3.7.3- Evolution may lead to speciation Flashcards
What is evolution?
Process by which organisms become better adapted to suit their environment
What is variation?
Measure of difference between individuals (phenotype)
What is allele frequency ?
How often an allele appears in a population
What is speciation?
Formation of new species
What is the major cause of variation?
Random mutation
What are phenotypic changes caused by?
Changes in the genome
What are the sources of variation?
Random mutation
Meiosis
Phenotype changes
Random fertilisation
When is an allele most likely to be inherited ?
When it offers an organisms an advantage
What does an allele being inherited lead to?
Increase in allele frequency = natural selection
What are selection pressures ?
The changes that can cause/ force an entire population to adopt a new phenotype
What are the 3 main selection pressures?
Disease
competition
predation
What are the 3 types of selection?
Directional
Stabilising
Disruptive
What is a gene pool?
Total number of all the alleles of all the genes in all individuals within a population at a given time
What is directional selection?
Environmental selection pressures favour individuals that are different in one direction, to the mean
What is disruptive selection?
Selection pressures favour individuals with the more extreme phenotypes
What is stabilising selection?
Environmental selection pressures favour individuals that represent the mean. This will preserve the current population + extreme phenotypes are not beneficial
Define Allopatric speciation?
Species can form when they become geographically isolated, leading to different environments
Define sympatric speciation?
Does not require geographical isolation
Explain sympatric speciation?
Individuals in a species gain a characteristic (due to a mutation) that allows them to exploit a niche in the environment
The other individuals in the population, without the mutation still continue to thrive
What is artificial selection ?
Individuals are forced to breed due to humans choosing desire characteristics to be bred
Where does genetic drift occur ?
In small populations
Explain genetic drift
If an individual happens to die without reproducing then their alleles are lost from the gene pool.
Conversely, if a no. of individuals reproduce more than would be expected, then the alleles they carry would flood the gene pool
What is a genetic drift from the norm?
The result of the gains + losses of alleles can cause a change in the allele frequencies in the entire population.
