Speciation

Question 1

Species definition

Answer 1

A group of individuals who are able to mate with each other and produce viable and fertile offspring

Question 2

Viable

Answer 2

Capable of surviving

Question 3

Why can’t two different species produce fertile offspring?

Answer 3

The different species have different amounts of chromosomes each, so when they mate, their offspring inherits a diff amount from mother and diff from father - resulting in at least one chromosome without a homologous pair - not possible in meiosis

Question 4

Allopatric speciation

Answer 4

Involves the formation of new species as a result of a geographical barrier

Question 5

Geographical barrier

Answer 5

A physical factor that prevents gene flow, and so stops two populations from breeding together

Question 6

Allopatric speciation steps

Answer 6

1. A geographical barrier separates a population, preventing gene flow
2. Different selection pressures act upon each population, favouring different phenotypes and allowing for genetic differences to accumulate
3. Eventually, sufficient genetic differences accumulate so that the two populations can no longer interbreed to produce viable and fertile offspring

Question 7

Galapagos finches

Answer 7

Finches were separated by a geographical barrier - the ocean due to a cyclone, preventing gene flow between the different populations.
Each island had different selection pressures causing them to adapt to their own environment through natural selection
Eventually, sufficient differences accumulated and viable and fertile offspring could no longer be produced through interbreeding - new species of finches were formed
Despite their variation in phenotype, they were genetically closely related

Question 8

Sympatric speciation

Answer 8

Formation of a new species in populations located in the same geographical location

Question 9

Two ways sympatric speciation can arise

Answer 9

1. Different selection pressures acting on different phenotypes
2. Genetic abnormalities - polyploidy

Question 10

How does polyploidy occur?

Answer 10

Meiosis error

Question 11

Lord Howea palms

Answer 11

Two howea palms inhabited different soils, leading to speciation.
One exposed to volcanic soil (acidic), the other exposed to calciferous soil (alkaline)
The soil acted as a selecting pressure, the palms growing in the calciferous soil flowered earlier than the other one growing in volcanic soil.
This meant the alkaline and acidic plants were reproductively isolated, due to different flowering times being present preventing gene flow
Hence, after several generations and accumulation of differences, a new species was formed so they could no longer interbreed