Allopatric speciation

Question 1

How does allopatric speciation occur?

Answer 1

• more common form of speciation
• happens whne some mebers of a population are separated from the rest of the group by a physical barrier
  
  • geographically isolated
• *

Question 2

What is allopatric speciation?

Answer 2

• environments will be different so the selection pressures will be different
  
  • resulting in different physical adaptations
    
    • often lead to the founder effect leading to genetic drift
    • enhancing the differences between the populations

Question 3

What is an example of allopatric speciation?

Answer 3

• finches inhabiting the Galapagos ISland
  
  • once together in mainland
  • stranded on different island
  • separated by the sea
  • new colonies formed
• evolved and adapted to the different environments, particularly food sources
• example of adaptive radiations
  
  • where rapid organism diversification takes place
• evolved unique beaks
  
  • adapted to type of food available
  • e.g. large blunt beaks to crack nuts, long thin beaks to get nectar from flowers

Question 4

When does sympatric speciation occur?

Answer 4

• sympartic occurs within population that share the same habitat

Question 5

Where is sympartic speciation occur?

Answer 5

• less frequently than allopatric speciation
• more common in plants than animals

Question 6

How does sympartic speciation occur?

Answer 6

• when two different species interbreed and form fertile offspring
• the hydbrid formed, which is a new species, will have a different number of chromosomes to either parent and may no longer be able to interbreed with memeber of either parent population
• this stops gene flow and reproductively isolates the hybrid organisms

Question 7

How are blind mole rats an example of sympartic speciation?

Answer 7

• different types of soils support a different range of plants
• blind mole rats found in both types of soil are sometimes separated by a few metres of loose soil
• mole rates will only interbreed with mole rats living on the same type of soil
• lack of gene flow is causes genetic difference
• these could accumulate to the point where the mole rats are no longer able to breed

Question 8

What are reproductive barriers?

Answer 8

• barriers to successful interbreeding can form within populations before or after fertilisation has occured
• prezygotic reproductive barriers prevent fertilisation and the formation of a zygo
• postzygotic reproductive barries, often as a reuslt of hybridisation, reduce the viability or reproductive potential of offspring