B2.8 Speciation

Mind Map by killthemoment, updated more than 1 year ago
Created by killthemoment over 5 years ago


GCSE Biology (B2) Mind Map on B2.8 Speciation, created by killthemoment on 08/03/2014.

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B2.8 Speciation
1 B2.8.1 Old And New Species
1.1 Changes in the environment of plants and animals may cause them to die out. The fossil record shows that new organisms arise, flourish, and after a time become extinct. The record also shows changes that lead to the formation of new species.
1.1.1 Scientists aren't certain about how life began due to lack of valid and reliable evidence. There are gaps in the fossil record as some fossils haven't yet been found, the conditions for fossilisation weren't present and early life forms were soft-bodied so they didn't form fossils. Fossils are the 'remains' of organisms from many years ago, which are found in rocks. Fossils may be formed in various ways: from the hard parts of animals that do not decay easily; from parts of organisms that have not decayed because one or more of the conditions needed for decay are absent; when parts of the organism are replaced by other materials as they decay and as preserved traces of organisms (footprints, burrows and rootlet traces). Many early forms of life were soft-bodied, which means that they have left few traces behind. What traces there were have been mainly destroyed by geological activity. We can learn from fossils how much or how little different organisms have changed as life developed on Earth. Extinction may be caused by changes to the environment over geological time, new predators, new diseases, competitors or a single catastrophic event. New species arise as a result of isolation – two populations of a species become separated, for example geographically. Due to genetic variation, each population has a wide range of alleles that control their characteristics. Natural selection occurs in each population and the organisms with desired characteristics are enabled to survive and continue to reproduce. Due to different situations, each population evolve differently and eventually the two become so distinct, they can no longer breed successfully. This is called speciation.
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