The negative interaction that occurs among organisms whenever two or more organisms require the same limited resource is known as competition. All organisms need resources to grow, reproduce and persist. For example, animals need food and water, whereas plants need soil nutrients (for example, nitrogen), light, and water. Organisms, however, cannot receive a resource when other organisms consume or defend that resource. Therefore, in this type of interaction both the organisms gets harmed.

Any morphological, psychological, behavioural attribute enabling an organism to survive and reproduce in its habitat is called adaptations, and it allows the organisms to live in various habitats. They originate due to the natural selection of proper variations appearing in living beings through mutations and recombination.

Mortality or death rate is an expression of death or loss of individuals in a population during a given time period. The rate of mortality may be expressed as the percentage of dying individuals within a particular time. Mortality and emigration together decrease population density and birth rate and immigration increases population density.