SYMBIOSIS Populations & Ecosystems 2011

Symbiosis= relationship where two different organisms live together in close contact Obligatory symbiosis: where symbiosis is essential for life. Facultative symbiosis: symbiosis is beneficial but not essential. Commensalism One species benefits while the other neither benefits nor is harmed. Mutualism Both participating species benefit. Parasitism One species benefits but the other is harmed.

Task: Working in pairs, read the given example and decide whether commensalism, mutualism or parasitism is occurring, and whether the symbiosis is obligatory or facultative. Tell the class about your example. For each example, fill in the table provided with the types of organism and type of symbiosis.

#1 Think back to session 2 (insert wibble wobble music here). Hummingbirds drink nectar from flowers. They carry pollen from flower to flower, resulting in pollination for the flower.

#2 Insectivorous birds travel with the elephants and eat insects which are disturbed by the passing elephants.

#3 The Egyptian plover bird and the crocodile. The bird preys on parasites that feed on crocodiles which are potentially harmful to them. The crocodile openly invites the bird to hunt on his body, even going so far as to open the jaws to allow the bird enter the mouth safely to hunt. For the bird's part, this relationship not only is a ready source of food, but a safe one considering that few predator species would dare strike at the bird at such close proximity to the crocodile.

#4 Lichens are not plants: they are a symbiotic relationship between fungi and photosynthetic algae. Most of the visible organism is fungal, but within the fungal tissues are algae. These produce nutrients which are fed into the fungal cells. The fungal cells produce chemicals which assist the algae cells to carry out some chemical processes. The fungi are unable to live alone, but lichens are able to live in very harsh environments.

#5 Rhizobia are soil bacteria that fix nitrogen (convert atmospheric nitrogen into a form that can be used by plants and animals) after becoming established inside root nodules of legumes (such as beans).

#6 Zebra travel in large herds. Insectivorous birds travel with the zebras and eat insects which are disturbed by the herd.

#7 Clown fish often form relationships with sea anemones. The territorial fish protects the anemone from anemone- eating fish, and in turn the stinging tentacles of the anemone protect the clownfish from its predators (a special mucus protects it from the stinging tentacles).

#8 Bacteria live in the digestive system (gut) of cattle and break down the cellulose so that the cattle can digest it.

#9 Honey ants eat honeydew, a by-product of digestion secreted by certain aphids. The ant usually obtains the liquid by gently stroking the aphid's abdomen with its antennae. Some species of ants collect honeydew from aphids on leaves, while others collect the aphids and carry them back to the ant colony where they ‘farm’ them.