Download biology Ch. 13 Notes Part b Evolution

biology
Ch. 13 Notes Part b
Evolution
13.6 Explain how evolutionary trees are constructed and used to
represent ancestral relationships.
✍ Darwin was the first to view the history of life as a tree, with
multiple branchings from a common ancestral trunk to the
descendant species at the tips of the twigs.
✍ Fig. 13.6 Evolutionary Tree
http://163.16.28.248/bio/activelearner/17/ch17summary.html
✍ Homologous structures, both anatomical and molecular, can be
used to determine the branching sequence of such a tree.
✍ Genetic Code: (A, T, C, G) is a homology shared by all species
because they date to the deep ancestral past.
✍ Characteristics that evolved more __________ are shared only
within smaller groups of organisms. (Tetrapods all share basic
_____ ______ __________ but their ancestors do not.
THE EVOLUTION OF POPULATIONS
13.7 Define the gene pool, a population, and
microevolution.
Gene Pool: The total collection of ___________________at
any one time. Used to study evolution at the population level.
Population: A group of individuals of _____________species
living in the same _________at the same _________.
Microevolution: Evolution on its _________scale, occurring
in the gene pool of a population. When the relative
frequencies of ________in a population change over a number
of _______.
13.8 Explain how mutation and sexual recombination
produce genetic variation.
Mutation: A chance event, not a mechanism (controlled
by genes.)
New alleles originate by a change (mutation) in the
______________ sequence of DNA.
✍ Ultimate source of genetic variation
✍ Most mutations occur in ______ _______ and are not
passed on.
✍ Only mutations in ____________ are passed on.
✍ C________________ mutations:
✍ that delete, disrupt or rearrange many gene loci are
usually harmful.
✍ Duplication of part of a chromosome is an important
source of genetic variation.
o Extra genes that can be mutated.
o Olfactory receptor genes in mammals allows for
greater range of scent detection.
o Mice = 1,300 receptors
o Humans = 1,000 receptors
Sexual Recombination
Fresh assortments of existing alleles:
✍ C______________ during Prophase I.
✍ I____________________________________ Metaphase I of meiosis
✍ S____________________________
✍ R
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Review Questions:
1. What is the ultimate source of genetic variation?
2. What is the source of most genetic variation in a population that reproduces
sexually?
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1. mutation
2. Unique combinations of alleles resulting from sexual reproduction.
13.8 Explain why prokaryotes can evolve more quickly than eukaryotes.
✍ Prokaryotic mutations can multiply rapidly due to ______ ___________ rate.
Bacteria are _____loid, one gene per character, a new allele can have
___________________ effect.
✍ Mutation Rate:
o Animals and plants average 1/100,000 genes per generation.
o Considered a low mutation rate.
o Long time spans between generations,
o ___ploid genomes prevent most mutations from significantly
affecting genetic variation in plants and animals from generation to
generation.
MECHANISMS OF MICROEVOLUTION
13.11 Define genetic drift and gene flow. Explain how the bottleneck effect and
the founder effect influence microevolution.
Genetic _________: A change in the gene pool of a population due to chance.
✍ The __________ the population, the greater the effect.
✍ Alleles may be ________ to the population due to chance
✍ This __________ variation by such losses.
✍ Examples are:
o B___________ Effect
o F___________ Effect
________________ Effect:
✍ Catastrophe may kill indiscriminately and leave few survivors.
✍ Reduced gene pool variation affects population
✍ Less variation reduces population’s fitness
________________ Effect:
✍ When a few individuals colonize as isolated island or other new habitat.
✍ The smaller the group, the less likely the genetic makeup will represent larger
population they left.
✍ Genetic difference between large pop. and founder pop. is founder effect.
Gene ______:
✍ Allele frequencies can change as a result of ______ individuals move
_____________________a population.
✍ Gene flow reduces _________________ between populations.
✍ Compare to similarities in a closed society like the Amish.
13.11 Explain how genetic bottlenecks threaten the survival of certain
species.
✍ Ice age: Human population estimates 600 breeding individuals at one
time in S. Africa. Genetic variation between individual humans about
30% less than between individual chimpanzees.
✍ Florida panther
✍ African cheetah
✍ Illinois greater _____________________reduced by agriculture and
th
development from millions in 19 C. to 50 individuals in 1993. Flocks
from neighboring states added into Illinois flock. Regained hatching
success from 50% to 90% due to added alleles.
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FOUNDER EFFECT example
• 1814, 15 people founded British
colony, Tristan da Cunha on island in
Atlantic.
• One of the 15 was a het for retinitis
pigmentosa.
• In 1960, of the 240 decendants, 4 had
RP, 9 were hets.
• Frequency 10x higher than parent
population.
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13.12 Explain why natural selection is the only mechanism that leads to
adaptive evolution.
Chance Events:
✍ G____________ (__________+____________)
✍ G________________
✍ M________________
Chance + sorting:
___________ ____________
• chance: random collection of genetic variation
• sorting: some alleles are favored over others.
• sorting makes in adaptive
• improves the match between organisms and their environment.
• environments change
• “fitness” is a moving target
• adaptive evolution dynamic process
13.13 Distinguish between and describe an
example of:
stabilizing selection:
✍ ________ common type
✍ favors _____________ phenotypes
✍ ___________ environment
✍ conditions _________ phenotypic variation
✍ example: human infant weight averages
6.5-9 pounds, extremes have higher infant
mortality.
directional selection:
✍ shifts the overall makeup of the popul. by
selecting against individuals at one of the
phenotypic ___________.
✍ example: insects exposed to __________
disruptive selection:
✍ environmental conditions are varied and
favors individuals at ______________.
✍ leads to________________________
_________ phenotypes.
13.14 Define and compare intrasexual selection and
intersexual selection.
Intrasexual selection or within the sex usually between males
✍ “Winner takes _____”
✍ _____ wins territorial rights to a group of ___________.
✍ Usually ____________or ritualized
✍ Example: lions, elk, mountain sheep
Intersexual selection or mate choice
✍ between ______ and ____________
✍ __________ choose ______
✍ Males display adornments
o plumage
o courtship dance
o song
o “Choose Me!”
o studies show it
relates to overall
male health
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13.15 Explain how antibiotic resistance has evolved.
Discovery Channel video clip
http://wps.aw.com/bc_campbell_concepts_6/83/21320/545806
3.cw/index.html
13.16 Explain how genetic variation is maintained in
populations.
___ploidy: having two sets of chromosomes
✍ helps to prevent populations from becoming
genetically uniform.
✍ Recessive alleles hide from selection forces as Hets
✍ Maintains presence of recessive alleles in gene pool
_________ Selection: When natural selection maintains
stable frequencies of two or more phenotypic forms in a popul.
✍ ________zygote advantage:
o homozygotes are selected against
o NN = susceptible to malaria/ nn = susceptible to sickle-cell
✍ ________-dependant selection: most common phenotype selected against
o scale-eating fish in Lake Tanganika, Africa
o attack other fish from behind to steal scales
o right-mouthed/left-mouthed
o easier to defend against most common attacker
o those numbers go down from lack of food
o less common #’s go up from greater food
13.16 Explain what is meant by neutral variation.
✍ Mutations that have no effect, + or -, on the individual
✍ Mutation occurs in __________ region of DNA
✍ Occurs but doesn’t change ___________ significantly
13.17 Give four reasons why natural selection cannot produce perfection.
1. Selection can act only on ____________ ____________.
a. can use only phenotypes available
b. may not be ideal trait for environment
c. advantageous alleles do not arise on demand
d. extinction happens
2. Evolution is limited by _____________ constraints.
a. co-opts existing structures and adapts them to new situations
b. Example: environmental changes favor flight; wings would be best but nature must use the parts available.
Bats and birds did not evolve a new set of appendages, they changed what they already had.
3. Adaptations are often _______________
a. Each organism must do many different tasks but..
b. …adaptations may be better suited for some tasks than others
c. Example: blue-footed booby uses webbed feet to swim after prey well, but they are clumsy on land.
4. Chance, natural selection, and the environment ____________.
a. Chance plays a bigger role than once thought.
b. Example: a storm blows insects out to sea. A few land on an island, many perish. The few that survived may
not be the individuals that would be best adapted to the new environment.
Question: Humans owe much of their physical versatility and athleticism to their flexible limbs and joints. But we
are prone to sprains, torn ligaments, and dislocations.
a. Which one of the four reasons given for why natural selection cannot produce perfect organisms best explains
this?
b. Explain how your chosen reason applies specifically to humans.
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