Genetic & Species Diversity

Variation In DNA Can Lead To Genetic Diversity

Genetic diversity exists within a species, however, DNA within a species varies very little because all members of the same species have the same genes, just different alleles. DNA of different species varies a lot because they have different genes. 

The more alleles in a poplation, the more genetically diverse it is , this can be increased by: Mutations - in DNA forming new alleles or Gene Flow - different alleles being introduced into the population when members migrate into them and reproduce.

Genetic Bottlenecks-  reduce genetic diversity, it is when there is a large reduction in a population eg a lot of them die. Only the surviors reproduce, this reduces the number of alleles in the gene pool so reduces genetic diversity.

The Founder Effect- is when just a few organisms start a new colony, so only a few contribute their alleles to the gene pool, theres also more genetic disease. Can occur as a result of migration ect.

SELECTIVE BREEDING
This is when humans select which animals/plants to reproduce to produce high yielding breeds. It reduces genetic diversity because only those which the desired charachteristic are bred so only similar organisms with similar traits and it reduces the number of alleles in the gene pool.

Selective breeding can cause problems involving ethical issues. 

• It can cause health problems, eg dairy cows have extra strain
• It reduces genetic diversity which can result in genetic disease. 

However is can be a good thing.

• It produces high yielding plants/animals.
• It can be used to produce animals/plants with increased resistance to disease so less pesticides and drugs used.
• Animals/plants can be bred to have increased tolerance to bad weather e.g drought or cold. 

SPECIES DIVERSITY- The number of species present in a community.
The higher the species diversity of plants and trees, the higher the species diversity for animals because there will be more habitats/food sources. 

Species diversity is measured using the index of diversity d= N(N-1)/En(n-1)
N= Number of ALL species n= Number of EACH species.

Deforestation (for land for farming ect) decreases species diversity. It reduces directly the number of trees species, so destroys habitats/food sources, to animals either migrate or die.  

So does agriculture (trying to maximise food produce) Woodland clearance, Hedgerow removal, Monoculture (only growing one type of plant so fewer species), Pesticides and herbicides.