(a) Explain the term adaptation in relation to the mode of life of an organism. (b) Explain how each of the following structures adapt the organisms that po...

(a) Adaptation

Adaptation is the possession of special structural, physiological or behavioural features that enable an organism to survive, feed, escape enemies and reproduce successfully in its particular habitat or mode of life.

(b) How each structure adapts the organism to its mode of life

• (i) Succulent leaves in Aloe sp. - The thick, fleshy leaves store large amounts of water, enabling the plant to survive in dry (xerophytic) habitats where water is scarce.
• (ii) Succulent stems and reduced leaves in cactus plants - The swollen green stem stores water and also carries out photosynthesis, while the leaves are reduced to spines to cut down water loss by transpiration and to protect the plant from being eaten. This adapts the cactus to survive in deserts.
• (iii) Short, strong beaks in fowls - The short, hard, pointed beak is suited for pecking and picking up grains and seeds and for scratching, adapting the fowl to a grain-feeding (graminivorous) habit.
• (iv) Counter shading in fish - The dark upper (dorsal) surface and light lower (ventral) surface act as camouflage: viewed from above the fish blends with the dark water below, and from below it blends with the bright surface, helping it to escape predators and to approach prey.
• (v) Tiny scale leaves on needle-like branches of pine trees - The very small, needle-like leaves greatly reduce the surface area exposed, cutting down water loss by transpiration and enabling the pine to survive in cold or dry conditions.

(c)(i) Population

A population is the total number of organisms of the same species living together in a given area at a particular time.

(c)(ii) Five effects of overpopulation on a community

• Increased competition for food, water, space, light and other resources.
• Shortage of food leading to famine, malnutrition and starvation.
• Rapid spread of diseases and epidemics due to overcrowding.
• Depletion or exhaustion of natural resources and increased environmental pollution.
• Higher death rate, unemployment, poor sanitation and pressure on social amenities (housing, schools, hospitals).