Chapter 8 - Evolution Flashcards
On which level does evolution operate?
On populations, NOT on individuals
What is evolution?
When the allele frequency in a population change
What are the 4 main points or Darwin’s theory of evolution?
- Organisms change over time
- Some organisms have gone extinct
- The Earth is 6000+ yrs old
- The geology of Earth is not constant, but always changing
What are the 4 mechanisms that can give rise to evolution?
1-Mutation
2-Genetic drift
3-Migration
4-Natural Selection
What are 2 ways to alter a population?
Breeding (selective or not)
Immigration (adding/removing individuals)
What is a mutation?
A direct change in the DNA sequence of an individual - it is the ultimate source of genetic variation
- We can’t predict which individuals will have mutations
- We cant predict what are going to be the consequences of the mutations
What is genetic drift?
A random change in allele frequencies in the population over time (neither allele have better success than the other)
What is fixation?
When an allele’s frequency becomes 100% in a population
Name and explain 2 ways that genetic drift can occur
1- Founder effect: A small number of individuals may leave a population and become the founding members of a new, isolated population, and bring with them their specific genetic variation (not the same as the original pop variation)
2. Bottleneck effect: catastrophy (famine, disease, environmental change) causes the death of a large number of individuals, and the new population has different alleles than the original population
What is migration?
Gene flow in or out of a population may change allele frequencies
What are the 3 factors required for natural selection to happen?
- There must be variation for the trait within a population
- That variation must be inheritable (inheritance/heritability)
- *Individuals with 1 version of the trait must produce more offspring than those with a different version of the trait (differential reproductive success)
What are the 2 formulas of the Hardy-Weinberg Law?
p = dominant allele A q = recessive allele a p+q=1 (pp) = homozygous dominants (AA) (qq) = homozygous recessives (aa) 2pq = heterozygotes (Aa)
What are the conditions required for the Hardy-Weinberg equilibrium (when allele frequency proportions stay the same)?
- No natural selection
- No mutations
- No migration
- No genetic drift
- Random mating
What is fitness?
A measure of the relative amount of reproduction of an individual with a particular phenotype, compared with the reproductive output of individuals of the same species with alternative phenotypes
What are the 3 important elements of fitness?
- An individual’s fitness is measured relative to other genotypes or phenotypes in the pop.
- Fitness depends on the specific environment in which the organism lives
- Fitness depends on a organism’s reproductive success compared to other members of the population
What is adaptation?
The process by which organisms become better matched to their environment and the specific features that make an organism more fit (environment has to be considered when considering fitness)
What is artificial selection?
A case of natural selection where humans decide which traits are successful rather than nature
What is trait categorization?
traits can be specific (yellow or white) or continuous (height)
What is directional selection?
selecting a trait in one specific direction (ex: poultry with increasing breast size)
What is stabilizing selection?
individuals with intermediate phenotypes are the most fit
What is disruptive selection?
Individuals with extreme phenotypes experience the most fitness, and those with intermeditate phenotypes have the lowest
What are the 4 ways in which natural selection can change the traits in a population?
1- trait categorization
2- Directional selection
3- Stabilizing selection
4- Disruptive selection
What are the 5 primary lines of evidence for evolution?
1- Fossil record (using radiometric dating)
2- Geographic patterns of species distribution reflect specie’s evolutionnary history (biogeography)
3- Comparative anatomy reveal common evolutionnary origins
4- Molecular biology reveals that common genetic sequences link all life forms
5-Laboratory and field experiments enable us to watch evolution in progress
What is convergent evolution?
different types of organisms evolve to have similar traits because their environment is very similar (even though they are geographically separated)
