TOPIC 7B Flashcards
What is the allele frequency?
How often an allele occurs in a population.
Its usually given as a percentage of the total population or a number
What are the 6 conditions for whether the hardy-weinberg prediction is true?
- Large or infinite population
- No immigration
- No emigration
- No mutations
- No natural selection
- Random mating
Give the 2 hardy-weinberg equations.
p + q = 1
p^2 + 2pq + q^2 = 1
(see page 164 in the revision guide)
Answer the 2 examples in page 165 in the revision guide.
Correct?
What can variations be caused by?
- mutation
- crossing over, independent segregation
- random fertilisation
- differences in the environment
(see page 166 in the revision guide)
Describe how natural selection works.
detailed description
(see page 166 in the revision guide)
Describe stabilising selection.
(see page 166 in the revision guide)
Describe directional selection.
(see page 167 in the revision guide)
Describe disruptive selection.
(see page 167 in the revision guide)
What is speciation?
Speciation is the development of a new species from an existing species.
Speciation occurs when populations of the same species become reproductively isolated - changes In the frequency cause changes in phenotype, which means they can no longer interbreed to produce fertile offspring.
What is geographical isolation?
This can happen when a physical barrier, e.g. a flood or an earthquake, divides a population of a species, causing some individuals to become operated from the main population.
This leads to allopatric speciation.
Describe allopatric speciation.
(see page 168 in the revision guide)
Describe sympatric speciation.
(see page 168 in the revision guide)
What three main factors can cause reproductive isolation?
- Seasonal
- Mechanical
- Behavioural
(see page 169 in the revision guide)
What is genetic drift?
Speciation due to chance.
see page 169 in the revision guide
