BIOLOGY PAPER 2 - FORM 4 END TERM 1 EXAMS 2020

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BIOLOGY PAPER 2 - FORM 4 END TERM 1 EXAMS 2020

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Instructions to candidates:

Answer All Questions in the Spaces Provided

The diagram shows two types of cells placed in a certain solution. Study them and answer questions that follow
1. Name the physiological process responsible for the observed results. [1 Mark]
2. Give the correct biological term used to describe cells A & B. [2 Marks]
The equation below shows a chemical reaction that takes place in plants.
Carbon (iv) oxide + water A + water
1. Identify substance A. [1 Mark]
2. Name the process represented by the equation. [1 Mark]
3. Other than the reactants state two conditions necessary for this reaction. [2 Marks]
The diagram below illustrates an experiment used to determine rate of respiration in a small insect.
1. Name the chemical compound labeled X and state its function. [2 Marks]
2. Why is the conical flask placed in a water bath? [1 Mark]
3. What would happen to the level of coloured water after 5 minutes? Explain: [2 Marks]
4. How can a control experiment be set? [1 Mark]
In a biology lesson a student collected the animal in the diagram below.
Use it to answer questions that follow;
1. Name the phylum and class to which the organism belongs
  1. Phylum ______________________________________ [1 Mark]
  2. Class________________________________________ [1 Mark]
2. Give two reasons for your answer in 1 (i), (ii) above [4 Marks]
The diagram below represents a plant in the division Byrophyta:
1. Name the parts labeled U, W, X, Y and Z [5 Marks]
2. Name one function of part labeled X, Y and Z [3 Marks]
1. It is observed that when apical bud of a plant is removed, lateral buds sprouts, where as they do not sprout in presence of the apical bud;
  1. What is the biological term used to describe this? [1 Mark]
  2. Give one application of this phenomena in agriculture. [1 Mark]
2. State four roles of IAA in plant growth and development: [4 Marks]
3. In epigeal germination the cotyledon is brought above the soil surfaces; Explain [2 Marks]
1. State 2 structural modifications of nephrons in desert mammals. [2 Marks]
2. State a kidney disease whose symptom is coloured and turbid urine [1 Mark]
In a biological experiment; a cross was made between a tall pea plant & dwarfs plants; their progeny was selfed and the resulting plants were in a mixture in the ratio of 3:1. Make a biological cross to show these outcomes. [4 Marks]
Explain geographical distribution as evidence of organic evolution. [2 Marks]

SECTION B

Answer Questions 10 (Compulsory) and either question 11 or 12 in the Spaces Provided

The table below shows the changes observed in the dry weight in milligrams of a barley seedling, its embryo and Endosperm during the first ten days after the onset of germination.

Dry weight in milligrams

Time (days)

Embryo

Endosperm

Whole seedling

0

2

41

45

2

2

39

43

4

7

32

41

6

15

21

38

8

22

11

35

10

35

6

43
1. Using a suitable scale and on the same axis, plot a graph of dry weight of embryo, endosperm and whole seedling against time. [8 Marks]
2. State and account for the changes in dry weight shown by:-
  1. Endosperm [4 Marks]
  2. Embryo [4 Marks]
3. Explain the role of water during germination [4 Marks]

1. Describe how the mammalian heart is adapted to its function [10 Marks]
2. How does gaseous exchange take place in terrestrial plants? [10 Marks]
1. How is the Epidermis of a green plant adapted to its function? [6 Marks]
2. Describe how structural factors affect rate of transpiration in plants [8 Marks]
3. Describe how xerophytes adapted to minimize water loss in their habitat. [6 Marks]

MARKING SCHEME

(a) Osmosis
(b) Flaccid; crenated

(a) glucose
(b) Photosynthesis
(c) Light, chlorophyll

(a) To absorb Co₂ produced
(b) Provides favorable temperature
(c) H₂O rises in the capillary tube; to occupy space after O₂ is used up
(d) Use a dead organism or do not include X.

(a) i) Arthropoda;
ii) Arachnida
(b) i) segmented body
Jointed appendages;
Exoskeleton
ii) 4 Pairs legs;
Head and thorax fused to form cephalothorax

(a) U – Thallus
W – Rhizoids
X – Antheridia
Y – Archegonia
Z – Capsule
(b) X – Produce male gamete
Y – Produce female gamete
Z – Produce spores

(a) i) Apical dominance
ii) Development of more branches required for increased harvest. E.g. tea & coffee.
(b) – Stimulate cell division & cell elongation bading to primary growth
– Tropic responses
– Stimulate growth of adventitious roots; from the stem
– Promotes palheno carpy;
– Induce formation of callus tissues
– Induce cell division in Cambrian leading to secondary growth.

(a) long loop of henle
Few & small glomeruli
(b) Nephritis

The earth was a single land mass; (pangea), it broke into parts that drifted away (continental drift)
Organisms that were related become separated and evolved differently;
2. (i) Weight of embryo increases steadily; cell under division; new protoplasm is synthesized; hence increase in weight;
  (ii) Decrease in weight; stored food is hydrolysed; and transported to other regions; for respiration & synthesis of new materials.
3. – Hydrolysis of stored food
  – Activation of hormones & enzymes
  – Medium for enzyme catalyzed reactions
  – Medium for transport of hydrolyzed food

(a) Gaseous Exchange
- Takes place in the spongy mesophyl during the day air diffuses in the large air spaces of the spongy mesophyll through stomata;
- The air dissolves in the thin layer of moisture over the spongy mesophyll cells; carbon dioxide from the air diffuses into the cells (photosynthetic cells) in solution form.
- Oxygen produced during photosynthesis diffuses out of the cells and out of leaves.
- At night air diffuses into the large air spaces & into the thin film of moisture over the spongy mesophyll cells
- Oxygen diffuses into the cells, Carbon(iv)oxide diffuses out of the cells into the air spaces & out of the leaf via stomata.
- Gaseous exchange also occur through the cuticle epidermis of young leaves; epidermis of root in the soil lenticels.
- In the lenticels cork cells are loosely packed; gaseous exchange occur between the loosely arranged cells & atmosphere.
(b)
- Has myogenic muscles that contract & relax rhythmically without fatigue
- Cardiac muscle fibres are interconnected to ensure rapid spread of excitation through the wall of heart ventricle walls thicker than auricle walls & generate high pressure to pump blood over a long distance
- Has coronary artery that supplies the muscles with oxygen and nutrients and remove wastes from the heart muscles
- The pericardium surrounds the heart & prevent it from over dilation
- Has semi-lunar valves that prevent blood in the arteries from flowing back into the ventricles
- Inner layer of pericardium secretes pericardial fluid that lubricates the heart.
- Outer layer of heart covered with fat that acts as shock absorber
- Has Sino arteriole node that acts as pace maker
- A longitudinal septum separates the heart into two preventing mixing of oxygenated & deoxygenated blood

1. Adaptation of Epidermis
  - Transparent to allow light to penetrate to the photosynthesis tissues
  - A single layer of cells to reduce distance over which light penetrates
  - Presence of stomata for gaseous exchange
2. Stomata
  - The higher the number the higher the rate of transpiration and vice versa
  - Location of stomata – rate is high when most are on upper leaf surface.
  - Late is lower when stomata are sunken other than exposed;
  - Some plants reverse the stomata rhythm which reduces rate of transpiration;
  Leaf size and shape
  - When a leaf is blood surface area for evaporation increases which increases rate of transpiration when leaf is narrow rate of transpiration reduces;
  Cuticle
  - when leaf has a thick waxy cuticle rate of transpiration reduces wax in water proof when cuticle is thin and not waxy rate of transpiration increases;
  Hairy leaves
  - Hairs on the leaf surface traps moisture air around the leaf is saturated with water vapour which reduces transpiration.
3. Adaptation of xerophytes
  - Have leaves that are reduced in size which reduces surface for evaporation;
  - Leaves have waxy cuticle that is thick to reduce evaporation since wax is water proof some leaves are folded to reduce number of stomata exposed to environmental factors.
  - Stomata in them are usually sunken; water vapor accumulates in these depressions preventing further water loss’
  - They have stomata whose number is greatly reduced to reduce rate of evaporation.