Explain how each of the following may affect population growth of the organisms in a habitat.

a)Parasitism.
-Parasites may kill the host; deprive the host of food/ make it weak/ sick; reducing the reproductive ability; and make the host susceptible to predation;
b)Competition.
-Organisms compete for food, light, water, mates and shelter; leading to death; and migration of weak organisms; the population of strong species increases;
c)Human activities.
-Pesticides/ agrochemicals introduced by man reduce the population of organisms in a habitat; deforestation destroys plants and forests; organisms die/ migrate; construction of physical amenities/ mining destroys habitats for organisms; causing organisms to migrate/ die; killing of animals through poaching/ hunting/ fishing reduces the population; environmental conservation; population control methods/ family planning / selective breeding may decrease the population;
d)Food
-More food causes population increase; due to increase in the rate of reproduction; and immigration/ migration into the ecosystem; this leads to competition for food; which will cause death/ emigration/ migration out thus reducing population;