Organisms that show r -strategy are relatively small organisms with short life spans and often live in unstable environment. Their survival depends on their ability to produce large number of offspring rather than on their ability to compete. They are able to colonise a habitat rapidly, utilising food and other resources before other organisms gets established. For example, bacteria, insects, etc. Human, rhinoceros and whale are k -strategists. They are highly adapted to their (stable) environment and able to compete successfully for food and other resources. They have low rate of reproduction and have relatively long life spans.