Announcements

1
Announcements

• Lab 3 Information?webpage
• Midterm test Thursday Feb. 24
• Readings http//www.mun.ca/biology/dinnes/B2900/R
  eadings.html
• Summary topics, Example midterm questions
• http//www.mun.ca/biology/d
  innes/B2900/B2900.html
• Thursday Feb. 17 review Answers

2
Studies in Evolution

• Methods of Evolutionary Analysis
• Adaptation (Ch. 9)
• Sex and Sexual Selection (Ch. 7, 10)
• Life-history evolution (Ch. 12)

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3

• 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

4

• 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

5

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

6

• 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

7

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

8

• 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
  

9

• 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

10
Increased life span in Drosophila
Selection for increased life span
Fig. 12.6
Select for early and late reproduction
11

• 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

12

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

13
(a) Wild Type
sum
14
(b) Mutant
sum
15
(c) Mutant
sum
16
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

18

• 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

19
Inbreeding depression andAge
Fig. 12.9
NS acts more weakly on late-acting deleterious
mutations and they will accumulate Evidence Inbr
eeding depression increases with age
20
Trade-off in Reproduction
Fig. 12.13a Collared flycatcher Early
reproduction Smaller clutch size
Breed at age 2
Breed at age 1
21
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
22
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 ?

24

• Selection Thinking
• Natural Selection and Adaptation
• - kin selection social behaviour
• - form and function
• - sex and sexual selection
• - life-history variation

25
Principles of Evolution and Systematics
First Half Topics

• Introduction (Thinking like an evolutionary
  biologist)
• 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
• Tuesday March 1, 2005
• Show times 1030 1145