Lecture Notes- Darwin and other big ideas Flashcards
What is evolution?
change in genetic composition of populations over time
Change in genetic composition of populations over time
Evolution
Evolutionary change is observed in (blank)
Lab experiments, natural populations, and fossil record
Genetic changes drive (blank)
origin and extinction of species and the diversification of life
What is evolutionary theory?
Understanding of the mechanisms of evolutionary change
Ways to apply evolutionary theory:
- understanding and treating diseases
- understanding the diversification of life and how species interact
- developing better agricultural crops and industrial processes
- predictions about bio world
What supports the factual basis of evolution?
a vast array of geological, morphological, and molecular data
What was Charles Darwin on for 5 years?
HMS Beagle
study of organisms in environment
natural history
Darwin’s Galapagos islands observations
species were similar to, but not the same as, species on the mainland of South America and that species varied island to island
After observing the Galapagos islands, what were Darwins initial thoughts?
species reached islands form mainland but underwent different changes on different islands
3 tenants of Darwin’s evolutionary theory:
- species change over time
- Divergent species share a common ancestor, and species have diverged gradually over time (descent with modification)
- mechanism produces change is natural selection
Natural selection
the differential survival and reproduction of individuals based on variation in their traits
What did Darwin publish? When?
“Origin of Species”- 1859
Origin of Species
-provided EXHAUSTIVE evidence from many fields supporting both the premise of evolution itself and the role of natural selection as a mechanism of evolution
Genetic variation contributes to (blank)
phenotypic variation
In order for a population to evolve, members must possess (blank)
heritable genetic variation
different forms of genes
alleles
alleles exist at
locus
sum of all copies of all alleles at all loci in a population
gene pool
How do scientists date ancient events?
geological time scale
Mechanisms of evolution
- mutation
- gene flow
- genetic drift
- nonrandom mating
mutation adds (blank) to the gene pool
new alleles
gene pool
all genes in population that make up genotype
proportion of an allele in the gene pool
allele frequency
proportion of each geneotype in the population
genotype frequency
calculation of allele and genotype frequencies is used to measure
evolutionary change
purposeful selection of specific phenotypes by humans
artificial selection
example of artificial selection
wild mustard plant
Darwin observed what in domesticated plants and animals, specifically what animal?
artificial selection-pigeon
artificial selection reveals (blank)
genetic variation
natural selection is also known as
survival of the fittest
trait that increases the chance that a given individual will survive and reproduce, increasing the frequency of the trait in the next generation
adaptation
aquisition of trait that allows for better survival and reproduction in environment
adaptation
natural selection removes
deleterious mutations
selection for beneficial changes
positive selection
selection against deleterious changes
purifying selection
result of the migration of individuals and movement of gametes between populations
gene flow
movement of one population group into another
gene flow
example of gene flow
new genes into gene pool (pop)
humans expanded their range into range of Neanderthals
results from random changes in allele frequencies
genetic drift
harmful alleles may increase in (blank) and rare advantageous alleles may be (blank)
alleles, lost
in large populations, genetic drift can influence frequencies of alleles that (blank)
do not affect survival and reproduction
in small populations, genetic drift can be
significant
population bottleneck
survival by a few
environmental conditions result in survival of only a few individuals
population bottleneck
genetic drift can reduce (blank) in population
genetic variation
population bottleneck example
hunting and habitat destruction leads to decrease in prairie chicken
colonizing population is unlikely to have all the alleles present in whole population
founder effect
occurs when individuals choose mates with particular phenotypes
nonrandom mating
plant example of nonrandom mating
self-fertilization
if individuals choose the same genotype as themselves, (blank) will increase
homozygote frequencies
form of nonrandom mating that favors traits that increase in the chances of reproduction (not survival)
sexual selection
example of sexual selection
traits such as bright colors or long tails may improve ability to compete for mates or to be more attractive to the opposite sex
Sexual selection favors reproduction, but can (blank)
harm survival
Sexual selection may favor traits that enhance an individual’s chances of reproduction but (blank)
reduce its chances of survival
Example of sexual selection improving reproduction
frogs call being signal of survival
mutation
change in nucleotide sequence that effects allele
gene flow
gene from 1 pop to another
genetic drift
random changes in allele within population
nonrandom mating
having preference and driven by sexual selection
5 mechanisms of evolution
natural selection mutation gene flow genetic drift nonrandom mating
Evolutionary change can be measured by (blank)
allele and genotype frequencies
allele frequency equation
p = number of copies of the allele in the population / total number of copies of all alleles in population
If there is only one allele at a locus, its frequency = (blank) and the population is monomorphic at that locus meaning the allele is (blank)
1
fixed
p + q =
1
q =
1-p
allele frequencies at each locus and genotype frequencies
genetic structure
measure the amount of genetic variation in a population
allele frequencies
show how a population’s genetic variation is distributed among its members
genotype frequencies
How genetic structure of a population changes over time is (blank)
a measure of evolutionary change
If (blank) occurs, the genetic structure of a population does not change over time
certain conditions are met
Hardy-Weinberg equilibrium
describes a model situation in which allele frequencies do not change
Genotype frequencies can be predicted from (blank)
allele frequencies
Conditions that must be met for Hardy-Weinberg equilibrium
- no mutation
- no selection among genotypes
- no gene flow
- population size is infinite (no genetic drift)
- mating is random
If conditions of Hardy-Weiberg occur…
-allele frequencies remain constant
-after one generation, genotype frequencies occur in these proportions
AA, Aa, aa
p2 +2pq +q2 = 1
Deviations from Hardy-Weinberg show (blank)
occurrences of evolution
What is Hardy-Weinberg useful for?
-predicting genotype frequencies from allele frequencies
Why is Hardy-Weinberg important?
patterns of deviation from the model help identify mechanisms of evolutionary change
Natural selection acts directly on (blank)
phenotypes
Reproductive contribution of a phenotype to subsequent generations relative to other phenotypes is called
fitness
(blank) of different phenotypes leads to change in allele frequencies
only changes in relative success
fitness of a phenotype is determined by he (blank) of survival and reproduction of individuals with that phenotype
relative rates
Quantitative traits show (blank)
continuous variation
many traits are influenced by alleles at more than one locus and show (blank) variation
quantitative
Distribution of body size in a population is likely to resemble a (blank)
bell-shaped curve
Natural selection can act on traits with quantitative variation in 3 ways:
- Stabilizing selection
- Directional selection
- Disruptive selection
Stabilizing selection
preserves average phenotype
Directional selection
favors individuals that vary in one direction
Disruptive selection
favors individuals that vary in both directions from the mean
Stabilizing selection- graph
reduces variation, does not change mean
Directional selection- graph
individuals at one extreme; more successful
increase in allele frequencies for favored phenotype
Example of stabilizing selection
birth weight
Example of directional selection
Texas longhorn cattle
Example of disruptive selection
black bellied seed cracker birds (bill size)
Disruptive selection- graph
individuals at either extreme more successful than average ones; increases variation in population
-not centered on mean
an allele that does not affect fitness
neutral allele
which alleles tend to accumulate in a population?
neutral alleles
Molecular techniques
identify neutral alleles
study divergence of pops and species
Sexual recombination amplifies the (blank)
number of possible genotypes
Sexual reproduction results in (blank) through the combination of gametes, crossing over, and independent assortment
new combinations of genes
Sexual recombination produces (blank) that increases (blank)
genetic variety
evolutionary potential
disadvantages of sexual reproduction
- recombination can break up adaptive gene combinations
- rate at which females pass genes to offspring is reduced
- dividing offspring into genders reduces overall reproductive rate
Key advantages of sexual reproduction
- facilitates repair of damaged DNA
- permits elimination of deleterious mutations
- Sexual recombination generates new combinations of alleles on which natural selection can act
a polymorphism can be maintained when fitness depends on its frequency in the population
frequency-dependent selection
example of frequency-dependent morphism
fish with right vs let leaning jaws eating scales off predators
Environmental variation helps (blank)
preserve genetic variation
Example of environmental variation preserving genetic variation
butterflies live in environment with temp extremes; pop polymorphic for enzyme that influences flight at different temperatures; heterozygotes favoredbecause they can fly over a larger temp range
enzyme that influences flight at different temperatures
phosphoglucose isomerase
Genetic variation within species is maintained in (blank)
geographically distinct populations
Plant species may vary geographically in the chemicals they synthesize for defense- example
populations of white clover produce cyanide and therefore are found in areas that are not frozen often
Europe- clinical variation
Difficulties of theory of evolution
- absense or rarity of transnational varieties
- organs o extreme perfection (eyes)
- instinct
Evidence for a common ancestor
- morphology
- embryology
- rudimentary organs
Morphology
homology exists across life
Embrology
similarity between embryos early in development
