Download Chapter 16

Chapter 16
For Wednesday, January 31
• Read over chapter 22
• Make sure you Bring text
January 28 Outline
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1.5 Scientific Method
16.3 Darwin Principles
16.5 Individuals do not evolve, populations do
16.6 Mutations
16.7 Directional Selection
16.8 Selection against or in favor of extreme
phenotypes
• 16.9 Maintaining variations in a population
• 16.10 Genetic Drift
• 16.11 Gene flow
1.5 Biological Inquiry
You are normally successful in your studies
but for some reason in one class your
average has slipped.
Q: What series of steps do you carry out to
find the root of the problem?
No simply blaming the professor
is not an option!
1.5 Biological Inquiry
1.
2.
3.
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5.
Research Problem
Hypothesis
Prediction
Experimental Tests
Conclusion
– (confirm or refute the hypothesis)
6. Repeat or revise
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Increased number to trials by peers further
VALIDATES
7. Report test results
1.5 Biological Inquiry
1.
2.
3.
Research Problem
Hypothesis
Prediction
4. Experimental Tests
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Materials
Procedure
o Control group a placebo (1.6) to avoid ???
o Experimental group (1.6)
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Observations and data collection (graphs, charts, table)
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5.
6.
7.
Independent Variable (is the tested
Dependent Variable
Qualitative and Quantitative
Analysis of Data
Conclusion
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(confirm or refute the hypothesis)
Repeat or revise
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Increased number to trials by peers further VALIDATES
Report test results
16.3 Darwin's Inquiry
1. Research Problem:
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Why the echinoderms do not over populate?
2. Hypothesis:
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Nature has checks and balances
3. Prediction:
4. Experimental Tests
• Observations
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Populations have inherent reproductive capacities
No population can survive w/o competition of resources
Analysis of Data
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Darwin's Concept of Competition
5. Conclusion
6. Repeat or revise
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Consistent patterns within his data
7. Report test results (On the Origin of Species)
1.6 Experimental Tests
• Controlled Experiment
• Open ended Experiments
• Field Experimental
– Mimicry
All must avoid inner Biasness
16.3 Darwin Principles
• George Cuvier revolutions
– Missing?
• Jean Lamark
– Inheritance of Acquired Characteristics
• hereditary mechanism by which changes in physiology
acquired over the life of an organism (such as muscle
enlarged through use) are purportedly transmitted to
offspring
– What is incorrect with this???
• Weisman
– Mouse Hater or Scientist??? Disproved Lamark
Lamark’s Giraffes
Darwin
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Cambridge Degree in Theology / Naturalists
1859 The Origin of Species by Means of Natural Selection,
Or The Preservation of Favored Races in the Struggle for
Life
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Charles Darwin devised a theory of evolution based on
variation and natural selection
Included in hid theory were five main ideas:
1. Overpopulation
2. Competition
3. Survival of the Fittest
4. Reproduction
5. Speciation
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This would be Darwin’s View
of Lamark’s giraffes .
16.5 Population Terms
• Morphological: Form
• Physiological: helps the body function in an
environment
– Genotype: Genetic expression on a gene
– Phenotypes: Physical representation of a gene
16.5 Population Terms
• Chromosomes: consist of a single
molecule of DNA, a unit of heredity
• The Gene Pool: all of the genes in a
population
– Genes: genetic traits,
• Eye color
–Alleles: variation of genes,
» Blue, Brown, green, hazel
• Leads to variations in phenotypes
16.5 Five reasons for Variations
Why you are not like your Folks
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2.
3.
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5.
Gene Mutations
• produces new alleles
Crossing over
• New combination of alleles w/i Sperm and egg
• Chromosomes break and exchange information
Independent Assortment:
• Never can predict which chromosomes will pair up
• Sperm and egg
Fertilization
• Combines alleles from two parents
Change in Chromosome Number or Structure
• Loss, duplication, repositioning of genes.
16.6 Mutations Revisited
• Mutation Rate probability between replication
Mutations are random and the phenotypic outcome may
be neutral, beneficial, harmful, or even lethal to the
individual depending on other interactions.
• Neutral, Beneficial, lethal mutations
• Growth rate vs. Collagen
• Rethink Giraffe Neck????
16.6 Mutations Revisited
a. Lethal mutation is an expression of a gene that
results in death.
b. Neutral mutations, whether or not they are
expressed in phenotype, have no effect on
survival and reproduction.
c. Beneficial mutations are those that bestow
survival advantages.
Mutations are the only source of new alleles—the
genetic foundation for biological diversity.
16.6 Mutations Revisited
16.7 Directional Selection
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Alleles frequencies that give rise to a range
of variations in a phenotype tend to shift in a
consistent direction.
– Forms at one end of a Phenotypic range become
more common then midrange forms
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Pesticide Resistance
Antibiotic Resistence
Two forms
– Stabilizing Selection
– Disruptive Selection
Response to change in the environment
THE KEY IS THE ENVIRONMENT
16.7 Directional Selection
• How could any dark morphed pocket mice
survive in the Arizona’s Sonoran Desert ?
Stabilizing Selection Link
Disruptive Selection Link
16.9 Maintaining Variations
in a Population,Sexual dimorphism
• Two different morphologies. male and female
– phenotypes or secondary sexual characteristics.
• Sexual selection is based on any trait that gives the
individual a competitive edge in mating and producing
offspring.
• Many times the males compete for the privilege of
mating with certain females but at other times the
females are the agents of selection when they pick their
mates.
• Through nonrandom mating, alleles for preferred traits
increase.
• This leads to increased sexual dimorphism
16.9 Balanced Polymorphism
• Balanced polymorphism (having many forms) is the
maintenance of two or more forms of a trait in fairly steady
proportions over time.
• This occurs when nonidentical alleles are maintained at
frequencies greater than one percent.
• Malaria
• Sickle-cell anemia
• Heterozygotes HbS/HbA, comprise about one third of the pop
• It is now known that heterozygous individuals are more
resistant to the protozoan that causes malaria.
• They survive in greater numbers than the homozygotes.
16.10 Genetic DriftThe Chance Changes
• The random change in allele frequencies over
time, due to chance occurrences alone.
• More significant in small populations.
– “Easier to spread”
• Sampling error Rule of Probability
– 50 coin flips, 500 flips
– explains why the chance of any given allele becoming more or
less prevalent is more pronounced in a small population.
• Fixation means that one kind of allele remains at
a specified locus in a population.
16.10 Genetic DriftThe Chance Changes
• Genetically modified fruit makes the News
http://www.gmoinfo.ie/papaya.php
16.10 Bottlenecking
Examples of Genetic Drift: elephant seals, cheetahs, humans (amish)
16.10 Bottlenecking
GM papayas Yummy goodness or Destroyer
Of the Human Genome?
Using the key terms from 16.9-16.11
Iiwi pronounced “EEVEE
16.10 Bottlenecking
Iiwi
(Vestiaria coccinea)
'I'iwis are some of the most spectacular birds found in the Hawaiian Islands,
with their long, decurved bills and striking red and black feathers. This
species is still relatively common in high-elevation forests on the island of
Hawaii, and has smaller populations on four other main islands; but its high
susceptibility to avian malaria could make it extremely vulnerable to the
future introduction of mosquitoes capable of surviving at high elevations.
http://www.audubon2.org/webapp/watchlist/viewSpecies.jsp?id=108
16.11 The flow of Genes
• Q: What is the difference between
Immigration and Emigration?
• A: The Gene Flow: physical flow of alleles
between tow or more populations.
– Immigration: population gains alleles
– Emigration: population loses alleles
16.10 Genetic Drift- The Chance
Changes
• Bottleneck Effect
• This is a severe reduction in population size that
causes pronounced drift.
– Contagious disease, habitat loss, hunting
• For example, the elephant seal population was hunted down
to just 20 individuals.
• Then the population rebounded to 130,000.
• In bottlenecks, some stressful situation greatly
reduces the size of a population leaving a few
(typical or atypical) individuals to reestablish the
population.
The Founder Effect
• Genetic outcomes also can be unpredictable
after a few individuals establish a new
population
– Seedling on birds
– Acorns and Blue Jays
• In the founder effect,
– a few of these original founders had a mutation, the
gene defect would then be passed on to their
descendants for generations to come.
• Amish, cultural isolation
• Selective Inbreeding
• Geographic Isolation????
The Founder Effect
• Genetic outcomes also can be
unpredictable after a few individuals
establish a new population
– Seedling on birds
• It is the effect of drift when a small number of
individuals start a new population.
• By chance, allele frequencies of founders may
not be the same as those in the original
population.
finito