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Form 4 Term 2 2022 Biology Paper 2 Exam Set 30 [PDF]

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Question 1

(a) What is meant by the following terms?
 (i) Protandry
 (ii) Self sterility
(b) The diagram below shows a stage during fertilization in a plant.

 (i) Name the parts labelled Q ,R and S
 (ii) State two functions of the pollen tube
Answer
(a)  (i) Protandry: condition in which stamen/anthers of a flower mature before the carpels/pistils/stigma;
  (ii) Self sterility; pollen grains from anthers of a flower fail to germinate on the stigma of the same flower ;
(b) (i) Q - Antipodal cells/embryo sac wall;
   R - Polar nucleus/nuclei;
   S - Egg call/ovum
 (ii) Secrete enzymes that digest the stigma/style/ovary tissue; Offer passage for male nuclei to the ovum
Question 2.

(a) Explain what happens to excess amino acids in the liver of humans.
(b) Which portions of the human nephron are only found in the cortex
(c) (i) What would happen if a person produced less antidiuretic hormone
(ii) What term is given to the condition described in C (i) above
Answer
(a) Excess amino acids are deaminated/amino group is removed/amino group is converted in to ammonia; ammonia combines with carbon(iv) oxide(in the ornithine cycle) to form urea; carbohydrate group is converted into glucose for respiration/glycogen for storage;
 2NH3+CO →CO (NH3)2 +H2O
(b) Glomerulus; Bowman’s capsule; proximal convoluted tubule; distal convoluted tubule;
(c) (i) Production of large amounts of dilute urine/diuresis;
  (ii) Diabetes inspidus;
Question 3

(a) (i) What is meant by the term biological control?
 (ii) Give an example of biological control
(b) (i) What is eutrophication?
 (ii) What are the effects of eutrophication?
(c) Name a substance that is responsible for acid rain
Answer
(a) (i) Using a living organism to regulate/control/reduce/check the population of another organism;
 (ii) Catscontrolling mice; beetles controlling water hyacinth; fish in ponds controlling mosquito larvae;
Majimoto ants controlling scales; goats controlling weeds in plantations;
(b) (i) eutrophication is enrichment of water bodies with nitrates/phosphates/ammonium ions/sulphates/nutrients; due to discharge of sewage/domestic effluents/kitchen wastes containing detergents/run off water containing fertilizers; leading to rapid growth of surface plants/algae bloom/aquatic plants/phyloplanktons;
 (ii) (Proliferation of plants) block light from reaching plants underneath which will not photosynthesise; the plant die and decompose leading to depletion of oxygen/lack of oxygen ;( as a result) animals also die/suffocate (to death);
(c) Nitrogen (IV) oxide; sulphur (IV) oxide;
Question 4

Leaves are the organs of photosynthesis. The following diagram shows what happens in a plant leaf during photosynthesis

a) Give two ways in which leaves are adapted to absorb light
b) Name the gases labelled X and Y.
c) Name the tissue which transport
  (i) Water in to the leaf.
  (ii) Sugars out of the leaf.
d) Explain why it is an advantage for the plant to store carbohydrates as starch rather than as sugars.
Answer
(a) - Broad and flat to absorb maximum light;
  - Have chloroplasts which contain chlorophyll for trapping light;
  - Transparent cuticle to allow light to pass through;
  - Palisade cells are near the upper surface for optimum absorption of light;
(b)  X – Carbon (IV) oxide;
    Y – Oxygen;
(c) (i) Xylem;
  (ii) Phloem;
(d) Starch is insoluble in water; hence osmotically inactive; this reduces the effect on absorption of water
Question 5

Some millet seeds were socked in water for two days. They were then broken into small pieces and placed on the surface of agar containing starch. After two days it was found that the agar no longer contained starch
 (a) Suggest how the test for starch in the agar was carried out.
 (b) Explain why there was no starch in the agar after two days.
 (c) Why was it necessary to soak the seeds?.
 (d) Why were the millet seeds broken into small pieces
 (e) State the observation that would be made if the seeds had been soaked in boiling water?
 (f) Suggest a control experiment that would have been suitable
Answer
(a) Iodine solution was poured on the agar;
(b) Millet seeds produced amylase; that converts starch to maltose
(c) To activate the enzymes;
(d) To increase surface area for exposure of enzymes;
(e) Starch would not be digested since the enzymes would be denatured by boiling;
(f) Placing millet seeds that have not been soaked; in water on the agar/boiled millet seeds on the agar;
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- Form 4 Term 2 2022 Biology Paper 2 Exam Set 30 [PDF]