(a) List five morphological features that are characteristic of plant found in each of the following habitats:-(i) tropical rainforest. (ii) savanna. In eac...

(a) Morphological features of plants and their functions

(i) Tropical rainforest plants

• Broad leaves: increase surface area for trapping the limited light and for photosynthesis.
• Drip tips on leaves: allow excess rain water to run off quickly, keeping the leaf dry.
• Buttress and prop roots: give support to the tall trees in the shallow forest soil.
• Tall, straight trunks: raise the crown up to reach sunlight above the canopy.
• Climbing and epiphytic habit (lianes, climbers): enable weaker plants to reach light without building thick stems.

(ii) Savanna plants

• Small or needle-like/reduced leaves: reduce surface area and water loss by transpiration.
• Thick, corky (fire-resistant) bark: protects the plant against bush fires and heat.
• Deep and extensive root systems: reach water deep in the soil during the dry season.
• Thick waxy cuticle / hairy leaves: reduce transpiration.
• Water-storage tissue in stems (succulence): stores water for use in the dry season.

(b) Ecological succession is the gradual and orderly replacement of one community of organisms by another in the same area over a period of time, until a stable, self-maintaining community (the climax community) is reached.

(c) The carbon cycle (diagram only)

The diagram should show a closed loop with labelled arrows illustrating:

• Photosynthesis: green plants take in carbon dioxide from the air and fix it into organic food.
• Feeding: animals obtain carbon compounds by eating plants (and other animals).
• Respiration: plants and animals release carbon dioxide back to the air.
• Decomposition: decomposers (bacteria and fungi) break down dead plants and animals, releasing carbon dioxide.
• Combustion: burning of wood and fossil fuels (coal, oil) returns carbon dioxide to the atmosphere.

Its importance: it keeps the amount of carbon dioxide in the atmosphere fairly constant, supplies the carbon needed to build all organic molecules (the basis of all life), and links producers, consumers and decomposers.