Outcomes of Competition Niches of similar species may overlap. Two

species cannot compete for the same limiting resource for long.

eventually one species outcompetes the other

One species survive, other emigrates OR dies out

Even a minute reproductive advantage leads to the replacement of one species by the other.

This is called the COMPETITIVE EXCLUSION PRINCIPAL.

Evidence for Competitive

Exclusion the Russian ecologist, G.F. Gausse demonstrated that Paramecium aurellia outcompetes and displaces Paramecium caudatum in mixed laboratory cultures, apparently confirming the principle.

Resource Partitioning

When two or more similar species coexist, such as

these varieties of warbler, each species only uses

part of the available resources. This is called resource partitioning.

(species sharing resources)

PARASITISM Parasitism is a species interaction that

resembles predation in that one individual is harmed while the other benefits.

However, in parasitism, the parasite feeds on the host individual.

This does not result in the immediate death of the host. Rather, the parasite may feed on the host for a long time instead of killing it.

Ectoparasites

Ectoparasites are external parasites.

They live on their hosts body, but do not enter it.

Examples include ticks, fleas, lice, lampreys, leeches and mosquitoes

Endoparasites

Endoparasites are internal parasites, and live inside the host’s body

Endoparasites include bacteria and other micro-organisms, and many worms

Resource partitioning amongst plantsDifferent species of plants in the same habitat will compete for the same resources like light, water, mineral salts, etc. Different species of plants grow to different heights or have roots that are different lengths so they divide the resources, accessing them in slightly different ways

Resource partitioning: co-existing shore birds

Human influence on community structure

The elephant herd in the Kruger National Park increased from 8, 000 to 12,500 in 2008 and to 19 000 in 2009. The elephant population is increasing by 7% per year, and might reach 20 000 by 2012. This large herd cannot be sustained since adult elephants consume 130 kg food a day and they live for 55 – 65 years. On 25 February 2008 the SA Government finally concluded it would have to lift a 17 year-old moratorium on the culling of the native elephant to cope with its booming population. Minister van Schalkwyk announced that killing of excess animals would only be allowed once all other options (translocation and contraception) had been ruled out. Minister van Schalkwyk said:”Our simple reality is that elephant population density has risen so mulch in some southern African countries that there is concern about impacts on the landscape, the viability of other species and the livelihoods and safety of people living within elephant ranges.”

Mutualism Mutualism is a symbiotic relationship in which

both members of the association benefit. Often help organisms obtain food or avoid

predation. Bacteria in human intestinal tact.

Need not be equally beneficial to both species. Cleaning Symbiosis

Pollination

Pollination is the most important of the mutualistic relationships.

The plant provides food for the pollinators, which in turn carries the pollen to another flower

COMMENSALISM

Is a relationship in which one species benefits and the other is not affected