Biology Paper 2 Questions and Answers - Nginda Girls Mock Examination 2023

INSTRUCTIONS

This paper consists of TWO sections A and B.
Answer ALL questions in section A in the spaces provided
In section B answer question 6 (compulsory) and either question 7 or 8 in the spaces provided after question 8

QUESTIONS

SECTION A (40 MARKS)

In a breeding experiment a pure breed black mouse was crossed with a pure white one. All F₁ off springs were grey in color. Using letter B to represent the gene for black color and W to represent the gene for white color:
1. Give the parental genotypes. (1mark)
2. If F1 offsprings were selfed, use a genetic cross to show the phenotypic ratio of F₂ generation. (5marks)
3. Explain the presence of the grey color from the cross between a black and white mouse. (1marks)
4. Give one disadvantage of inbreeding in animal breeding. (1 mark)
The diagram below represents an organ from a bony fish. Study it and answer the questions that follow.
1. Identify the organ. (1 mark)
2. Name the part labelled R and S. (2 marks)
3. State two ways in which the structures labelled Q are adapted to their function. (2 marks)
4. Name the structure that is found covering the organ shown above. (1 mark)
5. Blood in the capillaries of the gill filaments and water flow in opposite direction. Explain the significance of this. (2marks)
The diagram below shows the bones in a human leg. Study it and answer the questions that follow.
1. Name the bone B and C. (2 marks)
2. Name the joint that is formed at the proximal end of bone C (1 mark)
3. State the function of the structure labelled A. (1 mark)
4. Name the bones that articulates with bone C at its distal end. (2 marks)
5. Distinguish between a tendon and a ligament. (2 marks)
The diagram below shows part of a longitudinal section of a young root.
1. Name the structure G and H. (2 marks)
2. State two ways in which structure F is adapted to its function. (2 marks)
3. Describe how water from the soil reaches structure J. (4marks)
1. A person had an accident that damaged some part of the brain. Name the part of the brain that was damaged that resulted in the following symptoms:
  1. Inability to regulate body temperature (1 mark)
  2. Loss of memory (1 mark)
2. State two differences between simple reflex and conditioned reflex (2 marks)
3. State the role played by the following substances during nerve impulse transmission
  1. Acetylcholine (1 mark)
  2. Cholinesterase (1 mark)
4. Give two differences between a motor neuron and relay neuron. (2 marks)

SECTION B (40 MARKS)
Answer question 6 (compulsory) and either question 7 or 8 in the spaces provided after question 8.

An experiment was set up to investigate how body temperature of a student vary with different temperature conditions of the environment. The data was tabulated as shown below.

Environmental temperature (⁰C)	0	5	10	15	20	25	30	35	40	45
Frog’s body temperature (⁰C)	5	5	10	15	20	25	30	35	40	43
Student’s body temperature (⁰C)	37	38	37	38	37	38	37	38	38	37

Using the same axis, draw graphs of the body temperature of student and frog against environmental temperature. (7 marks)
At what temperature was the body temperature of the student and frog the same? (1 mark)
Account for the shape of the graph for:
1. The frog (2 marks)
2. The student (2 marks)
State three changes that take place in the skin of the student as the environmental temperature rises. (3 marks)
State two ways in which the frog regulates its body temperature when the environmental temperature is low. (2 marks)
Give two advantages the student has over the frog. (2 marks)
Name the part of the body that detects the internal temperature of the body. (1 mark)

1. Describe the digestion and absorption of a starchy food (15 marks)
2. Describe adaptations of hydrophytes to their habitats. (5 marks)
1. Describe the structure and function of the male reproductive system. (15 marks)
2. Explain the role of water in germination. (5 marks)

MARKING SCHEME

1. BB, WW;
3. due to incomplete dominance;
4. increases chances of undesirable recessive genes expressing themselves in the phenotype;
1. Gill; rej gills
2. R- Gill rakers; rej gill raker
  S- Gill bar;
3. Thin epithelium to reduce diffusion distance;
  Numerous to increase the surface area for gaseous exchange;
  Highly vascularized to transport respiratory gases/create a steep concentration gradient for diffusion of respiratory gases; mark 1st two
4. Operculum;
5. Maintain a steep concentration gradient; for maximum gaseous exchange;
1. B-Ischium;
  C- Femur;
2. Ball and socket joint;
3. Provide surface for muscle attachment;
  Has facets for articulation with sacrum;
4. Tibia; patella;
5. Tendon is an inelastic tissue that attaches a muscle to a bone; while a ligament is an inelastic tissue that joins two bones together;
1. G- cortex;
  H-endodermis;
2. Large vacuole containing cell sap to increase osmotic pressure;
  Thin walled to shorten diffusion distance of water and mineral salts;
  Elongated to provide a large surface area for absorption; mark 1st two
3. Cell sap of the root hair cells is hypertonic to the soil solution; water molecules move from the soil into the root hair cells by osmosis; the cell sap of root hairs become diluted hence becomes less concentrated than the adjacent cortex cells; water moves into the cortex cells by osmosis; water moves from cells to cell by osmosis until it reaches the endodermis; where it is actively pumped into the xylem vessels/J; total 6mks max 4mks
  NB sequence of water flow must be followed

1. Hypothalamus;
2. Cerebrum;

Simple reflex	Conditioned reflex
Requires a stimulus to evoke the response	Requires learning through sustained repetition of the stimulus before it can evoke the response
Response is independent of previous experience	Involves modified behavior dependent on previous experience
Primary sensory and motor components remain the same throughout	Primary sensory component is replaced by a secondary sensory component but motor component does not change

1. Depolarisation of post-synaptic membrane/makes the membrane permeable/allows a nerve impulse to cross a neurojunction;
2. Breaks down acetylcholine to acetic acid and choline;

Motor neuron	Relay neuron
Has myelin sheath	Lacks myelin sheath
Cell body is on one end of the axon	Cell body is in the middle of the axon
Located outside the CNS	Located inside the CNS

2. 38.50C; +/- 0.5
  the reading should be shown on the graph a broken line
3. 1. Body temperature of frog increases as the environmental temperature increases; frog is poikilotherm/ectotherm; (hence cannot control their body temperature by homeostatic physiological/ means)
  2. Body temperature remains constant; (despite changes in the environmental temperature) humans are homoiotherms/endotherms; (hence have homeostatic physiological mechanisms to maintain their body temperature)
4. Sweat glands produce more sweat;
  Blood vessels vasodilate;
  Erector pili muscle relax and hairs lie flat on the skin; mark 1st two
5. Basking in the sun;
  Hibernation;
6. Active at all times;
  Can occupy a wide variety of habitats;
7. Hypothalamus;
1. Food is ingested through the mouth; it is chewed; to break it into smaller particles; mixed with saliva; saliva contains salivary amylase; that breaks down starch to maltose; the food is rolled (by the tongue) into boluses; and swallowed; the bolus moves by peristalsis; into the stomach; The stomach wall contract and relax mixing the food with the stomach content; the food moves to the duodenum; Pancreatic juice produced by the pancreas; is released into the duodenum. The juice contains pancreatic amylase; that digest any remaining starch to maltose; the food moves to the ileum; in the ileum intestinal juice is secreted; it contains enzyme maltase; that digests maltose to glucose; completing the process of digestion. In the ileum, the glucose is absorbed into the blood stream; by diffusion then active transport; Total 21mrks Max 15 mrks
2. Have broad leaves to increase the surface area for transpiration;
  Have many stomata on the upper surface of leaves to increase transpiration;
  Some submerged hydrophytes have threadlike leaves to provide a large surface area for absorption of maximum light for photosynthesis;
  Submerged hydrophytes have numerous and sensitive chloroplasts that photosynthesize under low light intensities;
  Have aerenchyma tissues the store air for gaseous exchange/ buoyancy;
  Flowers are raised above the water to allow for pollination;
  They have poorly developed roots that lack root hairs to reduce absorption of water; Total 7 mks max 5mks
1. Testes; produce male hormones; produce sperms;
  Scrotum; protects the testes from external mechanical damage; suspends the testes outside the body providing a cooler environment for production of sperms;
  Epididymis; stores sperms;
  Sperm duct/vas deferens; passage of sperms to the urethra;
  Urethra; passage of urine; and sperms;
  Seminal vesicle; secreted a fluid that contains nutrients for the sperms;
  Prostate glands; secretes an alkaline fluid that neutralizes the acidity along the urethra;
  Cowper’s gland; secretes an alkaline fluid that neutralizes the vaginal fluids; and activate the sperms;
  Penis; introduces sperms into the female reproductive tract; has spongy/erectile tissues that fills with blood to make the penis erect Total 22 mks max 15 mks
2. activates enzymes that hydrolyze/break down stored food;
  provides a medium for enzymes to act and break down the stored food into soluble form;
  hydrolyses and dissolve food material;
  medium of transport of dissolved food substances (to the growing regions);
  softens the seed coat to allow the radicle to emerge; (5mks)