Module 1 Flashcards
What is evolution?
Descent with inherited modification
Gain and loss of traits
What is small scale evolution?
Changes in allele frequencies in a population
What is large scale evolution?
The descent of different species from a common ancestor
How do we know evolution occurs?
Fossil evidence
Homologous structures (& vestigial structure- pelvic bone in whales)
Observing evolution
What are the four mechanisms of evolution?
Mutation
Genetic drift
Migration
Natural selection
What is mutation?
RANDOM changes in DNA sequences
Can be good, bad, or neutral
Is mutation heritable?
Depends, if the mutation occurs in a reproductive cell it can be passed on to offspring
What causes mutation?
Mutation occurs at a predictable rate, the body has mechanisms to correct this, some factors increase the risk that mutations will slip past the body’s corrective mechanisms (UV light, nicotine, alcohol, etc.)
Why is mutation important for natural selection?
All variation- the raw material for natural selection- must initially come from mutation
What is genetic drift?
Random change in allele frequencies in a population
How does genetic drift occur?
Founder effect & bottleneck effect
Genetic drift does not provide advantage or disadvantage for reproductive success
What is fixation?
A consequence of genetic drift when an allele frequency reaches 100%
Reduces variation in a population
What is the founder effect?
When a subgroup splits off from a main population and set the alleles of the new population
What is the bottleneck effect?
A population size is reduced (natural disaster) and variation is reduced
What is migration?
Gene flow into or out of a population changing the allele frequencies in both original and recipient populations
What conditions allow natural selection to occur?
Variation for a trait
Heritability
Differential reproductive success
What is differential reproductive success?
When some individuals have genetic traits that make them more likely to pass on these traits to future generations
What is fitness?
Reproductive success measured relative to other individuals in a population
Variation causes some individuals to have better fitness than others
How does the environment impact fitness?
Different environments have different selective pressures
What is adaptation?
When a trait becomes common/fixed in a population because it has a fitness advantage
The only evolutionary mechanism that can result in adaptation is natural selection
What is speciation?
A gradual change over time that results in populations that can no longer interbreed with one another
What is the biological species concept?
Species are a group of organisms that can potentially interbreed and produce viable offspring
What keeps biological species separate?
Reproductive barriers (prezygotic and postzygotic)
What are prezygotic barriers?
Individuals are physically unable to mate
If individuals can mate, the male sperm cell is unable to fertilize the female egg cell
CANNOT FORM A ZYGOTE
