Species Interaction

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Species Interaction

* The relationships between two species in an ecosystem.
* The interactions between two species need not be through direct contact. Species may affect each other through intermediaries such as shared resources or common enemies.

Major factors in evolution and adaptation:
* Predation
* Competition for scarce resources

Terminologies:
* Habitat – the actual physical location where a species lives. * Conditions – physical or chemical attributes of the environment. * Resources – substances that can be consumed by an organism.

ECOLOGICAL NICHE

* Describes how an organism or population responds to the distribution of resources and competitors and how it in turn alters those same factors. * Consists of all the factors necessary for its existence – approximately when, where, and how a species makes its living.

a. Fundamental Niche – the full potential range of conditions and resources it could theoretically use if there were no competition from other species. Niches of a species overlap with those of other species. b. Realized Niche – is where the species does live, because of the factors mentioned above have forced it to retreat from parts of the fundamental niche.

Categories of Species Interactions:

1) COMPETITION
Competition is an interaction between organisms or species, in which the fitness of one is lowered by the presence of another. Limited supply of at least one resource (such as food, water, and territory) used by both is required.

* “Survival of the fittest” by Herbert Spencer (who coined the term) and Charles Darwin

Types of Competition by Mechanism:
a. Interference competition – occurs directly between individuals via aggression. b. Exploitation competition – occurs indirectly through common limiting resources which act as an intermediate. c. Apparent competition – occurs indirectly between two species which are both preyed upon by the same predator.

Types of Competition by species
a. Intraspecific competition – occurs when members of the same species vie for the same resources in an ecosystem. * Ex. 2 trees growing close together will compete for light, water, and nutrients b. Interspecific competition – may occur when individuals of two separate species share limiting resources in the same areas. * Ex. Cheetahs and lions both feed on similar prey

2) PREDATION
Predation describes a biological interaction where a predator (an organism that is hunting) feeds on its prey (the organism that is attacked). The act of predation always results in the death of its prey and the eventual absorption of the prey’s tissue through consumption.

The unifying theme in all classifications of predation is the predator reduces its prey’s chances of survival, reproduction, or both.

Functional Classification: (by the way in which they eat)
a. True predation – a true predator is one which kills and eats another organism. * Ex. Snake swallowing a frog, baleen whales eating millions of microscopic planktons, Jaguars, Lions, Tigers, etc. b. Grazing – an herbivore feeds on plants, and also on other multicellular autotrophs. Only eat a small part of the plant, allowing it to regrow once again. * Ex. Grazing livestock – grass, female mosquitoes – hosts, starfish(grazed on) c. Parasitism – form very close associations with their hosts, usually having only one or at most a few in their lifetime. Significantly reducing the fitness of their host. * Ex. Macroscopic mistletoe, microscopic internal parasites such as cholera d. Parasitoidism – living in or on their host and feeding directly upon it, eventually leading to its death. * Ex. Ichneumon wasps – laying eggs in a caterpillar. Its larva(e) feed on the growing host, soon devouring the internal organs until finally destroying the nervous system resulting in prey death; other ex. moths, butterflies, ants, flies

Four stages of...
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