## Density-dependent factors limit population growth

Why did the lionfish population’s growth rate decrease as the population grew very large? Populations of lionfish, and other species with logistic growth, are limited by negative density-dependent factors. These factors reduce a population’s growth rate when the population’s density (and thus size) is large — typically by reducing the survival, reproduction, or growth of the individuals in the population.

**
Read about four negative density-dependent factors to learn how
they limit population growth.
**

### Intraspecific Competition

**Intraspecific competition** is competition
between individuals of the same species for food, space, and
other resources. As the population grows and consumes more
resources, individuals must compete for the remaining, limited
resources. This reduces the survival, development, and
reproduction of some individuals — which ultimately reduces
population growth.

### Interspecific Predation

**Interspecific predation** is when individuals
in a population are killed and eaten by predators of a
different species. As a population grows, individuals in the
population are more likely to be found and killed by
predators. This reduces individual survival and overall
population growth.

### Diseases and Parasites

**Diseases and parasites ** become more common as
a population grows larger. They can kill some individuals and
lower the fitness (reproduction, likelihood of survival, or
lifespan) of others, which reduces overall population growth.

### Case Studies

**
Explore case studies from published research that show different
negative density-dependent factors at work.
**
You may explore all the case studies on your own or explore one or a
few in-depth and learn from classmates about the other cases.