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The body has many ways in which it deals with 'foreign invaders', like a rhinovirus (the virus responsible for the common cold). Once an infective micro-organism enters the body, lots of different cell t...

gas exchange occurs in the alveolus of the lungs. Alveoli provide a good surface for gas exchange to take place.They provide a large surface area to volume ratio which increases the amount of gas that can...

Eutrophication is the process whereby excess fertiliser is added to fields by farmers. This fertiliser contaisn nitrates which are very sioluble and so easily runs off into rivers and lakes. Plants use ni...

Primary succession begins with newly formed land such as bare rock of volcanic island.  Pioneer species such as lichens and mosses colonise the rock. When these pioneer species die organic matter builds u...

Osmosis is the free movement of water molecules across a partially permament member from high water potential to low water potential, down the water potential gradient, without the input of energy.