And the Interactions in Ecosystems

The resources in the environment will not be able to support an infinite increase in the population of a species. Eventually the # of births will equal the number of deaths as resources become relatively scarce. This will mean the population is at equilibrium.

When the population hits the maximum number of individuals an ecosystem can support without reducing its ability to support future generations of the same species, it is said to be at its carrying capacity

One of the things that determines the carrying capacity of a population is called a limiting factor. Usually if the limiting factor is eliminated the carrying capacity will increase. The limiting factor is an environmental factor that prevents an increase in the number of organisms of a population or prevents them from expanding into new habitats.

Abiotic limiting factors include sunlight, water, soil, fires, droughts etc. Biotic limiting factors include competition for resources, predation, disease etc.

Competition is the interaction between 2 or more organisms for the same resource in a given habitat. There can be intraspecific competition (2 animals of the same species) as well as interspecific competition (different species)

For 2 species to coexist in an area they must have slightly different niches. Often competition for resources will cause species to specialize on certain aspects of their potential niche.

Predation occurs when an organism eats another organism to obtain food. Prey organisms will adapt to the predators that hunt them so that they are faster, stronger or more aware of their surroundings.

Some other animals use mimicry to avoid being eaten. The monarch butterfly and the viceroy butterfly both taste terrible and they look very similar. This makes it easy for predators to recognize and stay away from them.

There are a couple snakes in Ontario that mimic the rattlesnake to avoid predation. The fox snake does not look too much like a rattlesnake but when upset it will shake its tail back and forth in the dead leaves on the forest floor which makes a rattling sound.

Example of how predation affects populations

Symbiosis is the close interaction between species where one species lives in, on or near members of another species.

There are 3 types of symbiosis: 1. Mutualism – both species benefit

2. Commensalism – one species benefits while the other is unaffected.

3. Parasitism – one species benefits at the expense of another species.

Answer questions 1-3 pg 42