END-TERM 1 2025 EXAM
PAPER 1 MARKING SCHEME
BIOLOGY FORM 4
MARKING SCHEME
Answer all the questions in the spaces provided.
1. State two characteristics of organisms that are easily observed in both animals and plants. (2 marks)
-Growth and development;
-Reproduction;
2. Fingerlings of fish were introduced to two different ponds. Those fingerlings in pond one all died
within four days but the fingerlings in pond two survived.
Suggest the likely reasons why the fingerlings in pond one died. (3 marks)
-Lack of food / algae;
-Presence of predators;
-Presence of disease causing microorganisms;
-Insufficient oxygen in water;
3. A student observing a specimen through a microscope viewed a blurred image of the specimen.
Suggest two possible reasons for this observation. (2 marks)
-Diaphragm was not fully opened;
-Mirror did not reflect enough light;
-Objective lenses not properly aligned;
-Fine adjustment knob not properly adjusted;
4. in what ways does lamarck’s theory fail to agree with modern scientific evidence. (2 marks)
-acquired characteristics to not affect genes/genetypes..
5. Distinguish between convergent and divergent evolution. (1 mark)
-Convergent evolution occurs when organisms with different ancestral origin develop analogous
structures;
-Divergent evolution occur when organisms with common ancestral origin adapt along different
lines;
6. (a) Terrestrial insects such as locusts were captured and their blood was analysed. It was found that
the blood does not have blood pigments such as haemoglobin. Explain. (2 marks)
-Insect blood does not transport respiratory gases; hence does not contain haemoglobin;
(b) State how the tracheal system in insects is adapted to gaseous exchange. (3 marks)
-Numerous to increase surface area for diffusion of gases;
-Lack chitin to allow gases to diffuse;
-Have thin epithelial lining to shorten diffusion distance;
7. State two functions of a diastema in herbivores. (2 marks)
-Provide space for tongue to move food within the mouth;
-Enables the animal to separate newly cut vegetation/food from regurgitated food;
8. a girl could clearly read a book placed 10cm away but could not identify her friend 10m away.
a. What eye defect was she suffering from? (1 mark)
-Short sightedness
b. Explain why she could not identify her friend but could read the book? (2 maarks)
-she has a longer than normal eyeball.this causes light rays from her friend 10metres away to
be focused at point in front of the retina.This results in the formation of a blurred image of
her friend on the retina.
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c.Explain how the defect can be be corrected.1mk.
-by wearing glasses with glasses with concave lenses,which diverge the light raysz outwards
beforethey reach the eye,enabling them to be focused normally on the retina.
9. Explain two ways in which the chloroplast is adapted to photosynthesis. (2 marks)
-Contains numerous chlorophyl /pigments to trap light;
-Arranged near the upper epidermis to trap maximum light;
Has enzymes;
10. The diagram shown below represent cells from a certain type of epithelial tissues in mammals.
(a) Name the part labeled V. (1 marks)
-Cilium;
(b) Identify the region of the mammalian body where the epithelial tissue maybe found. (1 mark)
Trachea / Fallopian tube / Oviduct;
(c) What is the role of the numerous mitochondria in the epithelial cells as shown above. (2 marks)
-Provide / release energy; for movement of cilia / structure V:
11. Explain what would happen to red blood cells if blood glucose concentration increased due failure of
the secretion of insulin. (3 marks)
-They lose water to plasma; by osmosis; and become creanated;
12. State three biotic factors that could affect an antelope living in Masai Mara. (3 marks)
-Competition; -Predator – prey relationships; -Diseases; -Parasitism;
13. A drop of a person’s blood shows clumping in serum of blood group B but not in serum of blood
group A.
(a) Identify the blood group of this person. (1 mark)
-A;
(b) Name the antibodies found in blood of the following groups. (2 marks)
(i) Blood group A b;
(ii) Blood group AB None;
14. list three methods used to show energy flow through the ecosystem. (3 marks)
-Food chain;
-Foodweb;
-Ecological pyramids;
15. Name three organelles that would be abundantly present in secretory cells. (3 marks)
-Endoplasmic reticulum;
-Golgi apparatus;
-Mitochondria;
16. Give three ways in which the red blood cell is adapted to transport oxygen? (3 marks)
-Lack a nucleus and most organelles to provide more room for packaging of haemoglobin to
transport oxygen;
-Biconcave to increase surface area for diffusion of oxygen into the red blood cells;
-Has numerous haemoglobin with high affinity for oxygen;
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17. Describe how the leaves of submerged plants are adapted to gaseous exchange. (3 marks)
-Leaves lack a cuticle for gases to diffuse in and out;
-Leaves have large air spaces to store air for gaseous exchange;
-Leaves are thin lamina to reduce distance for movement of gases;
18. Name the part of the seed whose growth brings about epigeal germination. (1 mark)
-Hypocotyl;
19. State three aspects of light that affect the rate of photosynthesis. (3 marks)
-Duration; -Quality; -Intensity; wavelenght
20. (a) Identify the class with organisms that have three body parts and three pairs of legs. (1 mark)
-Insecta;
(b) Suggest three reasons why members of the class named in (a) above are adapted to all types of
habitats. (3 marks)
-Show internal fertilization to increase chances of survival;
-Excreate uric acid hence can survive in any environment;
-Have a chitinous exoskeleton to protect them against water loss;
21. (a) List three types of gene mutation. (3 marks)
-Deletion; -Insertion; -Inversion; -Duplication; -Substitution;
(b) (i) What are sex-linked genes? (1 mark)
-Genes located on sex chromosome and are transmitted together with those that determine the sex of
the individual;
(ii) Name two conditions that are sex-linked. (2 marks)
-Haemophilia; -Colour blindness; -Premature baldness; -Achondroplasia;
22. (a) State any two rules of binomial nomenclature. (2 marks)
-Organism is assigned a name with two parts,generic and specific parts;
-Name is italicised in print or underlined separately when hand written;
(b) Define the term species. (2 marks)
-A group of organisms that can naturally; interbreed to produce a fertile offspring;
23. (a) Name two digestive enzymes produced in their inactive form. (2 marks)
-Pepsin; -Trypsin; pennin
(b) Explain why the enzymes named in (a) above are produced in inactive form. (2 marks)
-To prevent autolysis / digestion of cells producing it;
-To prevent digestion / breakdown of alimentary canal walls;
24. (a) Define immunity. (1 mark)
The ability of the body to resist infections;
(b) Giving an example in each case, give two main types of immunity. (4 marks)
Natural immunity; Examples – Antibodies in colostrum / antibodies from mother to foetus;
Artificial immunity; Examples – Introduction of antibodies against ………..;
25. State three advantages of cross-pollination. (3 marks) n
-mixing of genes leading to hybrid vigour resulting in higher yields ;,resistance to diseases and
new strains.
26. State three factors that increase the rate of traspiration. (3 marks)
-High temperatures; -Low humidity; -High light intensity;
