:
   • c) People Living With HIV and AIDS
7. Which hormone is primarily responsible for growth in plants?
   • b) Auxin
8. The presence of homologous structures in different species is evidence of:
   • b) Divergent evolution
9. In humans, albinism is caused by:
   • b) A recessive allele
10. The class Insecta belongs to which phylum?
    • b) Arthropoda

2. Matching Items (6 Marks)

List A	List B
(i) Rhizoids	B. Thread-like structure that anchors the moss to the ground
(ii) Sporophyte	F. The diploid generation in moss life cycle responsible for spore production
(iii) Capsule	C. Spore-producing structure found in the sporophyte
(iv) Protonema	D. Initial filamentous stage of moss growth from spores
(v) Archegonium	A. Female reproductive organ in moss
(vi) Antheridium	E. Male reproductive organ in moss

SECTION B (54 Marks)

3. Phylum Chordata (10 Marks)

1. Characteristics of Phylum Chordata:
   • Notochord: Flexible rod supporting the body.
   • Dorsal hollow nerve cord: Develops into the spinal cord.
   • Pharyngeal gill slits: Present at some developmental stage.
2. Classification:
   1. Frog: Class Amphibia
   2. Shark: Class Chondrichthyes
   3. Pigeon: Class Aves
   4. Human: Class Mammalia
3. Economic Importance:
   • Class Mammalia: Provide food (e.g., milk, meat) and labor (e.g., cattle).
   • Class Aves: Source of food (e.g., eggs, poultry) and pest control (e.g., birds eating insects).

4. Genetics and Codominance (10 Marks)

1. Definitions:
   1. Genotype: Genetic makeup of an organism (e.g., RR).
   2. Phenotype: Observable traits of an organism (e.g., red flowers).
   3. Codominance: Both alleles in a heterozygote are fully expressed (e.g., pink flowers in RW).
2. Codominance Cross:
   1. Genotype of pink-flowered plants: RW
   2. Phenotypic ratio of offspring (RW x RW):
      • Punnett Square: R (RW) x W (RW) yields 1 RR (red), 2 RW (pink), 1 WW (white).
      • Phenotypic ratio: 1 red : 2 pink : 1 white.

5. Organic Evolution (10 Marks)

1. Organic Evolution: Gradual change in species over time through genetic variation and natural selection.
2. Homologous vs. Analogous Structures:
   • Homologous: Same origin, different function (e.g., human arm and bat wing).
   • Analogous: Different origin, similar function (e.g., bird and insect wings).
3. Evidences for Evolution:
   • Fossil records: Show transitional forms (e.g., Archaeopteryx).
   • Comparative embryology: Similar embryonic stages (e.g., gill slits in vertebrates).

6. HIV Life Cycle and AIDS (9 Marks)

1. HIV Life Cycle:
   • HIV attaches to T-helper cells via CD4 receptors.
   • Viral RNA integrates into host DNA using reverse transcriptase.
   • Replicates, producing new virions.
   • Infected cells burst, releasing viruses.
   • Cycle repeats, spreading infection.
2. Destruction of T-helper Cells:
   • HIV destroys T-helper cells, reducing immune coordination.
   • Low T-helper count weakens immunity.
   • Opportunistic infections proliferate.
   • Progresses to AIDS, causing severe immune failure.

7. Opportunistic Infections and PLWHA Challenges (9 Marks)

1. Opportunistic Infection: Diseases exploiting weakened immunity.
   • Examples: Tuberculosis, Pneumocystis pneumonia.
2. Challenges for PLWHA:
   • Stigma: Social rejection and discrimination.
   • Access to healthcare: Limited ARV availability or cost.
   • Emotional distress: Anxiety and depression from diagnosis.

8. Human Growth and Development (9 Marks)

1. Stages:
   • Infancy: Rapid growth, motor development.
   • Childhood: Steady growth, cognitive development.
   • Adolescence: Puberty, rapid physical changes.
   • Adulthood: Physical maturity, slower growth.
   • Old age: Decline in physical functions.
2. Factors Affecting Growth:
   • Internal: Hormones (e.g., growth hormone), genetics.
   • External: Nutrition (e.g., protein intake), environment (e.g., stress).

SECTION C (30 Marks)

Answers for Questions 9 and 11.

9. Evidences for Organic Evolution (15 Marks)

• Fossil records: Show transitional forms (e.g., Tiktaalik).
• Homologous structures: Indicate common ancestry (e.g., vertebrate forelimbs).
• Analogous structures: Show convergent evolution (e.g., bird and insect wings).
• Vestigial structures: Remnants of ancestral traits (e.g., human appendix).
• Comparative embryology: Similar embryonic stages (e.g., gill slits).
• Biogeography: Species distribution reflects evolution (e.g., Galápagos finches).
• Molecular biology: DNA similarities indicate shared ancestry (e.g., cytochrome c).

11. Impact of HIV/AIDS and ART (15 Marks)

• Impact on Immune System: HIV destroys T-helper cells, leading to immune failure and AIDS.
• ART Importance: Inhibits HIV replication, restores immunity, reduces transmission.
• Community Support: Reduces stigma, provides emotional support, ensures treatment access.