Principles of Evolution and Systematics Feb' 12 Happy Birthday

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Principles of Evolutionand SystematicsFeb. 12
(Happy Birthday!!!)

• Midterm Test Thursday Feb. 19, 2004
• Sample test on Webpage
• Lab 3 (Monday) Check Web Page

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Sexual Selection

• Chapter 10

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• Sexual Selection

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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• Sexual Selection

Dr. Ian Jones (Biology) Sexual selection in
Auklets
Aethia pygmaea I. Jones
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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 Diversity
• Mammals
• Mice mature early, reproduce quickly
• Bears mature late, reproduce slowly
• Plants
• annuals live 1 year then die
• perennials live gt 1 year
• Bivalves
• oyster 20 million eggs (0.05 mm)
• clam 100 eggs (0.30 mm)

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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
• Organisms cant
• - mature at birth
• - produce high-quality offspring
• in large
  numbers
• - live forever
• Energy available for each activity finite
• trade-offs

and
and
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• Life History Evolution

Pattern of Energy
Allocation Opossum Life-History
Fig. 12.2
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Mussel life history
Spat
Settlement
Planktonic larvae
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• Life History Evolution
• Environmental variation the source of much of the
  observed life history variation
• Questions
• 1. Why do organisms age and die ?
• 2. How many offspring should be produced
  ?
• 3. How big should each offspring be ?

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Reproduction and Aging (senescence)
Fig. 12.4
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• 1.Why do organisms age and die ?
• Aging (senescence)
• late-life decline in fertility and
  survival
• Aging reduces fitness and should be opposed by
  natural selection
• M. R. Rose (1991) Evolutionary Biology of
  Aging

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• Theories of Aging and Senescence
• Rate-of-living theory
• Evolutionary theory

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• Theories of Aging and senescence
• 1. Rate-of-living theory
• aging due to the accumulation of
  irreparable damage to cells and tissues
• (Prediction high metabolic
  rate shorter life span)
• lack of genetic variation for selection
  against aging
• (Prediction selection can
  not lengthen life-span)

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• Theories of Aging and senescence
• Rate-of-living theory
• Prediction high metabolic rate shorter life span
• all species should expend about the same amount
  of energy per gram of tissue per lifetime
• - slowly over a long lifetime
• or - rapidly over a short lifetime
  

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Fig. 12.5
Great variation
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• Theories of Aging and Senescence
• Great Variation in metabolic rate among
  mammals
• - elephant shrew (36 kcal/g/per lifetime)
• - bat (1,102 kcal/g/per lifetime)
• Marsupials significantly lower metabolic rates
  and
• significantly lower life spans
• Variation in rate of living cannot explain
  variation in aging

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Increased life span in Drosophila
Selection for increased life span
Fig. 12.6
Select for early and late reproduction
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• Theories of Aging and Senescence
• 2. Evolutionary Theory of Aging
• aging caused by failure to repair cell and
  tissue damage
• Accumulation of deleterious mutations
• Trade-offs between repair and reproduction

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• Evolutionary Theory of Aging
• Simple Genetic Model (Fig. 12.9)
• (a) Wildtype matures at age 3 dies at age 16
• (b) Mutation death at age 14
• (c) Mutation matures at age 2 death at age 10

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(a) Wild Type
sum
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(b) Mutant
sum
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(c) Mutant
sum
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Fig. 12.9a
1
0.640
area
0.317
0.079
(b) 2.419 0.079 2.340
(c) 2.419 (0.0790.317) 0.640 2.663
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• Evolutionary Theory of Aging
• Fig. 12.9
  Lifetime Repro.
• 
  Success
• (a) Wildtype
  2.419
• (b) Mutation earlier death 2.340
• (c) Mutation trade-off early 2.663
• reproduction and early death

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• Evolutionary Theory of Aging
• Interpretation
• 1. deleterious mutations with effects late in
• life only weakly selected against
• 2. Mutations with benefits early in life and
• deleterious late in life favoured
• (antagonistic pleiotropy)
• trade-off between early reproduction and
  survival late in life

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Inbreeding depression andAge
Fig. 12.9
NS acts more weakly on late-acting deleterious
mutations Inbreeding depression increases with age
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Trade-off in Reproduction
Fig. 12.13a Collared flycatcher Early
reproduction Smaller clutch size
Breed at age 2
Breed at age 1
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Trade-off in Reproduction
Extra eggs
Female given extra eggs show a decline in clutch
size
Control
Increased reproduction early in life ? decreased
reproduction later in life
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Trade-off between energy for reproduction and
later survival in plants
Pairs of closely related species Annual gt than
perennial
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• Evolutionary Theory of Aging
• ETA can explain variation in life history
• Strength of Natural Selection declines
  late in life
• Question
• What is the relative importance of
  deleterious mutations and trade-offs in the
  evolution of senescence ?

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• 2. How many offspring to produce?
• Trade-off fixed amount of energy and time
• the more offspring produced,
• the less time and energy to devote to
• each one

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• Clutch Size in Birds
• (David Lack, 1947)

Selection will favor the clutch size that
produces the most surviving offspring Assumption
probability of offspring survival decreases
with increasing clutch size (Fig. 12.16)
(the more kids, the less food for each)
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Clutch SizeFig. 12.16
Prob. of surviving (P) 0.5
of surviving offspring (CS x P) 5 x 0.5 2.5
Intermediate optimum
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Great tits (Parus major)
young surviving per clutch greater than average
clutch size
8.53
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Clutch Size

• Clutch size lt surviving per clutch
• Birds producing fewer eggs than
• optimum ?
• Other costs
• - trade-off between parents
• reproduction and survival
• - large clutch size may impose other
• costs than just survival ? next

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Fig. 12.18
Daughters clutch size
Eggs removed
Eggs added
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Clutch Size

• Trade-off between offspring quality and quantity

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• 3. How big should each offspring be?
• Trade-off fixed amount of energy
• - many small offspring or
• - few large offspring
• Size number trade-off

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Fish Fruit
flies
Fig. 12.21
Clutch Size
Egg Size
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Fig. 12.22
Number 10/size
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Fig. 12.22
Survival 1- (1/size)
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Fig. 12.22
Parental Fitness Number x survival
1.6 2 x .8
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• Offspring Size
• Conflict of interest between parents and
  offspring
• Parents
• - selection can favour smaller offspring
  than optimal for offspring survival
• Balance between offspring size and survival
• Optimum varies with environment

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• Life History Evolution

Summary Aging and Senescence trade-off
between reproduction and repair Offspring
number trade-off between clutch size and
offspring survival Offspring size
trade-off between offspring size and number
trade-off between offspring size and survival
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Principles of Evolution and Systematics
First Half Topics

• Introduction (Evolution thinking)
• The evidence for evolution (Relatedness of life
  forms)
• Darwin Natural selection (Galapagos Finches )
• Population Quantitative genetics (Genes in
  populations)
• Natural selection Adaptation (Form and
  function
• 
  Sexual
  selection)
• Adaptation and Diversity

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• Coming Next
• The History of Life
• (in 12 lectures)
• Narrated by Dr. Ted Miller
• Thursday Feb. 26, 2004
• Show times 1030 1145