Why do populations tend not to continue to increase exponentially in an environment? thanks!?

Question

Why do populations tend not to continue to increase exponentially in an environment? thanks!?

Answer 1

This applies to all populations: not just human. Basically there are two types of reason:

First: some resource starts to run out. It might be food, space, light, anything that the members need and is in limited supply.

Second: they start to change their environment so that it becomes unfavorable, such as accumulated wastes

Answer 2

The population starts to come up against limits to their growth.  Food becomes scarce, or they stop having kids because they want their space or they see other people with kids and their cuteness is seriously offset by the fact that children are screaming maniacs and walking advertisements for birth control.  You end up riding a crowded bus and looking at a fat woman's butt and it is not a turn on.

In China it may be because the only thing most families want is a boy.  The inevitable result will be a lot of horny single men in the future with no one but each other as love objects.

Answer 3

a) Some resource in their environment limits the population.  The maximum population possible is called "the carrying capacity of the environment" for that population.

For example:  phytoplankton need iron, phosphorus, and fixed nitrogen.  In most of the ocean, those are in limited supply.  With fertilizer from farm run-off flowing from rivers into the ocean, some places experience an "algal bloom."

b) Predation or competition

The presence of predators can keep a prey population from burgeoning.  Cougars eat deer -- enough so that the population of deer cannot increase indefinitely.

Cougars also compete with each other for hunting grounds.  The population of cougars can't increase indefinitely because adult cougars will chase other adult cougars off their hunting territory, and there's a limited amount of good hunting territory.