Intraspecific competition occurs when individuals of the same species compete for resources such as food, water, breeding sites, light, space, or shelter.

1. Resources are plentiful, all organisms have enough to survive and reproduce - population size increases
2. Resources become more scarce and are shared between more individuals so some individuals die - population size decreases
3. There is less competition in the smaller population so more organisms survive and reproduce - population size increases

This principle states that where two species are competing for limited resources, the one that uses these resources most effectively will ultimately outcompete the other.

Interspecific competition occurs when individuals of different species compete for resources such as food, water, breeding sites, light, space, or shelter.

A predator-prey relationship is an interaction between two species where one species, the predator, hunts and kills the other, the prey.

1. Sudden bursts of speed
2. Stealth
3. Camouflage
4. Better means of detecting prey

1. Camouflage
2. Protective features like spines
3. Mimicry

Predator-prey relationships create a selection pressure.

Organisms that can escape predators effectively are more likely to survive and reproduce, leading to evolution.

1. Increase in prey population size provides more food for predators
2. Increase in predator population size means more prey are consumed and their death rate exceeds birth rate
3. Decrease in prey population size increases competition among predators for food
4. Decrease in predator population size means less prey are killed and prey population size increases again