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Population limits and species interactions

Population growth – what is it?

Reproductive potential – is a population’s maximum size, if all of the species found mates and had offspring, and none of the offspring get eaten, die from disease, or run out of resources. This is how big the population would get if it had no limitations.  In real life this doesn’t occur – there are always limiting factors.

Fish population growth

Changes in predator (wolf) and prey (moose) populations over a 40-year span.
notice how the size of one population affects the size of the other.

Image from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates and WH Freeman.

Wolf Moose predator prey graph

Carrying capacity, competition within a population,
http://www.nexuslearning.net/books/holt_env_science/8-1.pdf
Human population growth is not like that of most other animals. For a few thousand years it has shown exponential growth.  This growth obviously will not last forever.

“When resources are unlimited, a population can experience exponential growth, where its size increases at a greater and greater rate.

Source: Boundless. “Exponential Growth.” Boundless Biology. Boundless,  https://www.boundless.com/biology/textbooks/boundless-biology-textbook/population-and-community-ecology-45/environmental-limits-to-population-growth-251/exponential-growth-929-12185/

Human population growth
Eventually a population stops growing exponentially, because organisms die due o startvation, disease, bad weather, etc.

Image from http://andyarthur.org/topics/experiences/the-woods/carrying-capacity.html

Deercarrying_capacity_chart surplus decreased

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Websites with related notes

https://sites.google.com/a/ccsd.edu/lappi/home/biology/ecology

 

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