Speciation Flashcards
What is speciation ?
the formation of new species from pre-existing species over time (as a result of changes to gene pools from generation to generation)
What is Allopatric speciation ?
New species form from different populations in different areas.
What causes Allopatric speciation ?
Geographical isolation
What is geographical isolation ?
occurs when populations of species become separated from each other by geographical barrier.
creates two populations of the same species who are reproductively separated from eachother.
What are the key points on Allopatric speciation ?
Geographical isolation separates two populations; there is no interbreeding/ gene pools are separate due to physical barrier
Mutation occurs and gives variation within the population
different environmental conditions influence the selection pressures on the alleles.
Different selection pressures operate and different alleles are selected for and passed on.
Beneficial allele selected for causing the allele frequency to change.
leads to reproductive separation.
new species formed.
Eventually the different species cannot interbreed to produce fertile offspring.
What is sympatric variation ?
is the formation of a new species due to reproductive isolation in a population (living in the same area) without geographical isolation
What are the key points on sympatric speciation ?
no geographical isolation occurs.
mutation occurs, this leads to reproductive separation and there is no gene flow.
No interbreeding: may be reproductively isolated
the same environmental conditions exist however there will be different selection pressures operating and different alleles are selected for and passed on.
beneficial allele will be selected for causing the allele frequency to change.
population already reproductively isolated.
new species formed
eventually different species cannot interbreed to produce fertile offspring.
What does genetic drift cause ?
changes to allele frequencies in small populations
Describe genetic drift
the small population with low genetic diversity will breed together and the genetic diversity is restricted.
This leads to a high frequency of a few alleles
if an individual happens to die without reproducing, the alleles they carried are lost.
similarly, if a small group of the population reproduce more than would be expected, then the alleles they carry will flood the gene pool.
The result is that the gains or losses of these individuals cause a substantial change in the allele frequency of the entire population- genetic drift from the norm.
What are the two ways genetic diversity in a population can be reduced ?
Genetic Bottleneck
The founder effect
What is the founder effect ?
small group of individuals from a large parent population start a new population.
As the new population is made up of only a few individuals from the original population only some of the total alleles from the parent population will be present.
Results in a loss of alleles from gene pool.
What is the genetic bottleneck effect ?
environmental factor- such as natural disaster.
results in a lots of individuals being lost from a population.
reduces the number of individuals in a population
only surviving individuals can reproduce.
genetic diversity reduced as alleles have been lost from the gene pool.
Surviving individuals end up breeding and reproducing with close relatives.
