Examples Flashcards
An example of a phenotype
How tall a giraffe is
How fast a plant grows
If a rat is agresiva or take
Where does genetic variation come from
Mutations and recombination (meiosis)
Where does phenotype come from?
Genotypes variation and environmental variation
Frequencies
All frequencies have to add up to 1
There is a new mutation what will happen next?
It depends:
• If the new variation increases or decreases : natural selection
• If the population is big or small : genetic drift
• if the individuals in the population are mating randomly or not : non random mating
Once there is variation in a population, what can change how common it is?
Hint: natural forces
- natural and sexual selection
- genetic drift
- gene flow
- non random mating (inbreeding)
If a genetic variant decreases fitness, we expect this variant to?
Become less common through time
If a genetic variant increases variant, we expect this variant to ?
Become more common through time
3 conditions of natural selection:
- variation in population
- variation leads to higher fitness
- variation is heritable
Sexual selection
Some individuals have more access to mates than others. This leads to higher fitness
Important hint of genetic drift
Occurs when populations are small
Explanation of genetic drift
Because the population is small some variants (by chance) don’t get passed from one generation to the next. It becomes less variable as one allele becomes more common
Genetic drift is random
What allele becomes most common is random
If two populations are evolving due to genetic drift, they will become less similar
What are chance events?
Anything that reduces the size of a population:
• bottleneck
• founder effect
• geographic barriers
Example of bottleneck
A natural disaster
Human hunting
An example of founder effect
A few individuals from a population colonize a new island and start life there
A few individuals from a population colonize a new part of the world
An example of geographic barriers
The highways that split up all the populations of animals into smaller populations
Gene flow populations
Each population becomes more variable
The two populations exchange Individuals become more similar
Example of gene flow
Florida panther was experiencing genetic drift so humans brought Texas panthers to mate with them. It increased the variation in the Florida cats
Explantation of non random mating
Inbreeding is an extreme example
It tends to decrease variation with in a population
Examples of non random mating
Royal families liked to inbreed to keep the wealth in the family
There are lizards that reproduce with themselves. The species only consists of females
What are the main two ways to determine if a gene or trait is evolving ?
Visually see if the frequency of the allele/ phenotype is changing through time, of it is, its evolving
Use the hardy Weinberg equilibrium
The hardy Weinberg only applies when
The population is NOT evolving
How to use the hardy Weinberg equilibrium
- Get the data on REAL genotypic frequency
- Calculate allele frequency
- Use the equation to calculate expected genotypic frequencies
- Compare real to expected data
- If they are similar, it’s not evolving
If it’s different, it’s evolving
