COMMUNITY INTERACTIONS

COMMUNITY INTERACTIONS
Competition
→Between members of the same species (1 species only)
Ex: Weeds racing to produce the most seeds, each seedling (new grown plant) striving to grow the tallest in order to get the most sun.
→ Between members of the different species (more than 1 species).
Ex: lion, tiger and hyena are fighting each other in order to get the same food.
Predation
In this relationship one organisms (the predator) captures and feeds on the other organisms (the prey)
Symbiosis
Symbiosis basically means ‘living together’ and it refers to a close relationship between two species. This is a relationship between individuals of two or more different species which live closely together. They are divided into:
a) Mutualism
→both species benefit from the relationship.
Mutualism is an interaction between organisms of two different species in which each member benefits.
Ex: A clown fish clean the anemone from its parasites by eating it while the anemone protects it against its prey. Anemones also receive food drawn by the clownfish.





















































The drawing shows the Nile crocodile opening its mouth to permit the Egyptian plover (name of bird) to feed on any leeches attached to its gums.


The relationship between most mycorrhizae and certain plants. Mycorrhizae are fungal growths on the roots of such plants as heaths, orchids, and many conifers. The fungi penetrate the roots of the plants and make soil nitrogen available to the plants, receiving carbohydrates in return

Symbiotic nitrogen-fixing bacteria, present in small nodules on the roots of beans like the picture beside. In return for sugars from the plant, fix nitrogen which can be used by the plant for growth. The most important belong to the genus Rhizobium, which infects the roots of both trees and herbaceous plants in the bean family (Leguminosae).

b) Parasitism
→one species benefit, the other disadvantage.
: One organism lives on or inside another organism and harms it.
Ex: A flea/lice feeds on the blood of its host (ex: dog, human).
Mistletoe Plant Growing in a Tree
Mistletoe is a widespread flowering plant parasite that grows on oak, apple, juniper, pine, and other trees. Most mistletoe species are partial parasites. Their leaves, found on the surface of branches and trunks, produce sugar through photosynthesis, but their roots penetrate into the tree’s tissue and absorb its nutrients.

c) Commensalism
→one species benefit, the other is unaffected (no benefit and no disadvantage).

Ex: The orchid benefit because it can absorbs water and minerals from rain water by perching in the tree. But the tree is not affected.
Remoras that ride attached to sharks and other fishes. Both remoras feed on the leftovers of their hosts' meals.


There are certain species of Goby, like Astropyga radiate, that live between the spines of toxic sea-urchins. The Goby get protection from the sea-urchin (host) while their host is not get benefit and get no disadvantaged by this relationship.

In Papua New Guinea there are several interesting commensalistic relationships. Imperial shrimps, Periclimenes imperator, hitching a ride on the large sea cucumbers found here, (genera Stichopus). The shrimps get transported through a large area of potential food by their host (so they can save energy). They can be observed getting off their host cucumber to feed in productive areas, and back on for a ride to the next spot!

Epiphytes are plants that live perched on sturdier plants. They do not take any nourishment from their host and simply benefit from being better exposed to sunlight. Some examples: many orchids

Barnacles are sedentary, highly modified crustaceans resembling conical pyramids. Barnacles live by using long, feathering appendages to sweep the surrounding water for small, free-floating organisms. The critical resource for barnacles is a place to stay. Barnacles attach to rocks, ships, shells, whales, and just about anywhere else they can gain a foothold. The example barnacles are attached to the shell of a scallop. The barnacle gains a place to live and, the scallop is not harmed by the presence of the barnacles. Therefore the relationship is commensalism

Neutralism
In this relationship none of the organisms involved get the benefit or the disadvantage.
Ex: the relationship between the bee and the eagle.