個体数の増加

Population growth is an increase in the number of individuals in a population, and many factors can limit this growth.

For example, the size of a puffer fish population changes over time. Individuals move into an area through immigration and leave through emigration. The population also changes when new fish are born, and others die.

If resources are unlimited, a population can grow exponentially over time, producing a J-shaped curve. But in nature, populations face environmental limits on growth. These limits define the habitat’s carrying capacity, or the maximum number of individuals the environment can support.

As the puffer fish population uses more food and space in the habitat, competition between individuals increases because they share the same limited resources. Other factors, such as predation, disease, and environmental conditions, also contribute to limiting population size. As a result, the population approaches carrying capacity, growth slows, and follows a more realistic logistic growth pattern, producing an S-shaped curve.