Population Ecology


Population Growth- an increase in the size of a population over time
  • Factors that affect population growth include the number of births, number of deaths, and the number of individuals that enter or leave.
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Exponential Growth- as a population gets larger, it also grows faster

This is an example of positive feedback. The more
individuals there are in a population the faster they will
breed. The growth curve looks like this
(often called the J-curve).



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Limiting Factors- cause a population to stop increasing
- Density dependent factors have an increasing effect as the population increases.
  • Disease
  • Competition for resources- food, water, mates, territories, nesting sites
  • Predation
  • Stress

-Density independent factors afForest_Fires.jpgfect all populations regardless of dflood.jpgensity.
  • Temperature
  • Storms
  • Floods
  • Droughts






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Carrying Capacity
The effects of Limiting Factors result in
carrying capacity- the number of individuals
in the population that an environment
can support.



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Growth Curve Patterns:
J-Curve- organisms in unstable environments
*Small body size
*Reproduce rapidly
*Short life span
*For example: bacteria, insects




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S-Curve- organisms in stable environments
*Larger body size
*Reproduce slower
*Longer life span
*Mature slower, live longer
*For example: elephants, trees, humans

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Competition- a contest between individuals, animals, groups, ect. for territory, a niche, or a location of
resources. Animals compete over water supplies, food, mates,
and other biological resources. Humans compete for water,
food, and mates, though when these needs are met deep rivalries
arise over the pursuit of wealth, prestige, and fame.

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Predation- a biological interaction where a predator (an organism that is hunting) feeds on its
prey (the organism that is attacked). Predators may increase the biodiversity of communities by
preventing a single species from becoming dominant.


Biodiversity- the degree of variation of life forms within a given ecosystem,
biome, or an entire planet. Biodiversity is a measure of the health of ecosystems.
Biodiversity impacts human health in a number of ways, both positive and negative.
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Bioaccumulation refers to the accumulation of
substances, such as pesticides, or other organic
chemicals in an organism. Bioaccumulation occurs
when an organism absorbs a toxic substance at a
rate greater than that at which the substance is lost.






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Organism- any contiguous living system (such as animal, fungus, micro-organism, or plant). All
organisms are capable of response to stimuli, reproduction, growth and
development, and maintenance of homoeostasis as a stable whole.




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Species- one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. Species that are believed to have the same ancestors are grouped together, and this group is called a genus. A species can only belong to the genus that it was grouped into.