Evolution Flashcards
Darwin’s 4 points of natural selection
- There is variation among individuals of populations
- Some of that variation is inherited
- Populations tend to produce more offspring than the environment can support
- Those individuals whose traits best adapt them to the environment will survive better and leave more offspring
Evidence for evolution (4)
- The fossil record- changing life forms deposited in rock
- Biogeography- animals in some locations are more alike
- Comparative anatomy- convergent evolution
- Molecular biology- similar DNA/RNA sequences
Proximate explanation
Answers the question what or how, can be used to explain how the body works.
Ultimate explanation
Answers the question why. Why do we get sick?
How is fitness measured?
By reproductive success. For something to be impacted by evolution it must impact survival related to evolutionary success.
P
Frequency of the dominant allele in the population
q
Frequency of the recessive allele in the population
p^2
Percentage of homozygous dominant individuals
q^2
Percentage of homozygous recessive individuals
2pq
Percentage of heterozygous individuals.
Gene
Location on your DNA that codes for a protein.
Allele
Version of a gene.
Dominant allele
Will be expressed over a recessive allele. A recessive allele will only be expressed if homozygous.
Evolution
- Descent with modification
- Individuals do not evolve, populations do
- Occurs as the number of certain alleles increases or decreases over time.
Gene pools
- Populations make up gene pools
2. All the alleles found in a population
Allele frequency
- Proportion of an allele in a population
- Evolution involves the change of allele frequencies
- The sum of the frequencies must always equal 1.
Hardy Weinburg Principle
- Developed to help explain why dominant genes can be rarely expressed
- Both allele and genotype frequencies will remain unchanged unless outside forces change those frequencies
- Without any interference genotypes will not change
Restrictions to the Hardy Weinburg Principle
- Mating must be completely random
- There can be no mutation
- No immigration
- Population must be infinitely large
- No selection can act on the population
- Alleles must segregate according to Mendel’s first ;aw
Sources of genetic variation
- Genetic recombination
- Independent assortment
- Mutation- the only source of new genetic variation
Stabilizing Selection
- Extremes have the lowest fitness
2. Most genotypes fall in the middle, like a bell curve
Directional selection
- Removes one end of the phenotypic range
2. Only peacocks with colorful tails will mate successfully
Disruptive selection
Selection against the intermediate types, and selection for the extremes.