Correct Answer: B) energy

Explanation

In an ecosystem, different substances are constantly being recycled to sustain life. However, one of the options given is not recycled in an ecosystem. The options are water, energy, carbon, nitrogen, and all. Water is a very important substance in an ecosystem and is constantly being recycled through various processes such as evaporation, condensation, and precipitation. Carbon and nitrogen are also very important substances that are recycled through processes such as photosynthesis and nitrogen fixation. Energy, on the other hand, is not recycled in an ecosystem. Energy flows through an ecosystem in a one-way direction and is constantly being lost as it moves from one organism to another. This loss of energy is due to the second law of thermodynamics which states that energy cannot be recycled or reused completely. Therefore, Option B (energy) is the correct answer. It is important to note that while all the other options are recycled in an ecosystem, they are not recycled equally. Each substance has its own unique cycle and plays a vital role in sustaining life in an ecosystem. To learn more about this topic, please refer to your Biology textbook.

Correct Answer: A. extract minute soil organisms

Correct Answer: A. are warning that they may be poisonous

Explanation

(a) Structure of the cell relating to its function

(i) Sperm cell

• Has a long/whip-like tail/flagellum, with which it swims to reach the egg/ovum of the female organism.
• Has a head with acrosome; for digesting/penetrating egg membrane
• Has a nucleus in its head; which fuses with the nucleus of the ovum/egg cell during fertilisation to form zygote
• Its middle piece contains mitochondria; for supply of energy/ATP.

(ii) Palisade cell

• Has thin wall; for easy penetration of light
• Has numerous chlorosplasts in peripheral cytoplasm for maximum absorption of sunlight
• Has large vacuole containing cell sap; for temporary stor-age of products of photosynthesis.

(b) Diagram of the front view of the female reproductive system

(d) Methods of birth control in humans

• Abstinence
• Use of contraceptive pills/injection of hormonal drugs
• Coitus interruptus/withdrawal method
• Safe period/rhythm method
• Sterilization of men/vasectomy
• Sterilisation of women/tubal ligation
• Use of condoms/female condom/male condom
• Use of spermicide/foam
• Use of implant/Norplant
• Use of IUD/intra-uterine devices
• Use of diaphragm.

Correct Answer: C. AB

Correct Answer: C. plays a role in the formation of vitamin

Explanation

a.Classification of living things is the grouping/arrangement of organisms; with similar characteristics based on structural/genetic/cellular/evolutionary trends; for easy identification.

bi. -cause various plant/animal diseases;

-act as decomposers;

-recycle nutrients;

-bring about fermentation in breweries;

-used in baking industries;

-serve as source of food;

-are used in pharmaceutical industries/production of antibiotics/vitamins;

-destroy various substances/cloth/paper/wood/food

bii. -are involved in nutrient recycling;

-purify the environment/reduce greenhouse effects;

-provide shade/shelter;

-provide food;

-provide oxygen;

-prevent erosion;

-are sources of timber for building/construction;

-provide materials for pharmaceuticals/production of drugs.

c.

Correct Answer: C. liver

Explanation

(a)Conservation: Conservation is the protection/preservation/restoration, and wise management/use of natural resources. Planning and management of resources from loss/waste/harm in order to achieve continuous use/ Sustainable quality of living for mankind OR Conservation is the wise/judicious/intelligent use of our natural resources to ensure their availability, and preserve the quality of the environment.

(ii) Endangered species:Are organisms that have become depleted/rare. Due to human activity/natural disaster/epidemic. Those habitats have become so disturbed. That they may be lost forever/become extinct.

(b)(i)Necessity to conserve forests: Economic importance:

Forests produce timber for the construction industry/buildings/furniture/boats/paper.

Domestic: Firewood for charcoal, medicines, gum/resins/rubber/tannins/chemicals/turpentine.

Biological importance: Provide food/ shelter for many animals, reduce wind erosion/desertification, serves as wind breaks/checking strong winds, cause precipitation of water from damp air/can increase amount of rainfall in an area, protect source of streams/rivers, help in maintaining CO\(_2\) / O\(_2\) balance in the atmosphere/the plants remove CO\(_2\) for photosynthesis/supply 0\(_2\) /purifies the atmosphere.

Educational: For ecological studies, to prevent certain species from getting extinct. Recreational/ Tourism: Serve as tourist attraction.

(ii) Methods for the conservation of forests:Regulations made to control excessive deforestation, only mature trees should be felled. Planting new forest trees/afforestation where they have been completely destroyed. Discouraging extensive use of natural forests as a source of timber since animals and some other plants are also destroyed/displaced. Replacing harvested/felled mature trees by seedlings in plantations! reforestation. Prevention of forest fires. Controlling plant diseases by using pesticides/chemicals to kill pests. Using trained forest rangers/guards to guard the forests against intruders/fight fires. Educating the local population on the dangers of deforestation/carrying out awareness campaigns against deforestation. Establishment of forest reserve.

(c)(i)Importance of decomposers in the ecosystem: They break down organic materials that are difficult for organisms to digest, they return organic matter to the environment in an inorganic form, so that they can be re-assimilated by plants/recycling nutrients.

(ii)Plant decomposers: Fungi, Rhizopus, Bacteria. Animal decomposers: Earthworms, Termites.

Correct Answer: A. Human sense of smell is easily fatigued