Speciation

Question 1

What is a species?

Answer 1

A group of organisms that are capable of interbreeding and producing fertile offspring and which do not normally breed with other groups

Question 2

What is separation in speciation?

Answer 2

Populations are separated by a barrier that prevents breeding

This can be geographical, reproductive or ecological

Question 3

What are mutations in speciation?

Answer 3

Mutations occur at random

Most of the mutations affecting one population will be different from those in the other population

Question 4

What are selection pressures in speciation?

Answer 4

Selection pressures for the two groups are different

Different characteristics will be selected for survival as some mutations may be favourable

Question 5

What is natural selection in speciation?

Answer 5

Over a very long period of time natural selection causes the two groups to become genetically distinct

This is a non random increase in the frequency of genetic sequences that increase survival

Question 6

What the result of speciation?

Answer 6

The isolated population becomes so different from the original population that successful interbreeding can no longer take place

If the barrier is removed the two groups can no longer interbreed to produce fertile offspring

A new species has been formed

Question 7

What are the steps of speciation?

Answer 7

Separation

Mutations

Selection pressures

Natural selection

Result

Question 8

What are the types of speciation and their methods of isolation?

Answer 8

Allopatric speciation caused by:
-geographical isolation

Sympatric speciation caused by:

• behavioural isolation
• ecological isolation

Question 9

What are isolating mechanisms?

Answer 9

Isolating mechanisms are barriers to gene flow between populations

Question 10

Example of behavioural isolation

Answer 10

Different populations have different breeding seasons and mating calls

Question 11

Example of ecological isolation

Answer 11

Nocturnal species

Alkalinity

Question 12

What is sexual selection?

Answer 12

Non random increase in frequency of genetic sequences that increase reproductive success

Question 13

What are hybrid zones?

Answer 13

A region may be occupied by several populations of an organism which vary in their ability to interbreed

This forms hybrid zones

A population can interbreed with its immediate neighbour to form fertile hybrids

Genes can flow between populations