What causes the "struggle for existence" according to natural selection?

The concept of the "struggle for existence" in natural selection is fundamentally linked to both limited resources and the overproduction of individuals.

Limited resources refer to the finite availability of necessities such as food, water, shelter, and mates, which means that not all individuals in a population can survive and reproduce. This scarcity creates competition among individuals for those limited resources.

Overproduction of individuals, on the other hand, is a characteristic of many species; they tend to produce more offspring than can realistically survive to maturity. This leads to a situation where, although many individuals are born, the limited availability of resources means that only a fraction will succeed in surviving and reproducing.

By combining these two aspects—resource limitations and overproduction—you can see how they work together to create a scenario where individuals must compete for survival. This struggle drives the process of natural selection, as individuals that are better adapted to their environments are more likely to survive and pass on their traits to subsequent generations. Thus, recognizing both factors together provides a more comprehensive understanding of the dynamics at play in natural selection.