Alison Cox 13AX
Succession
Succession is where a pioneer species colonise an area, and gradually bring about changes so that other more complex species may also colonise the area, replacing the pioneers. The presence of the pioneer species signifies primary succession, which is basically the colonisation of bare rock. The abiotic conditions are extreme, with a very harsh climate which can only be survived by the pioneer species.
An example of a pioneer species is lichen, which are found in the splash zone of a shore. The abiotic conditions of the splash zone are extremely harsh, with fluctuating temperature and prolonged exposure to sunlight causing desiccation. Lichen is well adapted to survive these conditions, as it’s actually two organisms forming a mutualistic symbiotic relationship. Fungus and algae live together, which is beneficial to both organisms. The algae photosynthesises, which provides carbohydrates for itself and the fungus. The fungus has hyphae, which provides anchorage for the lichen as it can get into tiny cracks in the rock. It also takes in water through osmosis, and even minerals. The hyphae even protect the lichen from desiccation, as it forms a mat which protects the lichen. Physical and chemical weathering allow colonisation to begin. For example, when freeze/thaw causes cracks to appear in the rocks, they provide ideal sheltered areas for colonisation. Also, as rainwater is slightly acidic, wears down the rocks, also causing suitable conditions.
