Natural Selection & Biodiversity

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  • Created on: 18-03-13 21:19
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NATURAL SELECTION
Useful adaptations become more common in populations of species because of evolution by natural selection:
1. Individuals within a population show variation in their phenotypes.
2. Predation, disease and competition create a struggle for survival.
3. Individuals with better adaptations are more likely to survive, reproduce and pass on their advantageous adaptations to their offspring.
4. Over time, the number of individuals with the advantageous adaptations increases.
BIODIVERSITY
A measure of the variety of living organisms in a habitat and their genetic differences.
ENDEMISM
When a species is unique to a single place e.g. the giant tortoise is endemic to the Galapagos Islands. Conservation is really important for endemic
species because they're particularly vulnerable to extinction and if their habitat is threatened they can't usually migrate and their numbers will decline.
Measuring Biodiversity
SPECIES RICHNESS:
Counting the number of species present in a particular habitat. HOWEVER, it takes no account of the population size of each species.
SPECIES EVENESS:
Counting the number of each species population. This takes into account the number and abundance of each species
It would be too time consuming to count every individual organism so a sample is used; it needs to be random to avoid bias

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Sampling Methods:
Quadrats: counting individuals and calculating a percentage cover.
Mark-Release-Recapture: Use proportion of marked in recapture to estimate whole population.
You can measure diversity within a species by looking at genetic diversity; the variety of alleles in the gene pool of a species. This can be
done by:
DNA sequencing to determine the bases in a segment of DNA, and thus to determine which alleles are present.
Cutting the DNA into fragments and then separating them by using electrophoresis.…read more

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