Unit 7 Flashcards
What happened to the finches that colonized the Galápagos Islands
They diversified and gave rise to new species
Natural selection acts on
Traits that lead to survival and reproduction
Organisms don’t evolve,…
Populations do!!
Other term for evolution
Descent with modification
What is natural selection
A process in which individuals that have certain traits tend to SURVIVE AND REPRODUCE at higher rates than other individuals because of those traits
Natural selection also acts on
Phenotypic variations in populations
“Fitness” is measured by
Reproductive success
What are adaptations
Inherited characteristics of organisms that enhance their survival and reproduction
2 observations that natural selection is based on
1 traits are heritable
2 more offspring are produced than can survive
What does more offspring being produced than can survive mean?
There’s competition for limited resources which results in differential survival
Favorable traits
Accumulate in the population
What’s artificial selection
The selective breeding of domesticated plants and animals to encourage the occurrence of desired traits
What’s a population
A group of individuals of the same species that live in the same area and interbreed to produce FERTILE offspring
What’s the gene pool
A populations genetic makeup, consists of every type of allele
Explain fixed alleles
If there is only one allele present for a particular locus in the population it is fixed; many fixed alleles = less genetic diversity
Micro evolution
Small scale genetic changes in a population
Evolution is driven by random occurrences like…
Mutations, Genetic Drift, Migration/Gene Flow, Natural Selection
Mutations are
Changes in your nucleotide sequences that deviate from what is “normal”
Mutations can result in
Genetic variation, they can form new alleles
Mutation rates
Tend to be slow in plants and animals and high in prokaryotes due to fast generation time
Most mutations are
Neutral or harmful
What’s genetic drift
Chance events that cause a change in allele frequency from one generation to the next; most significant in small populations
Why can genetic drift be bad?
It can lead to a loss of genetic variation and cause harmful alleles to become fixed
Types of genetic drift
Bottleneck effect, founder effect
Bottleneck effect is
When a large population is drastically reduced by a NON-SELECTIVE DISASTER (natural disasters, hunting); some alleles may become overrepresented, underrepresented or absent; if one allele survives over another it’s considered fixed
What’s founder effect
When a few individuals become isolated from a large population and establish a new small population with a gene pool that differs from large population (lose genetic diversity)
What’s gene flow
The transfer of alleles into or out of a population, alleles can be transferred between populations
Ex: pollen being blown to a new location
Directional selection
Selection towards one extreme phenotype
Stabilizing selection
Selection towards the mean and against the extreme phenotypes
Disruptive selection
Selection against the mean; both phenotypic extremes have the highest relative fitness
Sexual selection
Explain why many species have unique/showy features; males have useless, potentially harmful structures that show they are good mates because they were able to survive at a disadvantage
Hardy Weinberg Equilibrium is only good for populations that are
Not evolving!!!!
What’s the purpose of Hardy Weinberg Equilibrium
Results can be compared with real data, if it is the same there is no evolving, if it is different there MAY BE evolving
Conditions for Hardy Weinberg Equilibrium
1 no mutations
2 random mating
3 no natural selection
4 large population size
5 no gene flow
What happens if a Hardy Weinberg equilibrium condition isn’t met?
Microevolution occurs
Why is genetic variation good
The more genetic diversity, the better the population can respond to changes in the environment
What happens to species with low genetic diversity
They are at risk of extinction
