Charles Robert Darwin (1809-1882)

1
Charles Robert Darwin (1809-1882)
2
Charles Darwin and the Voyage of the Beagle
3
Charles Darwin and the Voyage of the Beagle
4
Charles Darwin and the Voyage of the Beagle
5
Charles Darwin and the Voyage of the Beagle

• During the voyage, Darwin...
• was perennially seasick
• read Lyells Principles of Geology
• spent lots of time ashore in South America and
  other locations
• observed and collected a large number of fossils,
  plants, and animals
• What Darwin Saw...
• an earthquake that changed the level of the land
  dramatically in Concepcion, Chile
• fossils of marine shells at 14,000 feet in the
  Andes
• patterns of geographic distribution of plants and
  animals that suggested the importance of
  geographic isolation in the formation of
  species...

6
Charles Darwin and the Voyage of the Beagle

• What Darwin Saw
• Plants and animals in the New World tropics are
  like those in the New World temperate zone, not
  like those in the Old World tropics.
• Extant South American plants and animals are like
  extinct South American plants and animals, not
  like extant plants and animals elsewhere.
• Extant mammals in Australia are not like mammals
  anywhere else.
• Animals (and plants) on oceanic islands are like
  those of the nearest continent, not like those on
  other oceanic islands elsewhere.
• Animals on islands near each other in
  archipelagoes are distinct but similar.

7
(No Transcript)
8
Charles Darwin and Natural Selection

• Darwin wrote two essays, the first in 1842, and
  an expanded version in 1844
• The 1844 essay (it was 240 pages) contains a
  complete, detailed, and well documented argument
  for how the process of natural selection acts to
  produce adaptation or design in organic beings
• Darwin knew what he had done, and showed none but
  his wife and a few close colleagues his essay...

9
Darwin in 1854
10
Charles Darwin and Natural Selection

• We see these beautiful co-adaptations most
  plainly in the woodpecker and misseltoe and only
  a little less plainly in the humblest parasite
  that clings to the hairs of a quadruped or the
  feathers of a bird in the structure of the
  beetle which dives through the water in the
  plumed seed which is wafted by the gentlest
  breeze in short, we see beautiful adaptations
  everywhere Darwin, 1859

11
Charles Darwin and Natural Selection

• "How have all those exquisite adaptations of one
  part of the organisation to another part, and to
  the conditions of life, and of one distinct
  organic being to another being, been perfected?"
  Darwin, 1859

12
Charles Darwin and Natural Selection

• Ernst Mayr (1904-2004)
• Eminent naturalist
• Architect of the new synthesis
• Analyzed Darwins argument in On the Origin of
  Species
• A Mayr quote Being a biologist is such great
  fun!

13
Natural Selection

• Fact 1 Many more organisms are produced through
  reproduction than can survive (geometric
  increase, biotic potential)
• The principle of Malthus

14
Natural Selection

• Fact 1 Many more organisms are produced through
  reproduction than can survive (geometric
  increase, biotic potential)
• Cockroaches, rabbits, cattails
• Elephants
• People?

15
Natural Selection

• Fact 1 Many more organisms are produced through
  reproduction than can survive
• Fact 2 Population sizes of most species are
  stable on a seasonal and annual basis (in spite
  of biotic potential, population sizes do not
  increase)

16
Natural Selection

• Fact 1 Many more organisms are produced through
  reproduction than can survive
• Fact 2 Population sizes of most species are
  stable on a seasonal and annual basis
• Fact 3 Natural checks on increase

17
Natural Selection

• Fact 1 Many more organisms are produced through
  reproduction than can survive
• Fact 2 Population sizes of most species are
  stable on a seasonal and annual basis
• Fact 3 Natural checks on increase limitation
  of resources, predation, abiotic conditions

18
Natural Selection

• Fact 1 Many more organisms are produced through
  reproduction than can survive
• Fact 2 Population sizes of most species are
  stable on a seasonal and annual basis
• Fact 3 Natural checks on increase
• Inference 1 A struggle for existence

19
Natural Selection

• Two canine animals in a time of dearth, may be
  truly said to struggle with each other which
  shall get food and live. But a plant on the edge
  of the desert is said to struggle for life
  against the drought The misseltoe is dependent
  on apple and other trees, but can only in a
  far-fetched sense be said to struggle with these
  trees... Darwin, 1859

20
Natural Selection

• I use the term Struggle for Existence in a
  large and metaphorical sense, including
  dependence of one being on another, and
  includingnot only the life of the individual,
  but success in leaving progeny. Darwin, 1859

21
Natural Selection

• Fact 4 Variation in characteristics among
  individuals within populations of organic beings

22
Natural Selection
The granite grasshopper, Trimerotropis saxatilis
23
Natural Selection

• Fact 4 Variation
• Fact 5 Heritability - characteristics are passed
  from parents to offspring

24
Natural Selection

• Fact 4 Variation
• Fact 5 Heritability

25
Natural Selection

• Fact 4 Variation
• Fact 5 Heritability

26
Natural Selection
Francis Crick and James Watson elucidate the
structure of DNA - 1953
27
Natural Selection

• Fact 4 Variation
• Fact 5 Heritability
• Inference 2 Differential Reproductive Success -
  because of their characteristics, some
  individuals are more likely to survive and
  produce offspring than others
• Can we doubt... that individuals having any
  advantage, however slight, over others, would
  have the best chance of surviving and procreating
  their kind? Darwin, 1859

28
Natural Selection
Stenaspis verticalis
Plectrodera scalator
29
Natural Selection

• Fact 4 Variation
• Fact 5 Heritability
• Inference 2 Differential Reproductive Success
• Inference 3 Successful characteristics (those
  that promote individual survival and reproductive
  success) become more prevalent in the population
  (the characteristics of the population are
  modified through descent)

30
Natural Selection

• Fact 4 Variation
• Fact 5 Heritability
• Inference 2 Differential Reproductive Success
• Inference 3 Successful characteristics become
  more prevalent in the population
• Darwin's conclusion Over time, various changes
  accumulate in populations, leading to well
  adapted or designed organisms

31
Natural Selection

• Individuals differ in various phenotypic
  characteristics
• Phenotypic characteristics of individuals can be
  passed to their offspring
• Some individuals produce more offspring than
  others (because of their characteristics)
• Phenotypic characteristics that confer greater
  reproductive success become more prevalent in the
  population
• Changes accumulate in the population over time
• Accumulated changes in characteristics lead to
  better designed or adapted organisms

32
Natural SelectionThe Darwinian Mantra

• Variation
• Heritability
• Differential Reproductive success
• Spread of traits through the population
• Accumulation of change over time
• Changes in characteristics lead to better
  designed or adapted organisms

33
Natural SelectionThe Darwinian Mantra

• Heritable variation combined with differential
  reproductive success leads to the spread of
  traits through populations, which leads to
  adaptation.

34
Natural Selection

• Survival of the fittest?

35
Natural Selection

• Survival of the fittest?

36
Natural Selection

• Survival of the fittest?

37
Types of evolutionary change

• Anagenesis
• AKA Microevolution
• adaptive change within species
• descent with modification

• Cladogenesis
• AKA Macroevolution
• derivation of new species from previously
  existing ones
• transmutation of species

38
(No Transcript)
39
Natural Selection in Actionindustrial melanism
Biston betularia, the Peppered moth Typical form
Biston betularia, the Peppered moth Melanic form
40
Natural Selection in ActionBiston betularia
A mark-recapture experiment marked melanic and
typical moths were released onto polluted and
clean tree trunks, then recaptured later. The
data ( recaptured) polluted trees clean
trees melanics 34.1 6.3 typicals 16.0 12.
5
41
Natural Selection in ActionBiston betularia
Direct observations of predation melanic and
typical moths were placed onto polluted and clean
tree trunks, then observed from a blind. The
data ( attacked by birds) polluted
trees clean trees melanics 26 86 typicals 7
4 14
42
Natural Selection in ActionBiston betularia

• Criticisms of the industrial melanismstory
• Melanism is environmentally induced
• It can be, but
• Moths dont actually rest by day on tree trunks
• They do, but not exclusively
• Kettlewell glued his moths to the tree trunks
• What else was he to do?

43
Natural Selection in ActionBiston betularia

• Criticisms of the industrial melanismstory
• Changes in frequency of melanics and typicals
  doesnt match changes in lichen cover of tree
  trunks
• In Great Britain
• In the US
• The bottom line on Industrial Melanism

44
Natural Selection in ActionDarwins finches
From Sato, A. et al, 1999. Phylogeny of Darwin's
finchesPNAS 96 5101-5106
45
Natural Selection in ActionDarwins finches
From Grant, P. 1991. Natural selection and
Darwin's Finches. Scientific American
46
Natural Selection in Action
47
Natural Selection in Action
48
Natural Selection in Action
49
Natural Selection in Action
50
Natural Selection in Action
51
Natural Selection in Action
52
Natural Selection in Action -human birth weight
53
Natural Selection in Action
54
Natural Selection in Action
55
Natural Selection in Action
disruptive selection
56
Natural Selection in Action - disruptive
selection
57
Natural Selection in Action - disruptive
selection
58
Natural Selection in Action - disruptive
selection