7.3 Speciation

• What is disruptive selection?

  This occurs when an abiotic factor, like temperature, takes two distinct forms. E.g. Cold in Winter and hot in Summer.
• What is a species?

  A species are organisms with similar features that can breed together to produce fertile offspring.
• What is speciation?

  Speciation is when there are major changes in the gene pool so the two species cannot interbreed and cannot produce fertile offspring.
• What is allopatric speciation?

  This is when a new species forms from different populations in a different area - They're been physically isolated.
• What is sympathetic speciation?

  This is when a new species form which are reproductively isolated from the same population.
• Describe allopatric speciation. [6]

  There are different populations and thus different gene pools become geographically isolated in different areas, a random allele mutation occurs which increases the allele variation. As the two populations evolve under different selection pressures, different advantageous alleles (after a mutation) are passed on to the next generations *name the phenotype*, these organisms will survive and reproduce. The frequency of favourable alleles changes, leading to a separation of gene pools (a new species), this new species cannot breed to produce fertile offspring.
• Describe sympatric speciation. [6]

  These are individuals of the same population and therefore the same gene pool, within this population a random allele mutation occurs which results in reproductive isolation. Different alleles are selected and passed to the next generation, leading to a separation in gene pools which cannot interbreed to produce fertile offspring.
• What is the difference between allopatric speciation and sympatric speciation?

  In allopatric speciation the two populations evolve under different abiotic and biotic conditions, meaning that they have different selection pressures.
• Genetic drifts in small populations.

  In a small population there are only a small number of alleles which leads to less genetic diversity. There is not an equal chance of each allele being passed on and so frequencies can change quickly, causing a genetic drift. Any allele that is advantageous will quickly increase in frequency and this increases the rate of speciation in small populations.