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
- Name the physiological process responsible for the observed results. [1 Mark]
- 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- Identify substance A. [1 Mark]
- Name the process represented by the equation. [1 Mark]
- 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.
- Name the chemical compound labeled X and state its function. [2 Marks]
- Why is the conical flask placed in a water bath? [1 Mark]
- What would happen to the level of coloured water after 5 minutes? Explain: [2 Marks]
- 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;- Name the phylum and class to which the organism belongs
- Phylum ______________________________________ [1 Mark]
- Class________________________________________ [1 Mark]
- Give two reasons for your answer in 1 (i), (ii) above [4 Marks]
- Name the phylum and class to which the organism belongs
- The diagram below represents a plant in the division Byrophyta:
- Name the parts labeled U, W, X, Y and Z [5 Marks]
- Name one function of part labeled X, Y and Z [3 Marks]
-
- 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;
- What is the biological term used to describe this? [1 Mark]
- Give one application of this phenomena in agriculture. [1 Mark]
- State four roles of IAA in plant growth and development: [4 Marks]
- In epigeal germination the cotyledon is brought above the soil surfaces; Explain [2 Marks]
- 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;
-
- State 2 structural modifications of nephrons in desert mammals. [2 Marks]
- 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
- 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]
- State and account for the changes in dry weight shown by:-
- Endosperm [4 Marks]
- Embryo [4 Marks]
- Explain the role of water during germination [4 Marks]
-
- Describe how the mammalian heart is adapted to its function [10 Marks]
- How does gaseous exchange take place in terrestrial plants? [10 Marks]
-
- How is the Epidermis of a green plant adapted to its function? [6 Marks]
- Describe how structural factors affect rate of transpiration in plants [8 Marks]
- 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; -
-
- (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. - – 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
- 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
- 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.
- 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.
- Adaptation of Epidermis
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