3.6 Evolution of species
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What is the definition of mutation?
A mutation is a random change in the structure of genetic material
How can mutations be increased?
Can be increased by mutagenic agents such as : Radiation e.g x-rays, uv light Chemicals e.g nicotine, colchicine
Name the 3 results of mutation
Harmful - genes that will decrease population Beneficial - genes that may improve population Neutral - no advantage or disadvantage
Describe variation
Makes it possible for a population to evolve over time in response to changing environmental conditions
Describe natural selection/ survival of the fittest
The best adapted organisms within a population, with characteristics best suited to the environment survive, reproduce and pass on genes to offspring.
What is speciatiation ?
The formation of new species after part of the population becomes isolated by an isolation barrier
What are the 3 types of isolation barrier?
Geographical - rivers and mountains Ecological - different habitats, soil pH Behavioural - differences in courtship behaviour, physical differences.
Speciation summary
I Must Not Smoke I solation barrier M utations N atural selection S peciation
Stage 1 of speciation
a large inter-breeding population with a common gene pod
Stage 2 of speciation
An isolation barrier appears preventing the flow of genes
Stage 3 of speciation
Different mutations appear in each subpopulation
stage 4 of speciation
Different selective pressures favour some mutations which become more common in the sub population
Stage 5 of speciation
Over many generations barrier is removed, left with two different species who can no longer inter-breed