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Evolution
By: Dayne Michael, Ari Argoud,
Torrey Donovan, Sara Atun, and
Miranda Katz
Vocab Review
• Scientific Theory: an explanation of natural phenomenon
supported by a large body of scientific evidence obtained
from many different investigations and observations
• Evolution: a gradual change in species (populations) through
adaptations over time
• Natural Selection: process by which individuals that are better
suited for their environment survive and reproduce most
successfully (also called survival of the fittest)
• Speciation: a process of producing two individual species from
one
-member of the population no longer interbred within
their natural environment
3 Types of Natural Selection
• Natural Selection is a mechanism for change in a population and is
responsible for most evolutionary change by selectively changing genetic
variation through differentiated survival and reproduction; goal is to be
“fit enough”
1. Stabilizing Selection:
2. Directional Selection:
3 Types of Natural Selection Continued
3. Disruptive Selection:
Evidence for Evolution
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Structural Adaptations
Physiological Adaptations
Fossils
Anatomy
-a vestigial structure does not have current function but may
have been useful to an ancestor
• Embryology
• Biochemistry
-comparing DNA and RNA
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How Do We Know What Happened When?
1. Radiometric Dating relies on half-life decay of
radioactive elements to allow scientists to date rocks
and materials directly
2. Statigraphy provides a sequence of events from
which relative dates can be extrapolated.
3. Molecular clocks allow scientists to use the
amount of genetic divergence between organisms to
extrapolate backwards to estimate dates.
Easy way to memorize:
V= variation
I=inheritance
S=selection
T=time
Review of Evolution of Populations
• Sources of genetic variation: mutations and
genetic shuffling.
• Genetic drift: random change in allele
frequency
• Founder effect: changes in allele frequency as
a result of the migration of a small group of a
population
Population Genetics
• 5 factors affecting gene pools
• 1. Non-random mating
• 2. Gene flow: immigration and emigration (the flow of
genes entering or leaving a population)
• 3. Mutations
• 4. Genetic Drift: changes in allele frequency by chance
events
• 5. Natural selection acting on a phenotype variation
Population Genetics Continued
• Changes in Genetic Equilibrium
• A population in genetic equilibrium is not
evolving. Both alleles and phenotypes remain
the same.
• Any factor that affects the genes in a gene
pool can change allele frequencies and shift
the genetic equilibrium
Patterns of Evolution
• A. Divergent evolution: when species that were once
similar diverge (become more and more different)
• B. Adaptive evolution: when one species evolves into
an array of different species to fit different environmental
habitats
• C. Convergent evolution: when species that were
unrelated evolve similar characteristics
Why Natural Selection Acts on the
Phenotype Rather Than the Genotype of
an Organism
• Natural selection acts on the phenotype of an
organism because the organisms with the best
phenotypes are the ones that survive to pass
their genes on to their offspring. Then, that
trait can eventually take over the entire
population.
Review Questions
What is Evolution?
a) A change over time of a certain species
b) Collected observations and evidence of a species
c) Characteristics of a certain species
Darwin’s theory of evolution included all of the following concepts except
a) Individual organisms differ
b) Some variation in organisms is heritable
c) All organisms of the same species inherit the same traits
Structures that have different mature forms that develop from the same embryonic tissue are called:
a) Vestigial organs
b) Homologous structures
c) Embryonic appendages
Individuals that are better suited to their environment, that is- with adaptations that enable fitness, survive and reproduce
most successfully is an example of:
a) Struggle for existence
b) Fitness adaptation
c) Survival of the fittest
What is “On the Origin of Species”
a) A publication by Charles Darwin
b) Descent of Modification
c) Tendency towards perfection
Review Questions Continued
Which of the following is not evidence of evolution
a) Fossil records
b) Geographic distribution of living species
c) The struggle for existence
Which of the following is a source of genetic variation
a) Mutations
b) Fitness
c) Talents
Random change in allele frequency of a population is called
a) The founder effect
b) Genetic drift
c) Mutations
What is not a factor affecting the gene pool
a) Non random mating
b) Gene flow
c) Relative frequency
The kaibab squirrel evolved from the abert squirrel. The kaibab squirrels were isolated from the
main population by the Colorado river. This is an example of:
a) Behavorial isolation
b) Geographic isolation
c) Temporal isolation
Answers
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1-a
2-c
3-b
4-c
5-a
6-c
7-a
8-b
9-c
10 - b