more on biodiversity

induviduals within a species differ from one and other - they show variation.

all organisms apart from cloned organisms and twins have a set of unique alleles - this is known as genetic diversity.

the greater the number of genotypes the more genetically diverse the population.

genetic dversity allows the population to adapt to new conditions so is very important.

meiosis results in genetic variation through independant assortment and crossing over.

random mutations also generate genetic variation by changing the DNA sequence in the cells of an organism,creating new alleles. genetic diversity is increased with the addition of these new alleles to the gene pool.

most mutations have no affect of the phenotype of an organism, some have harmful affects and some have beneficial affects.

the simplest way to measure biodiveristy is to count the number of species present in a habitat. this is called species richness.

for example a wood in england may have 25 butterfly species, but a south american rainforest may have 100 butterfly species. so we say that the S.american rainforest has more biodiveristy than the wood.

species richness can be useful, however it takes no count of the population size for each species.

a community in which most of the species have similar abundances is said to have high eveness

A highly diverse community would have high species richness and high species eveness.

A very common species within a habitat is sometimes said to be the dominant organism.

the worlds biodiveristy is not distibuted evenly across the planet.

for example the biodiveristy hotspot containing the largest proportion of the planets plant species is the mediterranean basin.

the term 'biodiveristy hotspot' described an area with a particularly high biodiversity.

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genetic diversity can be measured directly or indirectly.

the direct method is by DNA sequencing to determine the bases ina segment of DNA, and thus determining which alleles are present.

alternatively the DNA can be cut into fragments and then separated using electrophoresis - different alleles can be identified because they produce fragments of different lengths.