Selection And Speciation Flashcards
Describe natural selection
- Variation due to mutation resulting to formation of new alleles.
- Differential selection pressures such as abiotic and biotic factors
- Differential reproductive success as those who are better adapted to the environment are more likely to survive and reproduce
- These organisms are more likely to pass on their alleles
- Those who are less likely to survive are less likely to pass on the all
- Increase in allelic frequency overtime
Other type of selection?
- Stabilising = favours average
- Directional = favours one extreme
- Disruptive = favour both extremes
Describe disruptive selection?
- Selection against the average.
- Both extreme phenotypes have increased reproductive success as improved survival and ability to reproduce and find a mate
- Alleles For both passed onto future generations in greater numbers
- Overtime the frequency of both extreme allows coding for extreme phenotype increases
- Allele frequency coding for mean phenotype decreases
Name three sources of genetic variation
- Mutation= change in DNA nucleotide base sequence forming new alleles
- Meiosis= Crossing over an independent segregation in first meiosis division
- Random fertilisation of gametes during asexual reproduction
Mutation definition
Changes to the DNA nucleotide base sequence forming new alleles
Define allopatric speciation
Formation of new species from different populations in different areas
Define Sympatric speciation
Formation of new species from reproductive isolation in a population living in the same area
Describes Sympatric speciation
1.organisms within the same population in the same area but gene pools are separate. Not geographically isolated but a reproductively isolated
2. by named isolating mechanism
3. This phenotype only made to this phenotype and this phenotype only mates with this phenotype
4. Mutation causes variation forming different alleles
5. Different ales pass on to each reproductively isolated group
6. This changes allelic frequency
7. This is disruptive selection
8. Eventually become different species that cannot interbreed to produce fertile offspring
Describe allopatric speciation
- Organisms in different population so gene pools are separate.. geographically isolated leads to reproductive isolation
- This is all Patrick spec
- Mutation causes variation forming different alleles in different populations
- Different selection pressures due to abiotic abiotic factors
- Selection for different advantage all that increases survival so all is passed onto next generation
- When adapted organisms within the population breed and reproduce
- Changes in all frequency
I8. Eventually become different species that cannot interpret to produce fertile Springs
What is temporal isolating mechanism?
Different breeding Season or feeding times
What is ecological or behavioural isolating mechanism?
Different courtship behaviours, niche habitats feeding areas
What is mechanical isolating mechanism?
Mismatch of reproductive parts
What is hybrid infertility isolating mechanism?
Hybrid has a odd number of chromosomes so bivalence and no separation of homologous chromosomes as no meiosis
What is gamete compatibility isolating mechanism?
Sperm killed in female reproductive tracts and can’t fuse with egg
