(a)(i) Population: This is a group of individuals; of the same species; inhabiting a particular area/habitat; at a particular point in time.
(ii) Competition: - This is the interaction between members of the same population/ species/intra - specific/two or more populations/species/inter - specific; occupying the same trophic level; to obtain mutually needed resources; that are short in supply in their environment.
(iii) Succession: - This is the step by step/orderly; and gradual replacement of communities; arising from a change in the environment/environmental factors; which leads to a climax/stable community.
(b) (i) Sources of noise pollution: -

Electronic sound system
Sirens
Generators
Airplanes
Factory machines
Industrial machines
Canons shots/guns firing
Artillery firing
Quarry activity/construction site
Motor vehicles.

(ii) Prevention:

Legislation
Education/public enlightenment
Siting factories, industries, military site away from residential areas
Use of sound proof/silent generators.

(c)(i) Effects of smoke on humans: -

Causes breathing difficulties.
Causes injury to the lining of respiratory tracts/ lungs.
Reduces visibility; reduces photosynthesis leading to lower crop yield.
Causes discomfort to the eyes.
Contains carbon monoxide which is injurious to man.

(ii) Effects of sewage on human:

Untreated sewage discharged into water bodies makes water unfit for drinking/swimming
may cause spread of water borne diseases/correctly named borne disease.
its toxic to aquatic organisms thereby depleting food source for man.
makes water unsafe for domestic use.
leads to offensive odour.
poisonous substances may enter the food chain which is unsafe for man.