Speciation

Question 0

How does one species separated by a geographical isolation become two species?

Answer 0

• due to the difference in selection pressures, different characteristics will be advantageous on each side so the allele frequencies will change in each population
• mutations will take place independently in each population, changing the allele frequency
• these changes in allele frequencies will lead to changes in phenotypic frequencies
• eventually, individuals from different populations will have changed so much that they won’t be able to breed with one another to produce fertile offspring (reproductively isolated) - become 2 new species

Question 1

What is geographical isolation?

Answer 1

• When a physical barrier divides a population of a species
• conditions on either side of the barrier will be slightly different
• because the environment is different on each side, different characteristics will become more common due to natural selection due to the fact that there are different selection pressures

Question 2

What are the different isolation mechanisms that stop a population from freely interbreeding?

Answer 2

• geographical barriers - river, mountain range
• seasonal barriers - climate change
• reproductive mechanisms - genitals may be incompatible

Question 3

What is speciation and what does it require in order to take place?

Answer 3

• it is the formation of a new species
• needs variation
• needs a selection pressure
• isolation

Question 4

What is the biological species concept?

Answer 4

A group of similar organisms that can interbreed and produce fertile offspring

Question 5

What are the problems with the biological species concept?

Answer 5

• organisms may reproduce asexually e.g. Bacteria

* may be the same species but cannot mate due to physical incapabilities e.g. Large and small dogs

Question 6

What is a monophyletic group?

Answer 6

An ancestral organism and all its descendant species

Question 7

What is the phylogenetic species concept?

Answer 7

• The smallest possible monophyletic group descended from a common ancestor with a shared trait
• it is a group of organisms that have similar morphology (shape), physiology, embryology and behaviour and occupy the same ecological niche