Download Evolution Evolution = change in a ______, ______, or

Evolution
Evolution = change in a _________, _____________, or
_________________________ over time
 Populations vary by the __________________________________from one
generation to the next
 Traits are represented by ____________________
 Alleles may modify _____________ (form or structure), _____________, or
_____________
 Evolution = changes in allele frequency over time
2 areas of evolutionary study exist:
1. _____________ describes how populations change from one generation to
the next
 describes how new species originate
 focus is on _____________
2. _____________describes changes in groups of related species
 covers broad periods of time
 determines relationships between species
___________________________: early theory of evolution (1809)
3 important ideas:
1. _______________________: body parts of organisms can develop
with increased usage, while unused parts weaken
2. _______________________: body features acquired during the
lifetime of an organism (muscle bulk) could be passed on to offspring.
THIS IS ________________________!
3. _____________________________: offspring produced with
changes, future generations will be different
Charles Darwin (1860) published “__________________________”; proposed
the idea of _________________________= “Survival of the Fittest”
Darwinism = Natural selection is the driving force
NEO–Darwinism = today’s view, incorporates __________________________
NATURAL SELECTION
 the differences in survival and reproduction among individuals in a
population is due to ________________________________________
 some ________________ provide better traits for coping with the
___________________
 More successful individuals produce ________________
 Superior traits = ________________ increase _____________f
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 Favorable traits are _____________(selection acts _____the trait)
 Unfavorable traits are _____________ (selection acts __________the
trait)
Darwin’s arguments for Natural Selection:
1. _____________________________________________________________
(Darwin calculated that 2 elephants would produce a population of 19 million
after 750 years if all offspring survive!)
2. Population sizes _____________________________
3. ___________________________________________
4. Individuals __________________________________________________
5. There is ___________________among the __________________________
6. Variation is ______________________________
7. Only the ____________________________________________survive
8. Evolution occurs as _____________________________________________
Result = _________________________________________________________
Evidence for evolution does exist and can be observed.
The ________________________by which evolution occurs have been the
cause for debate through the ages!
Other beliefs for the origin of life are not based upon science:
Natural Selection may act upon a population in a variety of ways…
KINDS OF SELECTION:
1. _________________________________ = eliminates individuals that have
___________________________________________
 Individuals with the most common traits are _____________________
 Frequency of common traits is ____________________
 Other trait variations are ____________________________
2. _______________________________= favors traits that are at
_______________________________________________________
 Traits of the opposite extreme are ______________________
 Favored traits become more __________________
 Examples: Insecticide resistance, Industrial Melanism (peppered
moth)
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3. ___________________________ (Diversifying Selection) = occurs when
the environment ________________________________________________
Examples: weeds in Nature are tall, in lawns short
4. _______________________= the differential mating of males (sometimes
females) in a population
 Females choose superior males for mates (_____________________)
 Male Competition: strongest males ___________________
 Leads to _________________________= differences in the
___________________of males and females
 This can lead to disruptive selection
Insert fig 8-1
SOURCES OF VARIATION
 In order for Evolution to occur _____________________________________
 CONSIDERABLE __________________________exists in all populations
 Variation arises from the following mechanisms:
1. _________________________= provide the raw material, can invent
alleles that never existed before
2. _________________________= new combinations of alleles, genetic
recombination
 ________________________– exchange of DNA between non
sister chromatids
 ______________________________of homologous pairs
 Random joining of ____________________
3. ___________________= 2 copies of each chromosome in a cell;
recessive alleles can be hidden
4. ___________________= mating of unrelated partners
5. _____________________________ = maintaining different phenotypes
in a population
 Heterozygote Advantage: _____________________________
 __________________: superior quality of offspring resulting
from 2 different strains of inbred plants
 ____________________________(Minority Advantage): when
the least common phenotypes have the biggest advantage
Not all variation has _____________________________________!
Much is _______________________________ i.e. fingerprints in humans
The ____________________often determines whether a variation is
_____________or whether it has selective value.
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Causes of Changes in Allele Frequencies
 _______________________________was Darwin’s mechanism for evolution
 With the understanding of______________, the picture becomes more clear
 Other factors can change allele frequency other than natural selection
1. __________________________: increase or decrease in allele frequency
due to the impact of the environment
2. __________________________: Introduce new alleles that may provide a
selective advantage; most however are deleterious (harmful)
3. __________________________: alleles introduced by emigration (leave) vs.
immigration (enter)
4. __________________________ : random increase or decrease of alleles;
the effect is strongest in small populations
 __________________________: Occurs when the allele frequencies in a
group of migrating individuals are, by chance, not the same as their
population of origin (Amish & Polydactyly)
 __________________________: occurs when a population undergoes a
dramatic decrease in size; the small group left becomes vulnerable to
genetic drift (environmental catastrophes)
5. __________________________: mates chosen based on particular traits
similar to their own, choose nearby individuals
 __________________________: individuals mate with relatives
 __________________________: females choose males based upon
attractive appearance, behavior etc.
GENETIC EQUILIBRIUM
 Occurs when ______________________________remain constant from
generation to generation
 This is known as _________________________________________
 AT GENETIC EQUILIBIUM THERE IS NO ___________________________!
 In order for this to occur the following conditions must be met:
1. No ______________________________________
2. Mutations _________________________________________
3. The population must be __________________________________ (No
gene flow)
4. The Population is _____________________(No Genetic Drift)
5. Mating is ___________________________
IF ANY OF THESE CONDITIONS IS NOT MET, EVOLUTION
______________________________________!
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Genetic Equilibrium is determined by evaluating the following values:
1. Allele frequencies for each allele (p, q)
2. Frequencies of homozygotes (p2, q2)
3. Frequency of heterozygotes (pq + qp = 2pq)
Also the following two equations hold:
1. p + q = 1 (all alleles sum to 100%)
2. p2 + 2pq + q2 = 1 (all individuals sum to 100%)
Example Problem:
Suppose a plant population consists of 84% plants with red flowers and 16% with
white flowers. The red allele (R) is dominant over the white recessive allele (r).
q2 = 0.16 = White flowered plants (rr trait)
p2 + 2pq = 0.84 = red flowered plants (RR and Rr traits)
To determine the allele frequency of the white flower allele, calculate q by finding
the square root of q2
q = .016 = 0.4
Since p + q = 1, p must equal 0.6
You can also figure out the percentages of individuals with the homozygous
dominant and heterozygous condition
2pq = (2)(0.6)(.4) = 0.48 or 48% = heterozygotes
p = (0.6)(0.6) = 0.36 or 36% = homozygous dominant
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Speciation: the formation of a new species, can occur by way of 3 processes
1. _____________________________________ = a population is divided by
some geographic barrier preventing interbreeding
 Gene frequencies in each population ______________________
 If gene pools diverge enough, interbreeding will not take place if the
barrier is removed
 As a result, _________________________________________
2. ______________________________________ = formation of a new species
without the presence of a geographic barrier
 Balanced Polymorphism: ex. Camouflaged insects
 Hybridization: two distinctly different forms of a species mate and
produce offspring along a geographic boundary; the hybrid eventually
diverges from both parent populations
3. __________________________ = relatively rapid evolution of many species
from a single ancestor (Darwin’s Finches 14 varieties)
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insert fig 8-2
Maintaining Reproductive Isolation: mechanisms at work if no physical barrier
exists
Prezygotic Isolating Mechanisms
- ______________________________________________________________
1. ______________________________: species don’t encounter each other
2. ________________________________: species mate at different seasons
or at different times of the day
3. ____________________________________: when a species does not
recognize a potential mate because it does not perform the correct mating
ritual, display the proper visual signals etc.
4. __________________________________: male and female genitalia are
structurally incompatible
5. ___________________________________: male gametes don’t survive in
the environment of the female gamete
Postzygotic Isolation Mechanisms
- ______________________________________________________________
6. ________________________: zygote fails o develop properly and is aborted
7. _____________________________________: Functional adults but they
are reproductively sterile (mule)
8. ____________________________________: offspring have reduced
viability or fertility
Patterns of Evolution
1. _______________________________: 2 or more species originating from a
common ancestor
2. _______________________________: 2 unrelated species that share
similar traits; occur because each species has independently adapted to
similar ecological conditions (not due to shared ancestry)
3. _______________________________: 2 related species that have made
similar evolutionary changes after their divergence from a common ancestor
4. ___________________________: evolution of one species in response to
another (plants & insects, predator & prey)
5. ___________________________: patterns of evolution occurring over
extended periods of geologic time
 _____________________ gradual accumulation of small changes
 ___________________________________ long periods of “status
quo” followed by short periods of rapid evolution
Insert fig 8-3
Insert fig 8-4
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Evidence for Evolution
1. _____________________________ = similar anatomy in different organisms
• ____________________________ = similar structures shared due to
inheritance from a common ancestor (limb structure)
• _______________________________ = traces of a structure that no
longer serves any useful purpose (hip bones in snakes)
• _________________________________ = similar in purpose but not
derived from a common ancestor (wings in birds vs. insects)
2. ___________________________________= embryos of related organisms
develop in similar ways as embryos (vertebrates - gill pouches)
“_______________________________________”. This means that during
an organisms embryological development they will go through stages that
resemble the stages they went through during their evolutionary
development.
3. _________________________________ = chemical processes (metabolism)
-genetic code, organic compounds, dependence on water
- 98% of DNA is shared between humans and chimps
4. ______________________________: Transitional fossil forms = show
intermediate stages of change (horses)
5. _____________________ provides variation - mutations
6. ________________________________________ can cause change
(Industrial Revolution - Peppered Moth)
7. ______________________________ = bell shaped curve showing variation
in a species , few extremes (rabbit color ranges from light to dark)
• Directional Selection = shift in one direction (dark coats)
• Disruptive Selection = acts on middle of curve (predation of medium
coats)
• Stabilizing Selection = selection against the extremes in stable
conditions
8. _______________________________: unrelated species living in similar
environments but in different geographic areas look alike
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