Evolution Notes from 1-7-13
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Acquired characteristics theory (WRONG) – characteristics acquired or built over a lifetime
passed on
Natural Selection Theory – Charles Darwin(Wrote Origin of Species in 1859 explaining his theory)
o 1st. Organisms tend to produce more offspring that can survive
o 2nd. Natural variation, mutations and gene shuffling
o 3rd. Competition for resources/Struggle for existence
o 4th. Survival of the fittest (who’s best fit to survive)
o 5th. Decent with modification (Change over time)
Environment does not cause change in organisms, variation does. Variation already exists,
whoever is best fit and has the trait, will survive. Ex: Giraffes long necks were favored in their
environment
Adaptation – trait that is helpful to an organism. Those with the best trait outcompete.
o Darwin studied Finches, realized that similar finches adapted different beak shapes
based off different environmental conditions on different island in Galapagos.
Speciation – where one species is completely changed/adapted for environment, new species is
created and makes infertile offspring
Geographic Isolation – same ancestor, then separated into different environment and then
different traits are accumulated based off environments, later they are completely new species
Extinct Organisms – organisms that die out and are no more
Endangered – organisms that are in danger of becoming extinct. They have to mate with exact
same species to produce fertile offspring of same species
Biodiversity – diversity of life
Population Genetics Notes from 1-10-14
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Allele/Gene Frequency – how often you see a gene in a population.
o Bad genes decrease over time and good genes increase
Gene pool – all different types of genes in a population.
o When organisms with “bad” genes die out, those “bad” genes are removed from the
gene pool.
Natural Selection didn’t determine the outcome of a species all the time.
o Genetic Drift Theory – frequency of a certain gene in a population can also be affected
by random chance events. Ex: Natural Disasters can wipe out a species before it
reproduces good genes, or an Elephant sat on the only organism with good genes
before it reproduced and it died.
o Genetic Flow Theory – changing genetic makeup when individuals move from one place
to another. Ex: Uh I don’t have a legit example so…. Ask someone?
Natural Selection, Genetic Drift, and Genetic Flow theories, all can determine the gene pool of a
population
Directional Selection – When one extreme of a trait is favored
Disruptive Selection – When both extremes are favored and average is not
Stabilizing Selection – Neither extreme is favored, average is favored.
Evidence of Evolution Notes from 1-15-14
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Fossil Record – important evidence. We can see in fossil layers that organisms that are similar
are changing. Paleontologists study these fossils
Comparative Anatomy
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Homologous Structures – we all have similar anatomical parts/structures but they
have different functions
o Vestigial Structures – leftover structures from evolution that serve no purpose.
Ex: Whales have hip bones that serve no purpose now. It is said that they had
legs as they are mammals. Humans have tailbones, suggesting we had tails and
that we were once monkeys.
o Embryology – all vertebrates have a similar embryonic stage.
Biochemical – testing DNA of different organisms. All life has same universal code. Finding
differences in amino acid chains.
o The more differences in chains of two organisms means they branched off longer
back
o Cladogram – diagram showing evolutionary relationships
Geographical Distribution – organisms distributed around the world have similar characteristics
o Before the continents drifted apart, a single species is present. When continents
drifted apart, the species evolved differently into new species.
o Convergent Evolution – different species becoming similar based off environmental
pressures
o Divergent Evolution – similar species becoming different
o Parallel Evolution – not becoming similar or different, just evolving together. When
organisms specialize at gathering resources, that trait is favored.
Other Important Information
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Horse Evolution
o Hyracotherium  Mesohippus  Merychippus  Equus
o Over time, habitat changed from forest to plains. Food and resources change,
defense strategies change, shelters change.
o Horses moved from forest to grasslands so over time they adapted to become
larger and stronger, food changed so larger flatter molars developed. Had to be
able to run faster so toes disappeared too hooves and legs became longer and
stronger.
Adapting is not a matter of choice but chance that an organism has a beneficial genetic variation
Variation – a different phenotype for a trait in a species
Mutation – a genetic variation in genetic code
Industrial Melanism – term used to describe the adaptation of an organism in response to
industrial pollution.
The few Black peppered moths in England survived after the trees changed to a darker color due
to pollution. The white peppered moths died since birds could spot them on dark colored trees.
Hardy Weingerburg Equilibrium – G.H Hardy and W. Weinburg stated that if 5 conditions are
met, then the population’s alleles and genotype frequency won’t change (no evolution).
o There are no mutations of alleles
o The breeding population is large
o Mating is random
o There is no immigration or emigration
o There is no natural selection (all genotypes are equally fit for the environment)
I MIGHT NOT HAVE INCLUDED EVERYTHING
-MADHAV