Free WAEC Biology Theory Past Questions

(i) Name the biological cycle

Answer: Water cycle

(ii) Explain briefly three roles played by plants and animals in the cycle.

Answer:

– Plants absorb water from the soil. The water moves from the roots through the stems to the leaves. Once water reaches the leaves, some of it evaporates from the leaves, adding to the amount of water vapor in the air. This process of evaporation through plant leaves is called transpiration.

– Water cycle is a product of respiration in plants. Water is carried from the roots of the plant throughout the plant to the underside of the leaves where it evaporates off into the atmosphere.

– Animals release water vapor into the water cycle when they exhale

– Animals contribute to the water cycle mainly through breathing, perspiration, and excretion of waste.

(iii) Name the processes that occur in X, Y and Z.

Answer:

– X represents condensation
– Y represents transpiration/respiration
– Z represents evaporation

c. Complete the table below.

Answer:

d. (i) What is decay of organic matter?

Answer:

Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts.

(ii) Name two groups of organisms that cause decay of organic matter.

Answer:

Most decomposers are microscopic organisms, including protozoa and bacteria.

Other decomposers are big enough to see without a microscope. They include fungi along with invertebrate organisms sometimes called detritivores, which include earthworms, termites, and millipedes.

(iii) State one other factor that causes decay.

Answer:

– Temperature
– Oxygen (aeration)

(iv) Name the biological cycle that involves decay.

Answer: Nitrogen cycle

e. Explain briefly the mode of nutrition in carnivorous plants.

Answer:

These are plants that obtain energy by feeding on small insects. They have developed special structures to trap their prey. Examples of insectivorous plants are pitcher plants, venus flytraps, and sundew.

In the pitcher plant, some of its leaves are modified to form a pitcher, like a container; a deep cavity filled with digestive liquid. The inner walls of the containers are slippery and smooth. Once insects are trapped, they are unable to come out.

At the bottom, they are digested by a pool of liquid containing digestive enzymes.