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Name ____________________________________ Date ____________ Period _____
Agents of Evolutionary Change
Raven Ch. 21
Big Idea 1: THE PROCESS OF EVOLUTION DRIVES THE DIVERSITY AND UNITY OF LIFE.
It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is the most adaptable to
change.
― Charles Darwin (1859)
Essential Knowledge:
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Natural selection is a major mechanism of evolution
Natural selection acts on phenotypic variations within populations.
Evolutionary change is also driven by random processes.
Biological evolution is supported by scientific evidence from many disciplines including mathematics
Organisms share many conserved core processes and features that evolved and are widely distributed among
organisms today.
Phylogenetic trees and cladograms are graphical representations (models) of evolutionary history that can be
tested
Speciation and extinction have occurred throughout the Earth’s history.
Speciation may occur when two populations become reproductively isolated from each other.
Populations of organisms continue to evolve.
There are several hypotheses about the origin of life on Earth, each with supporting scientific evidence.
Scientific evidence from many different disciplines supports models of the origin of life.
Populations Evolve!
o
Natural Selection__________________________________________________________
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______________________ results in:
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differential survival
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differential reproductive success
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“survival of the fittest”
who bears more offspring
_______________________ evolve
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__________________ makeup of population changes over time
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favorable traits (_____________________________) become more common
Individuals ___________________ evolve…
Individuals __________________ or ______________________…
Individuals __________________________ or ________________…
Individuals ______________________ evolve…
Individuals are ______________________
___________________________ evolve
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Variation & Natural Selection
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________________________ is the raw material for natural selection
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there have to be _____________________ within population
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some individuals must be __________________ than others
________________________- Survival & Reproductive success
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individuals with one phenotype leave more surviving offspring
Where does Variation come from?
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_______________________
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_________________ changes to _________________
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errors in mitosis & meiosis (cell division)
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environmental damage
_________________
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mixing of alleles
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______________________ of alleles
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new combinations = new phenotypes
spreads variation
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Examples:
new arrangements in every offspring
offspring inherit traits from parent
_____________________________________________________,
_____________________________________________________,
_____________________________________________________,
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How can the alleles within a population change (evolution)?
5 Agents of evolutionary change
1. ___________________________________
2. ___________________________________
3. ___________________________________
4. ___________________________________
5. ___________________________________
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1. Mutation & Variation
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Mutation creates __________________________________
o
Mutation rates in _________________________ are __________________ (1 in 100,000
division)
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But are constantly appearing in _________________________
Mutation changes __________________________________________.
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As a result, may change:
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Protein amino acid sequence
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may change protein _________________________?
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may change protein _________________________?
changes in protein may change __________________ & therefore change __________
2. Gene Flow
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Movement of ___________________ & ____________________ in & out of populations
 seed & pollen distribution by __________________________
 __________________ of animals
1. sub-populations may have different allele frequencies
2. causes _____________________________ across regions
3. ________________________ differences between populations
3. Non-random mating
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______________________________
4. Genetic drift
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Effect of __________________ events
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founder effect
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small group splinters off & starts a new colony
bottleneck
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some factor (disaster) reduces population to small
number & then population recovers & expands again
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5. Natural selection
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Differential ___________________ & _________________ due to changing environmental
conditions
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climate change
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food source availability
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predators, parasites, diseases
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toxins
combinations of _______________________ that provide “_________________” ______________
in the population
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_________________________ evolutionary change
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Measuring Evolution in Populations through Hardy-Weinberg
Raven Ch. 21
Populations & gene pools
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Concepts:
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a ____________________________ is a localized group of ___________________ individuals
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gene pool is collection of ______________________ in the population
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remember difference between alleles & genes!
________________________________ is how common is that allele in the population
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how many _____ vs. _____ in whole population
Evolution of populations
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Evolution = ________________________________________________________________________
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Hypothetical: what conditions would cause allele frequencies to NOT change?
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________________________________________________
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_____________________________ all agents of evolutionary change
1. very large population size (no _______________________________)
2. no migration (no __________________________ in or out)
3. no _____________________________ (no genetic change)
4. _______________________________ (no sexual selection)
5. no ___________________________________ (everyone is equally fit)
Hardy-Weinberg equilibrium
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_____________________________________________________________
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preserves allele frequencies
Serves as a model (________________________ hypothesis)
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natural populations ________________________ in H-W equilibrium
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useful model to ___________________________ if forces are acting on a population
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measuring evolutionary change
Hardy-Weinberg theorem
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Counting _____________________________________
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assume ____________ alleles = _______, _______
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frequency of dominant allele (B) = ________
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frequency of recessive allele (b) = ________
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frequencies must add to 1 (100%), so: _____ + _____ = 1
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Counting ____________________________________ ( _____________________________)
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frequency of ______________________: p x p = _____
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frequency of ______________________: q x q = _____
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frequency of ______________________: (p x q) + (q x p) = ______
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frequencies of all individuals must add to 1 (100%), so: __________________________
H-W formulas:
Alleles:
H-W Problem:
Individuals:
Population: 100 cats, 84 black, 16 white
How many of each genotype?
Must assume population is in H-W equilibrium
Sample Data:
How do you explain the data?
Sample Data:
How do you explain the data?
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Application of H-W principle
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_______________________________
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inherit a mutation in gene coding for _________________________
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oxygen-carrying blood protein
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recessive allele = ___________
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normal allele = ___________
low oxygen levels causes RBC to sickle
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breakdown of RBC
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clogging small blood vessels
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damage to organs
often __________________
Sickle cell frequency
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High frequency of ___________________________
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1 in 5 in Central Africans = HbHs
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unusual for allele with severe detrimental effects in homozygotes
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1 in 100 = HsHs
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usually die before reproductive age
Why is the Hs allele maintained at such high levels in African populations?
Answer:
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In tropical Africa, where malaria is common:
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________________________________ (normal)
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die or reduced reproduction from malaria: HbHb
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die or reduced reproduction from sickle cell anemia: HsHs
________________________________ are relatively free of both: HbHs
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survive & reproduce more, more common in population
Example:
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