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Year 8

Although animals do compete with each in an ecosystem, some actually work together.

There are 3 main types of relationships between organisms in an ecosystem.

Mutualism, Commensalism and Parasitism


Lets start with mutualism. Essentially this relationship means both parties benefit.

You scratch my back and I’ll scratch yours.

A Bee flies from flower to flower gathering nectar. When they land on a flower, the bees get some pollen on themselves. When they land on the another flower, some of the pollen from the first one flower rubs off, pollinating the plant.

Commensalism is a relationship where one organism benefits but the other is neither harmed nor benefits.

The pearl fish and sea cucumber have a very strange relationship. The pearl fish will live in the anus of the sea cucumber during the day and come out at night to feed.

The pearl fish gets shelter and a free ride, while the sea cucumber gets no benefit or damage.

Parasitism is where one organism benefits while the other is harmed.

Parasites live on their host, and either don’t kill the host or very slowly do.

If the parasite does eventually kill the host, they have to reproduce and disperse quickly, often through another organism. I.e. through infected blood by a mosquito.

The most obvious parasitic relationship is tapeworms and their host.

A tapeworm lives inside another animal, attaching itself to the host’s gut and absorbing its food.

The host loses nutrition, and may develop weight loss, diarrhoea and vomiting.

Parasites do not usually kill the host, as this would cut off their food supply.

Back in the day, tape worms were used to diet and loose weight.

Click here for a quick test on Competition and Relationships