Population InteractionsThis is a featured page


Food chain: a series of linkages showing one feeding relationship through the trophic levels in a population
1. Grasses --> Cottontail Rabbit --> Red Fox --> Grizzly Bear
2. Phytoplankton --> Antarctic Krill --> Mackerel --> Great White Shark
3. Grasses --> Desert Locust --> Fennec Fox --> African Lion

5.1.5 & 5.1.8
Food web: the sequences of many feeding relationships of the different organisms in an ecosystem, many food chains linked together

Food Web
For more information on Food chains/webs click here.

Different interactions/relationships between organisms:
Competition- challenging each other for the same resources
~Humans vs. humans for food, resources, shelter, etc
~Rabbits vs. cows for grass as food
Herbivory- animals eating plants
~Rabbits eating grass
~Cows eating grass
Predation- animals eating other animals
~Humans eating cows
~Owl eating mouse
Parasitism- Parasite and host, where the parasite benefits, and the host is harmed
Mutualism- where both organisms benefit, a win-win situation
~clownfish/sea anemone
~humming bird drinking pollen\

This video is worth watching. It's a great song explaining the interactions between species of a population. If the video doesn't work on this page click here.

Competitive Exclusion: Two species competing for the same limiting resources cannot coexist in the same place. One species will eather leave or become extinct.

Fundamental Niche: Where the species is designed to live the best.
Realized Niche: Where the specices actually resides because of competition.

Generally, populations follow an s-curve as they grow.
Figure 1
Different density dependent factors (competition for resources, build-up of toxins in metabolism, disease, predation) determine how limited resources are.
When these factors lead to higher mortality rates, the population decreases. However, this decrease in population leads to more available resources, thus allowing the population to rebound, which leads to less resources, and so on. The population is left in a state of perpetual increase and decrease.
In order to insure the survival of offspring, populations tend to produce more offspring than the environment can support. This makes it certain that, even if some offspring die, as many offspring that resources and other environmental factors allow to survive, will survive, thus continuing the growth of the species.
Click here for more information on carrying capacity.

As a tool for natural selection, an organisms ability to adapt is a key factor in determining how it evolves. The changing environment of a population is what allows for natural selection to occur. The more an organisms adapts to changing population factors, such as competition, disease, and predation, the greater it's ability to survive becomes. For example, as time passes, mutation occurs, and a bird is born with a longer beak than other birds. It is then able to easier reach it's food, and is able to out-compete other birds with shorter beaks. Thus, the bird with the longer beak is able to reproduce more plentifully and it's offspring will be able to do so as well, until the new species of bird out-competes the other birds into extinction.

Latest page update: made by arkwrightmd , Oct 24 2009, 11:55 AM EDT (about this update About This Update arkwrightmd Edited by arkwrightmd

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