HIE - Population Basics Lesson

 

Population Basics

The population size of a species depends on the biotic and abiotic factors present in that ecosystem. Biotic factors include the amount of food that is available to that species and the number of organisms that use that species as food. For life to thrive, a specific amount of abiotic factors are necessary. For example, too little water may cause land plants or animals to become dehydrated. Too much water, however, may cause drowning.

A population grows when the number of births is greater than the number of deaths. It shrinks if deaths exceed births. For a population to grow, there must be ample resources and no major problems. A population can shrink either because of biotic or abiotic limits. An increase in predators, the emergence of a new disease, or the loss of habitat are just three possible problems that will decrease a population. A population may also shrink if it grows too large for the resources required to support it.

When the number of births equals the number of deaths, the population is at its carrying capacity for that habitat. In a population at its carrying capacity, there are as many organisms of that species as the habitat can support. The carrying capacity depends on biotic and abiotic factors. If these factors improve, the carrying capacity increases. If the factors become less plentiful, the carrying capacity drops. If resources are being used faster than they are being replenished, then the species has exceeded its carrying capacity. If this occurs, the population will then decrease in size.

Every stable population has one or more factors that limit its growth. A limiting factor determines the carrying capacity for a species. A limiting factor can be any biotic or abiotic factor: a nutrient, space, and water availability are examples. The size of a population is tied to its limiting factor. If the limiting factor decreases, the population decreases. If the limiting factor increases, the population increases. If a limiting factor increases a lot, another factor will most likely become the new limiting factor.

Test your knowledge of limiting and not limiting factors using the activity below:

This page is developed based on this   https://en.wikibooks.org/wiki/High_School_Earth_Science/Human_Populations

 

 

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