Download honors biology Ch. 13 Notes Evolution

honors biology
Ch. 13 Notes
Evolution
13.1 Briefly summarize the history of evolutionary
thought.
•
Evolution: The development of new types of organisms
from preexisting types over time.
•
Modern definition: a heritable change in the
characteristics within a population from one generation to
the next.
•
Idea as old as ancient Greeks.
Charles Darwin
•
1830, 22 years old
•
Served on H.M.S. Beagle: “Shipʼs Naturalist”
•
Around-the-world voyage lasting five years.
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Aristocrat so could socialize with Captain.
•
Despised by the Shipʼs Surgeon.
•
Sought to provide evidence and mechanism for evolution
13.1 Explain how Darwinʼs voyage on the Beagle
influenced his thinking.
Geology (Rock Strata or layers)
•
Cuvier (anatomist/archeologist)
reassembled fossil bones
o Stated:
o Past organisms differed greatly from any living
species.
o Some organisms had become extinct.
o Deeper, older strata hold fossils that are
increasingly different from living species.
o Catastrophism: sudden geologic catastrophes
caused extinction of large groups of organisms at
certain points in the past. (Geologic change and
extinction occurred).
•
Lyell (geologist)
o Shared some of Cuvierʼs ideas
o Laws of nature in past same as today:
o “Uniformitarianism”
o Lyellʼs geologic evidence fit with Darwinʼs
evidence from biology.
o
Biology
•
Lamarckʼs Ideas on Evolution
o Died the year Darwin set sail.
o Supported change over time.
o Spontaneous generation for simple life.
o Simple life becomes more complex.
o Acquire Traits thru experience or behavior then
pass those traits on to offspring.
o “Inheritance of Acquired Characteristics”
Darwinʼs Competition:
Scientists donʼt argue that evolution occurs, but HOW it
happens or itʼs mechanism.
•
1830-1835 Voyage of the Beagle
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1830 Alfred Russell Wallace turns 7 years old, grows up to
be a biologist and also sails around the world.
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Both Darwin and Wallace arrive at the same conclusions.
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1858 Both present ideas to scientists in London.
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1859 Darwin publishes: “On the Origin of Species”
•
1835  1858 = 23 years
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13.1 Describe the ideas and events that led to Darwinʼs
1859 publication of The Origin of Species.
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13.2 Explain how the work of Thomas Malthus and the
process of artificial selection influenced Darwinʼs
development of the idea of natural selection.
Thomas Malthus: Wrote an essay on human populations:
More individuals are born than can survive to maturity.
Artificial Selection: Selective breeding of animals and crops to
attain traits needed.
13.2 Describe Darwinʼs observations and inferences in
developing the concept of natural selection.
13.2 Explain why individuals cannot evolve and why evolution does not
lead to perfectly adapted organisms.
Individuals do not evolve:
Evolution does not lead to perfectly adapted organisms:
13.3 Describe two examples of natural selection known to occur in nature.
Notes three key points about how natural selection works.
Example #1:
Example #2:
Three Key points:
13.4 Explain how fossils form, noting examples of each process.
Fig. 13.4 A-F
A. Skull of H. erectus: actual remains
B. Ammonite casts: minerals replace organic molecules, harden, refilled,
hardens, turned out of a mold.
Petrified trees.
C. Dinosaur tracks: trace fossils: footprints, burrows, other traces that
represent behavior.
D. Fossilized organic matter of a leaf: actual remains preserved by omitting
bacteria and fungi from growing.
E. Insect in amber: fossilized tree sap
F. Ice Man: frozen
-. La Brea tar pits
-. Peat bogs: Tolund Man
13.4 Explain how the fossil record provides some of the strongest
evidence of evolution.
The Fossil Record: the sequence in which fossils appear within layers of
sedimentary rocks.
✍ Strata: layers
✍ Superposition: oldest is deepest, youngest is shallow
✍ Fossilization is a rare event
o hard parts fossilize best and most often
o soft parts (skin, feathers) fossilize least often.
✍ Speciation requires little time (geologic time scale)
✍ Fossil record is incomplete as one should expect.
✍ Bacteria is oldest fossilized life form
✍ Transitional fossils: fig. 13.4H
o Terrestrial mammals to whales
o Vestigial pelvis
o Share ankle bone design unique to: pigs, hippos cows, camels, and
deer.
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Evidence of Evolution:
✍ Fossils (“Comparing Primate Fossils” Activity)
✍ biogeography
✍ comparative anatomy
o homologous features: Blast Animation
“Homologous Structures”
o analogous features
o embryonic development:

gill slits

tail
o vestigial features
Molecular biology
AA sequence in proteins (“Biochemical Evidence” activity)
Chromosomes (“Comparing Primate Fossils” Activity)
Important molecules: Cytochrome c highly conserved.
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
✍ 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 recently are shared only
within smaller groups of organisms. (Tetrapods all share
basic limb bone structure 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 genes in a population at any one
time. Used to study evolution at the population level.
Population: A group of individuals of the same species living in the
same place at the same time.
Microevolution: Evolution on its smallest scale, occurring in the
gene pool of a population. When the relative frequencies of
alleles in a population change over a number of generations.
13.8 Explain how mutation and sexual recombination produce
genetic variation.
Mutation:
New alleles originate by a change (mutation) in the nucleotide
sequence of DNA.
✍ Ultimate source of genetic variation
✍ Most mutations occur in body cells and are not passed on.
✍ Only mutations in gametes are passed on.
✍ Chromosomal mutations:
o that delete, disrupt or rearrange many gene loci
are usually harmful.
o Duplication of part of a chromosome is an
important source of genetic variation.

Extra genes that can be mutated.

Olfactory receptor genes in mammals
allows for greater range of scent
detection.

Mice = 1,300 receptors

Humans = 1,000 receptors
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Sexual Recombination
Fresh assortments of existing alleles:
✍ Crossing over during Prophase I.
✍ Independent orientation of homologous chromosomes Metaphase I of
meiosis
✍ Random Fertilization
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?
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 rapid reproduction rate.
o Bacteria are haploid, one gene per character, a new allele can have
immediate 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 diploid genomes prevent most mutations from significantly affecting
genetic variation in plants and animals from generation to
generation.
13.9, 10 EXTRA CREDIT: Hardy-Weinberg 3 pts. max.
Do: Objectives 13.9, 10 and
Process of Science: “How Can Frequency of Alleles Be Calculated?” (13.9) See:
“Student Media” on Objective Sheet.
DUE: Submit online for credit before test day.
MECHANISMS OF MICROEVOLUTION
13.11 Define genetic drift and gene flow. Explain how the bottleneck effect
and the founder effect influence microevolution.
Genetic drift: A change in the gene pool of a population due to chance.
✍ The smaller the population, the greater the effect.
✍ Alleles may be lost to the population due to chance
✍ This reduces variation by such losses.
✍ Examples are:
o Bottleneck Effect
o Founder Effect
Bottleneck Effect:
✍ Catastrophe may kill indiscriminately and leave few survivors.
✍ Reduced gene pool variation affects population
✍ Less variation reduces populationʼs fitness
Founder 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 Flow:
✍ Allele frequencies can change as a result of fertile individuals move into or
out of a population.
✍ Gene flow reduces differences between populations.
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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 prairie chicken reduced by agriculture and development from
th
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.
13.12 Explain why natural selection is the only mechanism that leads to
adaptive evolution.
Chance Events:
✍ Genetic drift (bottleneck, founder effects)
✍ gene flow
✍ mutation
Chance + sorting:
o natural selection

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:
✍ most common type
✍ favors intermediate phenotypes
✍ stable environment
✍ conditions reduce 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 extremes..
✍ example: insects exposed to pesticide
disruptive selection:
✍ environmental conditions are varied and favors individuals at both
extremes.
✍ leads to two or more contrasting phenotypes
13.14 Define and compare intrasexual selection and intersexual selection.
Intrasexual selection or within the sex usually between males
✍ “Winner takes all”
✍ Male wins territorial rights to a group of females.
✍ Usually agonistic or ritualized
✍ Example: lions, elk, mountain sheep
Intersexual selection or mate choice
✍ between males and females
✍ Females choose male
✍ 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
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13.16 Explain how genetic variation is maintained in
populations.
Diploidy: 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
Balancing Selection: When natural selection maintains
stable frequencies of two or more phenotypic forms in a popul.
✍ heterozygote advantage:
o homozygotes are selected against
o NN = susceptible to malaria/ nn =
susceptible to sickle-cell
✍ frequency-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 #ʼs 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 non-coding region of DNA
✍ Occurs but doesnʼt change protein significantly
13.17 Give four reasons why natural selection cannot
produce perfection.
1. Selection can act only on existing variations
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 historical 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 compromises
a. Each organism but do many tasks
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
interact.
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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