Variation and evolution

YELLOW-thing/examples that could come up in exam. GREEN PINK

In this topic we will go through a species need variation to survive.Some caharcteristics are monogenic (discontinuous) and not inflenced by the environment. Whilst others are polygentic (continuous) ,varing from a range of values , but only one vaule will be expressed depending on the environment organism is.

Variation

Organisms can differ in their phenotype due to 3 reasons:

• Different genotype
• Different environments
• Same genotype ,different epigenetic modifications

Variation is reffered to as the difference in the phenotypes within a species.

If genetic variation is down to different nucleotide bases or different epigenetics modifications(in some cases) ,the variation is heritable.

In asexual reproduction heritable variation increases by:

• Mutation

In sexual reproduction heritable variation increases by:

• Independant assortment
• Fusion of two different parent gametes/genotypes during fertilisation 
• Random distubution: of chromosome in meisos 1,Of chromotids in meiosis 2
• Crossing over -during prophase1

New combinations of alleles occur in each generation due to these processes.Mutations (which are rare by definition) give rise to long lasting variation of the novel kind.

Non heritable variation is variation that is due…