Populations and Evolution- Speciation and Genetic Drift Flashcards
What is speciation?
The development of new species from an existing species
When does speciation occur?
When populations of the same species become reproductively isolated
What causes changes in phenotype?
Changes in allele frequency
What do changes in phenotype mean?
They can no longer interbreed to produce fertile offspring
What is geographical isolation?
When a physical barrier (flood, earthquake…) divides a population of a species, causing some individuals become separated from the main population
What does geographical isolation lead to?
Allopatric speciation
What is sympatric speciation?
When a population becomes reproductively isolated without any physical separation
What will happen to populations that are geographically separated?
They will experience slightly different conditions and different selection pressures
What does populations experiencing different selection pressures mean?
Different changes in allele frequencies could occur
What do changes in allele frequencies lead to?
Differences accumulating in the gene pools of the separated populations, causing changes in phenotype frequencies
How will two populations become two separate species?
Eventually, individuals from the different populations will have changed so much that they won’t be able to breed with one another to produce fertile offspring
How may sympatric speciation occur?
By random mutations
What is seasonal reproductive isolation?
Individuals from the same population develop different flowering or mating seasons, or become sexually active at different times of the year
What is mechanical reproductive isolation?
Changes in genitalia prevent successful mating
What is behavioural reproductive isolation?
A group of individuals develop courtship rituals that aren’t attractive to the main population
