Speciation Flashcards
What is a species?
A group of organisms that are capable of interbreeding and producing fertile offspring and which do not normally breed with other groups
What is separation in speciation?
Populations are separated by a barrier that prevents breeding
This can be geographical, reproductive or ecological
What are mutations in speciation?
Mutations occur at random
Most of the mutations affecting one population will be different from those in the other population
What are selection pressures in speciation?
Selection pressures for the two groups are different
Different characteristics will be selected for survival as some mutations may be favourable
What is natural selection in speciation?
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
What the result of speciation?
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
What are the steps of speciation?
Separation
Mutations
Selection pressures
Natural selection
Result
What are the types of speciation and their methods of isolation?
Allopatric speciation caused by:
-geographical isolation
Sympatric speciation caused by:
- behavioural isolation
- ecological isolation
What are isolating mechanisms?
Isolating mechanisms are barriers to gene flow between populations
Example of behavioural isolation
Different populations have different breeding seasons and mating calls
Example of ecological isolation
Nocturnal species
Alkalinity
What is sexual selection?
Non random increase in frequency of genetic sequences that increase reproductive success
What are hybrid zones?
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
