Office Hours

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Office Hours

• Office SN-4114
• Monday, Tuesday, Wednesday 1100 1200
• or by appointment
• Midterm test Thursday Feb. 23

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Biology 2900 Review

• Evolution
• a change over time of the proportions of
  individual organisms differing genetically in one
  or more traits

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• The study of Evolution
• - how populations change
• - formation of new species
• Study of Adaptation and Diversity

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• Evolutionary Biology
• - Where do living things come from ?
• - Why are there so many different kinds of
  organisms ?
• - How have organisms adapted so well to their
  environment ?

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Topics

• Evidence for evolution
• Natural Selection
• Mutation and Genetic variation
• Population Genetics
• Quantitative Genetics (natural selection, modes
  of selection)
• Kin Selection
• Methods of Evolutionary Analysis (Adaptation)
• Evolution of Sex
• Sexual Selection
• Life History Evolution

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• The Fact of Evolution
• - evidence from biology and geology
• - species have changed through time
• - descended with modification from common
  ancestors

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• The Fact of Evolution
• Evidence
• 1. relatedness of life forms
• 2. change through time
• 3. age of the earth

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Natural Selection

• The Theory of Evolution by Natural Selection
  proposes that evolution is the logical outcome of
  4 postulates

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• Evolution by Natural Selection
• 1. Individuals within populations variable
• 2. Some variations inherited by offspring
• 3. Some individuals more successful at surviving
  and reproducing than others
• 4. Survival and reproduction not random tied to
  the variation among individuals

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• Implications and consequences of NS
• -natural mechanism for evolution
• -descent from common ancestor ? order
• -natural classification ? hierarchical
• -all living things related ? phylogeny
• -humans evolved
• Darwin-Wallace Theory of NS testable

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• Test of 4 postulates
• Geospiza fortis on the island of
• Daphne major
• 1. Are populations variable ?
• 2. Variation heritable ?
• 3. Only some offspring live to reproduce ?
• 4. Survival and reproduction nonrandom ?

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Mutation and Genetic Variation Chapter 4

• Mutations are the raw material of evolution
• Mutation?genetic variation?natural selection
• 
  Evolution

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• Genes in Populations
• Questions
• How much genetic diversity exists in natural
  populations ?
• What determines the level and pattern of genetic
  variation ?
• What role does natural selection play?

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• Population genetics
• - gene pool
• - deme (population)
• - panmictic unit (random mating)
• quantify genetic variation
• allele freq. ( p, q)
• HWE genotype freq.
• AA Aa aa
• p2 2pq q2

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Hardy-Weinberg Theorem
Chapter 5

• Null model
• Allele and genotype frequencies will not change
  across generations (equilibrium)
• Assuming - random mating
• - large population size
• - no selection
• - no migration
• - no mutation

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Relax Assumptions

• Processes that can change allele and/or genotype
  frequencies
• - Mutation
• - Migration
• - Non-random mating
• - Finite population size
• - Selection ? differential survival,
• fecundity etc. among genotypes

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Maintenance of Genetic Variation

• Balance of gain and loss of alleles
• - balance of forward and reverse mutation
• - selection - mutation balance
• - selection - migration balance
• - heterozygote advantage
• - frequency-dependent selection

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Phenotypic Variation
Most traits controlled by many loci Phenotype
Genotype Environment Continuous
variation Selection acts on the whole phenotype

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Narrow- SenseHeritability ( h2)
VG VA VD VA additive genetic
variation VD dominance genetic variation h2

VA
VA
VP
VA VD VE
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Response to Selection
R h2 S S selection
differential Xs - Xpop R response t
generation Xt1 - Xt

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Modes of Selection

• Mean Variance
• Directional , - -
• Stabilizing 0 -
• Disruptive 0

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Kin Selection and Social Behaviour

• (W.D. Hamilton, Robert Trivers,
• Richard Dawkins)
• Kin Selection
• Inclusive Fitness direct fitness indirect
  fitness
• (personal)
  (relatives)

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Kin Selection and Social Behaviour

• Allele for altruistic behaviour will spread if
• B r C gt 0
• B benefit to recipient
• r relationship between actor and recipient
• C cost to actor
• (B C units of surviving
  offspring)
• JBS Haldane said that he would
  cheerfully
• sacrifice his life for two
  brothers or eight cousins

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Methods of Evolutionary Analysis

• Ask interesting questions
• Answer with
• Observations from nature
• Controlled Experiments
• - laboratory
• - nature

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Adaptations

• Adaptation a trait, or suite of traits, that
  increases the fitness of its possessor
• Evolutionary Biology demonstrate the evolution
  of adaptation through natural selection

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Adaptations

• Adaptive significance of some traits obvious
• Other traits less obvious
• (understanding the adaptive significance
• requires more effort)

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Testing Hypotheses for Adaptations

• Evolution of long necks in giraffes
• Phenotypic plasticity in Daphnia

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• The Adaptive Significance of Sex
• Searching for a mate
• - takes time and energy
• - increases risk of predation
• Mating increases exposure to STDs
• Mate may be infertile
• Cost of producing males
• Why not reproduce asexually ?

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Sex and Evolution

• Advantages of sex
• Remove deleterious mutations (genetic load)
• Genetic diversity in a changing environment (red
  queen)

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Variation in Sexual Reproduction

• Separate sexes - dioecious (plants)
• - gonochoristic
  (animals)
• Co-sexual hermaphroditic
• (malefemale)

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Evolutionary Questions

• Under what condition expect evolution of
• - hermaphroditism versus dioecy

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• Sexual Selection
• (explains sexual dimorphism etc.)

Summary 1. Differences among individuals at
getting mates 2. Asymmetry in limits to
reproductive success - females
of eggs - males of
matings 3. Male competition, female choice
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• Sexual Selection

Summary 4. Reversed when males invest more than
females ( male parental care pipe
fish) 5. Principles of sexual selection in
animals can be applied to flowering plants
Books
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• Life History Evolution
• Evolution by natural selection has modified all
  organisms for one ultimate task
• to reproduce
• (sexual selection one aspect)
• How organisms carry out this task enormously
  diverse

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• Life History Evolution
• Attempts to explain the diversity of
  reproductive strategies
• Trade-offs constrain the evolution of adaptations
• Balance costs and benefits to maximize
  reproductive success

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• Life History Evolution
• Environmental variation the source of much of the
  observed life history variation
• Question
• Why do organisms age and die ?

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• Life History Evolution

Summary Aging and Senescence -
accumulation of deleterious mutations -
trade-off between reproduction and repair
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Topics

• Evidence for evolution
• Natural Selection
• Mutation and Genetic variation
• Population Genetics
• Quantitative Genetics (natural selection, modes
  of selection)
• Kin Selection
• Methods of Evolutionary Analysis (Adaptation)
• Evolution of Sex
• Sexual Selection
• Life History Evolution

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Announcements

• Midterm test Thursday Feb. 23
• Example Questions
• http//www.mun.ca/biology/dinnes/B2900/B2900.html
• Readings http//www.mun.ca/biology/dinnes/B2900/R
  eadings.html
• Lab. 5 Information and Questions on web
  page