KCSE 2024 BIOLOGY PAPER 1 MARKING SCHEME
1. The following diagram shows an apparatus used in ecological studies.

(a) Name the apparatus.
Pooter / Aspirator
(b) Why is glass preferred in the making of the part labelled E?
Glass is transparent for observation of the specimen.
2 (a) Name the Kingdom whose members are all microscopic.
Monera
(b) State two diseases caused by organisms belonging to the Kingdom named in (a) above.
Cholera. Tetanus. Tuberculosis. Typhoid
Pneumonia. Meningitis. Syphilis
3. During a microscopy practical, the following materials were provided:
a temporary mount of an onion epidermis
a transparent ruler
(a) State the aim of the experiment.
Estimate the size of the cells.
(b) Explain how the aim stated in 3(a) can be achieved. (3 marks)
Using the ruler, determine the diameter of the field of view.
Count the number of cells across the field of view.
Determine the size of one cell:
Size of one cell = Diameter of field of view in µm / Number of cells
4. The following diagram represents a specialized animal cell.

(a) Identify the cell.
Sperm cell
(b) (i) Name the cell organelle that is likely to be found in abundance in the part labelled F.
Mitochondrion
(ii) Explain the answer in 4(b)(i).
Mitochondria produce energy through respiration, which enables the cell to propel itself.
5. Name two components of blood that are absent in the tissue fluid.
Red blood cell/Erythrocytes;
Some White blood cell/Leucocytes (non-phagocytic leucocytes);
Plasma protein; Platelets/Thrombocytes;
6. Name the structures in plants through which the processes of transpiration and guttation occur.
Process | Structures in plants where it occurs |
---|---|
a) Transpiration | Stomata/stoma (Cuticle); (Lenticels) |
b) Guttation | Hydathodes |
7. Name two Classes of the Phylum Arthropoda that have a cephalothorax.
Crustacea;
Arachnida;
8. (a) Name the source of hydrochloric acid in the human alimentary canal.
Gastric glands/parietal cells/oxyntic cells;
(b) The following diagram shows a process along the mammalian digestive system.
8. (b) The following diagram shows a process along the mammalian digestive system.
(i) Name the process.
Peristalsis;
(ii) State two roles of the process in digestion.
Facilitate movement of food (along the digestive tract/system);
Enables mixing of food (down the alimentary canal);
Enables large intestines/colon/rectum to absorb water from undigested food.
Name one blood disorder caused by gene mutation.
Sickle Cell Anaemia/ Sickle cell trait; Haemophilia;
Name the stage in meiosis where each of the following processes occur:
(a) formation of spindle fibres;
Metaphase I / Metaphase II;
(b) disappearance of nucleolus.
Prophase I / Prophase II;
11. The following diagram represents part of the human male reproductive system.

11. The following diagram represents part of the human male reproductive system.
(a) Name the part labelled G.
Prostate gland;
(b) State one function of the structure labelled H.
Provides an alkaline fluid to neutralize the vaginal fluid/ Provides nourishment to the spermatozoa/ Aid in sperm movement;
(c) How is the structure labelled J adapted to its function?
Highly coiled;
To increase the S.A for the storage of the sperms;
12. How do the following structural modifications in plants minimize the rate of water loss?
(a) Leaf folding
reduces S.A. exposed (to light, temperature)
(b) Sunken stomata
water vapour is deposited in pits reducing diffusion rate
13. State two reasons for the absence of complex excretory organs in plants. (2 marks)
Waste from slowly (little waste accumulates (due to inactivity of the plants)
Some waste materials are recycled (e.g. CO2)
The wastes are less toxic
Some are stored in plant parts that are later shed off or stored in dead tissues
14. State the significance of each of the following characteristics in mammalian gaseous exchange structures and surfaces.
(a) Presence of rings of cartilage in the trachea.
Keep the trachea/wind pipe open/prevent from collapse (for gaseous exchange)
(b) Numerous blood capillaries lining the lungs.
Increase the s.a for diffusion of (respiratory) gases/increase diffusion gradient/rapid transport of (respiratory) gases/create steep concentration gradient.
15. (a) What is the most appropriate method of estimating the population of black ants in a school playing field?
Quadrat; capture-recapture method.
(b) Why are shorter food chains advantageous in an ecosystem?
They have fewer/less trophic/feeding levels; therefore, (more) energy is conserved/minimize/reduce loss of energy
16. (a) Using an example, define convergent evolution.
Is the modification of structures of organisms of different embryonic origin to perform similar functions; e.g. wings of birds/wings of bats/insects (modified for flying)/eyes of mammals and insects
16. (a) Using an example, define convergent evolution.
Is the modification of structures of organisms of different (anashal)/embryonic origin to perform similar functions; e.g. wings of insects & birds/wings of bats/insects (modified for flying)/eyes of mammals and insects
(b) Explain how natural selection is advantageous to living organisms.
It serves to identify organisms with favorable traits/adaptations that help them survive and reproduce; eliminate organisms with harmful traits (that are less likely to survive and reproduce); pass on beneficial genetic traits/mutations to subsequent generations through reproduction.
17. (a) (i) Name the blood vessel that carries oxygenated blood from the heart to the rest of the body tissues.
Aorta
17. (a) (i) Name the blood vessel that carries oxygenated blood from the heart to the rest of the body tissues.
Aorta
(ii) State the role of tricuspid valve in the mammalian heart.
Prevent backflow into the right atrium (when right ventricle muscles contract); allow flow of blood from right atrium into the right ventricle.
(b) Why are people with blood group O referred to as universal donors?
Blood group O lacks antigens/A & B; therefore,
No agglutination/with recipient antibodies
18. The following diagram shows germination in two different seedlings labelled L and M.
(a) (i) Identify the type of germination shown in seedling L.
Hypogeal
(ii) Give a reason for the answer in 18(a)(i).
The cotyledon remains below the soil surface/underground.
(b) State one common function of the parts labelled K in seedlings L and M.
Storage of food/contain digestive enzymes that break down/hydrolyse (stored) food (needed for germination).
19. The following diagram represents a longitudinal section through a phloem tissue.

(a) Account for the high concentration of mitochondria in the part labelled N. (3 marks)
To synthesize the energy
Needed for the active transport/translocation
of food substances in/out of the sieve tubes
(b) State one structural adaptation of the part labelled P to its function. (2 marks)
(b) State one structural adaptation of the part labelled P to its function. (2 marks)
Close to companion cells; for easy access of energy/nutrients
Filled with fine cytoplasmic filaments; for streaming of food from one sieve tube to another
Has organelles placed against the wall; increase S.A for packaging of filaments
Has (sieve plates) sieve pores; to allow continuous flow of materials
20. The following word equation represents a metabolic reaction taking place in an animal tissue.
Glucose → Lactic acid + Energy
(a) State the condition under which the reaction occurs. (1 mark)
In the absence of oxygen / insufficient supply of oxygen / Anaerobic conditions/ Anaerobic respiration / Anaerobiosis
(b) How does the size of an animal affect the rate of respiration? (3 marks)
Small bodied animals have larger SA:VR; exposed to higher/ faster heat loss; hence higher rate of respiration to compensate for the lost heat; (and vice versa);
21. (a) How can sexual reproduction in organisms lead to the evolution of new species? (3 marks)
Gametes (with different/gross alleles) from different parents
Fuse to form new offspring
The varied offspring pass the desirable/advantageous traits to subsequent generations
Which may finally result in the establishment of new species over a long period of time;
21. (b) State the role of continental drift in the evolution of organisms. (2 marks)
Isolation/separation of organisms (with the same genetic composition)
from the same origin to different environmental conditions
lead to the development of adaptive characteristics/traits (for successful survival in the new habitat);
22. The following diagram represents an experimental set-up used to investigate a certain biological process.(a) (i) Identify the biological process that can be investigated using the set-up. (1 mark)
Anaerobic / Fermentation / Anaerobiosis
(ii) Give a reason for the answer in 22(a)(i). (1 mark)
(ii) Give a reason for the answer in 22(a)(i). (1 mark)
Boiling removes / drives out air / oxygen / the layer
of oil prevents the entry / supply of oxygen / air
(b) Write a word equation illustrating the reaction taking place in the experiment. (1 mark)
b) Write a word equation illustrating the reaction taking place in the experiment. (1 mark)
Glucose → Alcohol / ethanol + Carbon (iv) oxide + Energy
(c) Suggest a modification on the set-up that would increase the rate of reaction in the conical flask. (1 mark)
* Increasing temperature to optimum (to activate the respiratory enzymes)
* Increasing the concentration of yeast / Glucose
* Accpt - Introducing heat
(d) Why is it necessary to cool glucose before adding yeast in the conical flask? (1 mark)
* To avoid killing the yeast cells/ denaturing the enzymes in the yeast cells/zymase
23 The following diagram represents a bone obtained from a mammalian axial skeleton.

(i) bone;
Axis
(ii) part labelled R.
Odontoid process/peg
b) Name the bones that articulate at the points labelled S and T.
S Atlas
T (other) Cervical Vertebra / 3rd cervical vertebra
24 The following food web shows a feeding relationship found in a certain ecosystem.

a) From the food web, identify the:
(i) organism with the lowest biomass;
Hawks
(ii) trophic level occupied by lizards.
Secondary consumer / 3rd trophic level
(b) Name the type of feeding relationship between the:
(i) lion and the cheetah;
(Interspecific) Competition
(ii) cheetah and the antelopes.
Predation
(c) Explain the role bacteria would play in this ecosystem.
Decomposition, for releasing / recycling of (more nutrients in the ecosystem / cleaning the environment.