Author: Laura Dewis

Working Together - Co-operation and mutualism

Updated Monday, 7th March 2005
In an unpredictable environment, populated by predators, parasites and competitors, it often pays to co-operate

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bluebells

When both partners benefit we call the relationship mutualism. Co-operating allows organisms to increase the number of young they produce, and even to survive in unfavourable conditions.

Who co-operates?

Co-operation can be seen in many animals, birds, and fish. Many birds, fish and grazing animals form groups as a defence against predators. During the summer, female bats live in maternity roosts where they rear their young together. This allows individual females to leave their young in the relative safety of the group whilst they go and hunt insects. Co-operation in social insects such as ants allows them to build large nest structures and to share tasks, such as defence and foraging, efficiently.

Mutualistic relationships also exist between very different species. As anyone who picks blackberries in autumn will know, many plants produce seed-containing fruits that are attractive to animals. Birds and mammals eat the fruit and transport the seeds to new habitats in their droppings. This is not a free ride for the plant, it has to use energy to produce attractive fruits and seeds with a hard coating, which prevent them being digested. However, the benefit of being able to colonise new places is worth this extra effort.

Many flowering plants have evolved relationships with pollinators, who spread pollen between plants. The flowers offer nectar, a sugary liquid, and sacrifice some pollen as food to attract pollinators. The pollinators in return are dusted with pollen, which they carry between flowers. This allows pollen from one plants to be transferred to another individual and is known as cross-pollination or outbreeding.

Animal pollinators and plants have co-evolved, with plants producing flowers optimised to attract pollinators, and pollinators developing mouthparts optimised to extract nectar from flowers. Whilst many plants are pollinated by a variety of animal species, some have very close relationships with specific animal pollinators.

Close associations

When the relationship between two co-operating species becomes so intertwined that they become dependent upon one another for survival it is usually known as symbiosis. Living together has allowed some species to survive in the most inhospitable habitats. The barren face of a rock provides little in the way of shelter or nutrients, but lichens often thrive on them. Although we identify individual lichens as ‘species’ they are made up two species - an alga, which can photosynthesise and accumulate sugars, and a fungus that provides the structure of the partnership and stores water.

Next: Studying communities

 

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