Question 1
- Define the term cell physiology.
- A group of students carried out an experiment to investigate a certain physiological process as shown in the diagram below.
After leaving the set up for 20 minutes, they observed that the food substance had changed to blue-black colour.
(i) Identify the reagent S
(ii) Which physiological process was being investigated? - Account for the observation made after 20 minutes.
- State the parts in the human alimentary canal where starch is digested
Answer
- Process by which cells work
- (i) Iodine solution;
(ii) Diffusion - Iodine molecules, moved by diffusion, across the semi permeable membrane, due to their small sizes;V of the visking tubing; react with starch to form a blue black colour.
- Mouth
Question 2.
Haemophilia is a sex linked disorder caused by a recessive gene. A man who is haemophilic marries a woman who is heterozygous for the disorder. Using letter H to represent the dominant gene.
- Work out the genotypes of the children from the above marriage
- What is the probability that a baby boy born to the family is haemophilic
-
(i) What is meant by the term sex-linked genes
(ii) Name two other sex-linked disorders a part from haemophilia
Answer
-
- 50%
-
(i) Genes / alleles located on the sex chromosomes and transmitted together with them
(ii) - Colour blindness;
- Hairy pinna/ nose
Question 3
The diagram below represents a feeding relationship in an ecosystem
- Name the type of ecosystem represented by the above food web
- Name the organisms in the food web that
(i)Are producers
(ii) Occupies the highest trophic level -
(i) Write a food chain that ends with the hawk as quaternary consumer
(ii) State two short term effects on the above ecosystem if all the small fish were killed - How does oil spills lead to death of fish.
- Name one other cause of water pollution apart from oil spills.
Answer
- Aquatic/ fresh wate
-
(i)Phytoplnktons
(ii) Hawks -
(i) Phytoplanktons → Zooplanktons → Frogs → Snakes → Hawks.
(ii) - Snake would decrease due to less food
- Zooplnktons would increase due to less predators -
– Oil clogs fish gills
– Oil cuts off dissolved oxygen in water leading to suffocation - Chemical from industries
Question 4
The diagram below shows a section through the mammalian skin.
- Name the parts labeled W and X.
- State the function of the parts labeled Y and Z
- Explain the changes that occur in the skin when it is cold
Answer
-
W - Sebaceous gland
X - Erector pili muscles -
Y - (malphigian layer) – Produces melanin which protects the body against the body against u.v light / determines the skin colour.
Z - (sweat gland) – Secretes sweat which evaporates to bring about cooling. -
– Vasoconstriction; hence less blood flows to the skin surface; reducing heat loss.
– No sweating; Heat produced through metabolism / shivering; is retained in the body
Question 5
The results in the table below shows the effects of some conditions necessary for seed germination. In each experiment, all other environmental conditions were kept constant, except for the one being investigated.
-
(i) What was the purpose of pyrogallic acid in experiment A
(ii) State the aim of experiment B -
(i) Account for the results obtained in experiment set up C
(ii) State why 100% germination was not achieved in experiment D - Of what biological significance is the condition necessary for germination been investigated by experiment A/D
Answer
-
(i) Absorbs Oxygen
(ii) To find out if light is necessary for germination -
(i) – At 4oc temp below optimum enzymes are inactive hence little germination
– At 60oc high temp. is low above optimum denatures enzymes / killed cells / protoplasm hence no germination
– At 35oc optimum temperatures/(w.t.t.e) hence highest % germination
(ii) Some seeds not viable -
Water
– Activates enzymes hence allowing them hydrolyse food.
– Medium for chemical reaction
– Soften testa.