**(c) Fig. 1 (c) below illustrates an experiment to demonstrate photosynthesis, the set-up was left to stand for two days before observations. Study the diagram carefully and answer the questions that
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(c) Fig. 1 (c) below illustrates an experiment to demonstrate photosynthesis, the set-up was left to stand for two days before observations. Study the diagram carefully and answer the questions that follow.
(i) Give four reasons why photosynthesis will occur in the set-up above.
1. The presence of a green plant which contains chlorophyll.
2. Availability of sunlight as an energy source.
3. Supply of water to the plant.
4. Presence of carbon dioxide in the air.
(ii) What is the role of sunlight in the process above?
Sunlight provides the energy required to convert carbon dioxide and water into glucose (food) and oxygen.
(iii) State four steps to test for the main product of photosynthesis.
The main product is starch.
1. Destarch the plant by keeping it in the dark for 24-48 hours.
2. Boil the leaf in water for a few minutes to kill the cells and break down cell walls.
3. Boil the leaf in ethanol (in a water bath) to remove chlorophyll, making the color change visible.
4. Rinse the leaf in cold water to soften it.
5. Add iodine solution to the leaf. A blue-black color indicates the presence of starch.
(iv) Name the by-product of photosynthesis and state how you would test for it.
The by-product is oxygen.
To test for oxygen, collect the gas produced and insert a glowing splint into it. The splint will relight if oxygen is present.
(d) Fig. 1 (d) below represents a cross-section through a type of teeth in humans. Study the diagram carefully and answer the questions that follow.
(i) Identify the type of teeth shown in the diagram above.
The tooth shown is a molar.
(ii) Name the parts labeled I, II, III and IV.
I: Gum* (Gingiva)
II: Root*
III: Enamel*
IV: Pulp cavity* (or Pulp)
(iii) State one function each of the parts labeled I, II, III and IV.
I (Gum): Supports and protects* the base of the tooth and the underlying bone.
II (Root): Anchors the tooth* firmly in the jawbone.
III (Enamel): Provides a hard, protective outer layer* for the crown of the tooth, resisting wear and acid erosion.
IV (Pulp cavity): Contains nerves and blood vessels* that provide nutrients to the tooth and transmit sensations like pain and temperature.
(iv) State four basic uses of the human teeth.
1. Mastication (chewing and grinding food).
2. Biting and cutting food.
3. Tearing food.
4. Speech articulation (helping to form words).
5. Maintaining facial structure and appearance.
SECTION B
(a) Describe the following components of the solar system:
(i) The sun;
The Sun is a star at the center of our solar system. It is a massive ball of hot plasma, primarily composed of hydrogen and helium, that generates light and heat through nuclear fusion. Its gravitational pull holds the planets and other celestial bodies in orbit.
(ii) The planets;
Planets are large celestial bodies that orbit a star (like the Sun), are massive enough for their own gravity to make them round, and have cleared the neighborhood around their orbit. Our solar system has eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
(iii) Asteroids.
Asteroids are rocky, airless remnants left over from the early formation of our solar system, ranging in size from a few meters to hundreds of kilometers in diameter. Most are found in the asteroid belt between Mars and Jupiter.
(b) Sodium metal is exposed to dry air.
(i) Write a word equation for the chemical reaction.
Sodium + Oxygen $\rightarrow$ Sodium oxide*
(ii) Write a balanced chemical equation for the reaction.
$$4\text{Na(s)} + \text{O}_2\text{(g)} \rightarrow 2\text{Na}_2\text{O(s)}$$
(c) Name two breeding places of mosquitoes. Describe the biological method of controlling mosquitoes.
(i) Name two breeding places of mosquitoes.
1. Stagnant water (e.g., puddles, old tires, clogged gutters, flower pots).
2. Marshes, swamps, and ponds.
(ii) Describe the biological method of controlling mosquitoes.
Biological control involves using natural enemies or biological agents to reduce mosquito populations. Examples include introducing fish (like mosquitofish) that feed on mosquito larvae in water bodies, or using bacteria such as Bacillus thuringiensis israelensis (Bti) which produce toxins that kill mosquito larvae. Another method is the release of sterile male mosquitoes to reduce reproduction.
(d) Describe two ways in which seeds can be sown on beds. List any four tools used in making vegetable beds. Give four benefits of growing vegetables.
(i) Describe two ways in which seeds can be sown on beds.
1. Broadcasting: Seeds are scattered randomly over the surface of the prepared bed. This method is often used for small seeds or when a dense crop is desired.
2. Drilling/Row sowing: Seeds are sown in straight lines or rows at specific depths and intervals. This allows for easier weeding, thinning, and harvesting.
(ii) List any four tools used in making vegetable beds.
1. Spade
2. Hoe
3. Rake
4. Trowel
5. Garden fork
6. Watering can
(iii) Give four benefits of growing vegetables.
1. Provides fresh, nutritious food directly from the garden.
2. Reduces food costs by supplementing grocery purchases.
3. Promotes physical activity and outdoor exercise.
4. Enhances food security and self-sufficiency.
5. Contributes to a healthier environment by supporting local ecosystems and reducing transportation emissions.
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