Intraspecific Competition

Intraspecific competition is competition between individuals of the same species. It is usually the most intense form of competition, because members of the same species have exactly the same needs: the same food, the same nest sites and the same mates.Its effect on population size follows a pattern:
1. When a population is small, resources are plentiful, so most individuals survive and breed and the population grows.
2. As the population grows, each individual gets fewer resources.
3. Some individuals fail to get enough, so the death rate rises and the birth rate falls.
4. Population growth slows and the population levels off, then fluctuates around the carrying capacity.
5. If the population falls, competition eases and numbers rise again.So intraspecific competition is a density-dependent factor that regulates population size by negative feedback.Examples: robins defend feeding territories in winter, and birds without a territory are less likely to survive or breed. In a dense stand of tree seedlings, the tallest plants shade the others, which die, so the number of plants falls as they grow. This is called self-thinning.Intraspecific competition is also a driving force of natural selection. Individuals with alleles that make them better competitors, for example at finding food or attracting mates, are more likely to survive and reproduce, and so pass those alleles on to the next generation.