Population genetics and speciation Flashcards
What is a population?
A group of same species living in a specific environment/area
Microevolution
The change in allelic frequencies in a population over time
Genetic variation
Phenotypic variation based on changes in genes/DNA sequences
A single globin gene underwent____and_______. Mutations resulted in __________?
Duplication and divergence
Two different functioning genes on two different chromosomes
What are fixed alleles?
When there is only one allele for a particular locus
What is the Hardy-Weinberg Equilibrium?
In a population that is not evolving, allele and genotype frequencies remain constant from one generation to another
What equation is for allelic frequencies?
1 = p + q
What equation is for genotypic frequencies?
p^2 + 2pq + q^2 = 1
What are the assumptions of Hardy-Weinberg?
- No mutations
- Random mating
- No natural selection
- Large population
- Isolated population
What is genetic drift?
Change in allelic frequencies in a small population
What is the bottleneck effect?
Catastrophic event, a large number of individuals die, the allele frequency in the new population changes drastically. Usually reduces allele variability
What is the founder effect?
When a group of individuals move to a new area and form a new population, without the original population dying
Genetic drift is significant in______?
Small populations
Genetic drift can lead to______?
A loss of genetic variation within populations
Genetic drift can cause allelic frequencies to_______?
Change at random
Genetic drift can cause harmful alleles to become______?
Fixed
Gene flow
Immigration or emigration of population
Does immigration and emigration increase or reduce genetic differences?
Reduce. Alleles are exchanged
Natural selection
If an allele is favourable, the frequency of that allele goes up in a population. If it is harmful, the frequency goes down.
The role of natural selection in the gradual adaptation of a population to its environment is an example of what kind of evolution?
Microevolution
What is the broad pattern of evolution above the species level?
Macroevolution
Why doesn’t the first species definition work?
Hybrids exist (when two species mate)
They are usually infertile and don’t survive
ex. Mules, Grolar bears, coywolf
Species definition 1: Biological species concept
A species is_____.
Formation of new species depends on_____?
A group of populations whose members can interbreed and produce fertile offspring
Reproductive isolation (no gene flow)
Species definition 2: Morphological species concept
Classification based upon______.
Physical traits like size, shape, etc.
Why doesn’t the second definition of species work?
Can lead to false clasification
Chihuahuas and Great Danes don’t look alike, but they are the same species
Species definition 3: Ecological species concept
View species in terms of______.
What type of selection can it lead to?
Its ecological niche, and how the population interacts with the non-living and living things in its environment
Ex. Oak trees. One can tolerate the dry, the other cannot
Disruptive selection
For two species to be separate, a mechanism must be in place that keeps them from breeding called?
Reproductive barriers
What are the two types of reproductive barriers?
Prezygotic barriers
Postzygotic barriers
What are the types of prezygotic barriers?
Habitat isolation: Two species in the same environment, but separate habitats so they don’t interact
Temporal isolation: Breeding at different times or seasons
Behavioural isolation: Different courtship rituals
Mechanical isolation: Physical incompatibility of reproductive parts
Gametic isolation: Molecular incompatibility of eggs and sperm
What are the types of postzygotic barriers?
Reduced hybrid viability: hybrids cannot fully develop or are unable to reproduce due to the interaction of parental genes
Reduced hybrid fertility: Healthy hybrids that cannot produce offspring
Hybrid breakdown: The first generation is viable, but the second is not
What is allopatric speciation?
When a population is divided into geographically isolated populations due to changes in geography or waterbodies
What does allopatric speciation lead to?
Founder effect
Genetic drift
Natural selection
What is sympatric speciation?
When a population is divided without geographic isolation
How does sympatric speciation arise?
Polyploidy, habitat differentiation (water temperature), sexual selection
Polyploidy
Cells that contain more than two paired chromosomes
Autoploidy
Doubling of chromosomes in the same species
Allopolyploidy
Hybridization of two different species, followed by cell division
What plant created in Manitoba was caused by allopolyploidy?
Canola
Habitat differentiation
When a subpopulation starts to use a habitat or resource not used by its parents
Can sexual selection occur both allopatrically and sympatrically? How?
Yes
Allopatric: separated populations develop new mating behaviours and if they are re-introduced, will not interbreed
Sympatric: changing mating behaviours in the same habitat will lead to restrictions in gene flow
