isolation and speciation

Question 1

what is a species

Answer 1

-organism with potential to interbreed to produce viable, fertile offspring
-a group of organisms with similar morphology (body form), function, biochemistry, behaviour and genetic make up

Question 2

what is gene flow

Answer 2

in a species genes are mixed in new combinations with every generation, new mutations are shared throughout the species in a gene pool

there is no gene flow between different species, they are different gene pools

Question 3

what is speciation and what does it involve

Answer 3

-process by which new species are formed
-involves isolation (geographical and reproductive)

Question 4

explain allopatric/ geographical speciation

Answer 4

• result of geographical isolation and natural selection
  -when a physical barrier divides a population e.g mountain ranges, flood separating two areas, volcanic eruption, earthquakes, large lakes

-conditions either side of barrier will be slightly different = different selection pressures
-natural selection occurs, better adapted organisms survive, reproduce and pass on beneficial alleles = alleles in the 2 areas will be different and therefore the allele frequencies will change

-eventually individuals in the 2 populations will have changed so much that they can no longer interbreed to produce fertile offspring = 2 different species

Question 5

explain sympatric speciation

Answer 5

-species not geographically isolated, results from reproductive isolation
- Random mutations could occur = change alleles and phenotypes = can cause reproductive isolation = members with the mutation may not be able to successfully interbreed with the rest of the population

Question 6

explain the different examples of mutations that cause reproductive isolation

Answer 6

Biological causes:
-mechanical isolation:
random mutations may lead to changes in the structure of the flowers or in animals the genitalia may be altered making them incompatible

-gamete incompatibility:
random mutation may lead to a change in chromosome number preventing fusion of gametes

-hybrid inviability/ infertility
zygotes being less viable or hybrid offspring produced may be infertile

Behavioural causes:
-Temporal isolation:
two species mate at different times of the day/year, mutations may lead to changes in activity

-Behavioural isolation:
different courtship behavious or mate prferences