Beneficial Interactions

Classification of interactions:

There are a large number of ways that organisms can interact.

classification of these interaction makes studying them easier.

two types of interactions.

1. detrimental -- when one or more organisms are harmed or disadvantaged from the relationship.

2. beneficial (symbionic): when one or more organism benefit from the relationship.

Predator Prey Relationship:

is a detrimental feeding relationship where the predator (consumer) obtain its food by killing an organism for example spiders eating flies or eagles eating bush rates.

predators affect the abundance of their prey.

as prey are consumed, their numbers decline, leading to a shortage of food for the predators whose numbers also decline.

Factors affecting predator-prey populations:

number of predators competing for same prey.

avaliability of preys food.

birth rate.

death rate.

number of males and females.

size of ecosystem for supporting the predator and prey numbers.

Allelopathy:
allellopathy is a plant relationship.
a plant produces chemicals that can be beneficial or detrimental to another plant.
many australian plants produce allelochemicals. these substances are released by the plants and concerntrate in the soil.
they inhibit the growth of other plants in the area and give the plant a competitive advantage.
soem pine trees are allelopathic. when their needles fall to the ground, they begin to decompose and release acid into the soil. this acid in the soil keeps unwanted plants from growing near the pine tree.
fern frons produce chemicals that prevent pine seeds from germinating. allelopathy can be used in agriculture as natural form of weed control.

symbiosis is the term used for interactions in which two organisms live together in a close relationship that is beneficial to at least one of them.
there are there types of beneficial or symbiotic interactions.
parasitism- one species benefit and the other is harmed.
mutualism- both species in the relationship benefit from the association.
commensalism: one species benefit and the other is unaffected.

parasitism:
parasitism is the close relation between two organisms where one is benefited and the other is disadvantaged.
the organism benefiting lives on or within the body of the disadvantaged organism (called the host). although the host is harmed, it is not usually killed by the parasite. the parasite is often smaller than their host and they may live on the surface of their host (endoparasites e.g: ticks, fleas and tinea) or internally (endoparasites e.g tapeworms).
other examples include disease-causing organisms like bacteria and viruses.
plant parasites are strangler fig and mistletoe.

mutualism:
mutualism is the relationship between two organisms where both organisms benefit from the relationship. neither can live without the other. a common example of mutualism is lichen.
lichen is a close relationship between a fungus and algae.
lichen is a close relationship between a fungus and algae. the fungus gains nourishment from the photoshynthetic algae. the algae are provided with a substrate to live within. lichen is found growing on rocks, trees and buildings.
-reef-builing corals have symbiotic algae within their tissues which provide the yellow-brown pigment that give the coral its colour.
-the algae live, reproduce and photosynthesise int he host and use the waste products of the heat.
-in turn, the coral uses oxygen and food produced by the algae during photosynthesis to grow, reproduce, and form its hard skeleton, which is the basis of the reef.
the formation of the great barrier reed depends n this mutualistic relationship.

commenalism:
commenalism is a loose relationship where neither organism is disadvantaged but one maybe advantaged. an example of commenalism is a remora attached to a shark. a remora is a small fish with suckers (modified dorsal fins) on its head.
it attaches to the shark and is carried around by the shark. the remora can feed on any scraps of food that the shark misses.
the shark does not seem to be affected by this
the bird nesting in a tree is another example of commensalism.
the bird gains a place to raise it's young and the tree is not affected.
lichen growing on a tree trunk show a common from of commensalism. the lichen gets a place to attach off the ground and the tree is not affected by the lichen.

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