Give two examples each of biodegradable and non-biodegradable wastes. Explain two practices used in sustainable waste management. State two ways in which plants help maintain the balance of carbon dioxide in the atmosphere.

Here are the answers to questions 3 and 4.

3. (a)

i) Two examples each of biodegradable and non-biodegradable wastes:

• Biodegradable wastes: Food scraps, paper.
• Non-biodegradable wastes: Plastics, glass.

ii) Two practices used in sustainable waste management:

• Recycling: Processing used materials into new products to prevent waste of potentially useful materials.
• Composting: Decomposing organic matter into a nutrient-rich soil amendment.

iii) Two ways in which plants help maintain the balance of carbon dioxide in the atmosphere:

• Photosynthesis: Plants absorb carbon dioxide from the atmosphere to produce glucose and oxygen.
• Carbon sequestration: Plants store carbon in their biomass (stems, roots, leaves), removing it from the atmosphere.

3. (b)

i) Simple machine: A device with few or no moving parts that changes the direction or magnitude of a force. Examples include levers, pulleys, and inclined planes.
Complex machine: A machine made up of two or more simple machines working together to perform a more complex task.

ii) Use of each of the following complex machines:

• Escalator: To move people between different levels in buildings.
• Crane: To lift and move heavy objects, often in construction or industrial settings.
• Bicycle: To transport people or goods over distances.

3. (c)
The four types of teeth in mammals and one function of each:

• Incisors: Used for cutting and biting food.
• Canines: Used for tearing and piercing food.
• Premolars: Used for crushing and grinding food.
• Molars: Used for grinding and chewing food.

3. (d)
Use of each of the following gardening tools:

i) Hand fork: Used for loosening soil, aerating, and removing weeds.

ii) Trowel: Used for digging small holes, transplanting seedlings, and mixing soil.

iii) Knapsack sprayer: Used for applying pesticides, herbicides, or liquid fertilizers to plants over a larger area.

4. (a)

i) Animal feed refers to food given to domestic animals, especially livestock, in the course of animal husbandry.

ii) Four different varieties of animal feed used on the farm:

• Concentrates (e.g., grains like maize, barley, or oilseed meals like soybean meal)
• Roughages (e.g., hay, silage, pasture)
• Supplements (e.g., mineral blocks, vitamin mixes)
• Forage (e.g., fresh grass, legumes)

4. (b)

i) Two structures found in the cytoplasm of a cell:

• Mitochondria
• Ribosomes (Other possible answers include Endoplasmic Reticulum, Golgi apparatus, Lysosomes, Vacuoles, Cytoskeleton)

ii) Three functions of the cytoplasm of a cell:

• It is the site of many metabolic reactions, such as glycolysis and protein synthesis.
• It holds and protects the organelles within the cell.
• It facilitates the transport of substances within the cell.

4. (c)
Two differences between salt solution and distilled water:

• Composition: Salt solution contains dissolved salts (ions), while distilled water is pure water with virtually no dissolved impurities.
• Electrical conductivity: Salt solution conducts electricity due to the presence of ions, whereas distilled water is a poor conductor of electricity.

4. (d)

i) Calculate the force $F$ applied to the box.