UST Evolution


Terms in this set (...)

proximate cause
event which is closest to or immediately responsible for some observe results (like mutations caused said phenotype)
ultimate (distal) cause
the 'real' reason something occurred (like variations in a population were present, but certain ones were favored and those individuals survived and reproduced offspring with similar phenotypes)
Darwin's main point
1. some forms are better adapted then others (variability)
2. some forms are better adapted will leave more offsrping and thus increase in frequency in the population (adaptation and reproductive fitness)
3. As environments change through time some new form may become better adapted and increase in frequency - thus new species may form (Natural Selection).
Evidence of evolution
homology, microevolution, experimental evolution, transitions/missing links
importance of cambrian explosion
all body plans except for 1 phyla were genetically laid down in this 40 million year period
study of likeness
shows common ancestry
example: pentadactyl tetrapods or globin proteins
change on a population level
example: peppered moths
experimental evolution
also artificial selection
the most desirable characterisitics are chosen
-change is allele/character frequency in a population between generations
(individuals do not evolve)
-it may not be a reflection of current conditions, but conditions that were causing selective pressure at some point
transition/missing link
part of macro-evolution
rare because fossils are only found in cold, dry, or ice (where they can make an impressions)
a trait that allows an organism to survive and reproduce
oldest population
australian aboriginese ~60k years ago

neanderthal went extinct about 35k years ago
peter and rosemary 30 year test (finches)
studied finches continuously for over 30 years (from 1973)

incredible amount of variability in beak size and shape

beak is food gathering tool, has biggest influence on reproductive fitness
4 testable postulates
1. individuals within a species are variable
2. some of this variability is passed on to offspring
3. more offspring are produced than can survive
4. survival and reproduction are not random.
change depends on two things
changes in external environment

variability inherent in a population
Important thing about evolution
natural selections happens to individuals, but populations evolve
what do we call change between generations?
descent with modificatio
Hamilton's relatedness coefficient
What causes variability
unequal crossing over, overprinting, reverse transcription and insertion, chromosome inversion, polyploidy, duplicate sequence
wobble position
the variable third base in the codon, it protects against mutations in the coding regions of our DNA
C to T or A to G (purine changes to the other purine)
anything that isn't a transition
Crossing over
occurs during meiosis, can result in new combinations of genes on the same chromosomes
point mutations that produce new start codons and new reading frames

ex. polyomavirus - oncogenic - merkel cell cancer. produce at least four different transcripts that differ in binding domains

important in plant virus evolution
reverse transcription and insertion
Adh in drosophila
mRNA of an Adh gene gets reverse transcribed
cDNA inserted into a new chromosom ewithout the intron that it started with.
chromosome inversion
-breaking and re-annealing
-drosophila subobscura
native to Europe, n Africa, middle east
-population spread has gone northward all the way to southern Canada
-develops same clinal frequencies as old world populations within 10 years
-higher latitude in north or south America, frequency of inversion increases
-among angiosperms, the phenomenon of polyploidy (doubling of diploid number of chromosomes) is responsible for about 50% of speciation events
-polyploidy + tendency of plants to hybridize with closely related subspecies = lots of diversity
-polyploidy can happen in earthworms/flatworms
generally happens only in individuals that can self fertilize
can happen in some shrimp and salamanders
-about 2 in every 100000 plants are tetraploid and started as diploid
point mutation
base pair substitutions in NA sequences
gene duplication
duplication of a short stretch of DNA, creating an extra copy of the sequence. Happens during crossingover
-a freely interbreeding group of individuals
-aren't necessarily geographically contiguous.
-If there is gene flow then it is a population. If things get isolated long enough they can become their own species
gene pool
the sum total off genetic information present in a population at any given point in time
a morphological, physiological, biochemical, or behavioral characteristics of an individual organism
the genetic constitution of an indivdual organism
a site on a chromosome, or the gene that occupies the site
a nucleic acid sequence that encodes a product with a distinct function in the organism
a particular form of a gene
gene (allele) frequency
the relative proportion of a particular allele at a single locus in a population (a number between 0 and 1)
genotype frequency
the relative proportion of a particular genotype in a population (a number between 0 and 1)
defined wither with respect t o a genotype or a phenotype in a given environment
average contribution to the gene pool of the next generation made by an average individual of a particular genotype or phenotype
natural selection
-the frequencies of the alleles will change across generations
the alleles with higher fitness become more common
-natural selection acts on individuals
-its consequences are at the population level
-individuals live or die. they reproduce or dont
-the real consequence of natural selection is at the population level
-natural selection acts on phenotypes
-evolution consists of changes in genotypes
-changes in allele frequencies between generations resulting from natural selection effect on individuals. Acts on the individuals that compose a phenotype. When there are exceptions to that is what may shift science and perspective.
individual fitness...
happens through a particular phenotype
phenotypes are affected by:
developmental environment, genes, and environment
absolute fitness
relative fitness
inclusive fitness
kin selection
fitness landscapes
Hardy-Weinberg assumptions
1. large breeding population
2. random mating
3. no mutation
4. no immigration or emigration
5. no natural selction
four uses for Hardy Weinberg
1.Enables us to compute genotype frequencies from generation to generation, even with selection.
2. Serves as a null model in tests for natural selection, nonrandom mating, etc., by comparing observed to expected genotype frequencies.
3. Forensic analysis.
4. Expected heterozygosity provides a useful means of summarizing the molecular genetic diversity in natural populations.
modes of natural selection
stabilizing, disruptive, directional
heterozygote advatange
Also known as OVERDOMINANCE or HETEROSIS, results in a stable, polymorphic equilibrium.
varying selection
If selection varies spatially or temporally, polymorphism may be maintained
frequency-dependent selection
the fitness of the genotype depends on its frequency in the population. If common genotypes have low fitness, then the polymorphism will be maintained.
negative frequency dependent selection
maintains an approximately equal amount of right- and left-mouthed fish.
positive frequency dependent selection
in which it is best to to be average - the extreme is selected against
types of frequency-dependent selection
positive, negative, predator-prey, parasite-host, mimicry
gene flow
-occurs between two populations
distribution of alleles within each of those populations is similar
-describes the transfer of alleles between populations
genetic drift
--fluctuations in allele frequencies in a population because of chance events
-natural disasters, accidents, similar
founder effect
-establishment of a subpopulation from a large parent population
-allele frequency and genetic character of the offspring of the subgroup can differ significantly from the parent population
bottleneck effect
-rapid elimination of alleles
-rapid decrease in population size
smaller population
-huge amplitude of changes in allele frequencies
-more subject to effects of genetic drift
large population
some alleles increase over time or become fixed and some decrease, but they're not lost the way they are in small populations