History of Evolutionary Thought

1

• History of Evolutionary Thought
• Before Darwin
• Concept of evolution predates Darwin by gt2000
  years (not widely accepted)
• Fossils known long before Darwin and recognized
  as remains of organisms
• Aristotle (384-322 B.C.)
• Organisms could be arranged on a natural scale of
  increasing complexity (scala naturae)
• Species fixed and unchanging
• Carolus Linnaeus (1707-1778)
• Swedish physician who founded taxonomy
• Believed in natural theology (study nature to
  understand the Creator)
• Developed binomial nomenclature and modern
  classification hierarchy
• Did not intend system to reflect evolutionary
  relationships

2
Natural theology, taxonomy, binomial nomenclature
Gradualism
Natural change w/o divine guidance use disuse
(adaptation) inherit acquired traits
Paleontology, catastrophism (local) b/w strata
Uniformitarianism
Fig. 22.2
3

• History of Evolutionary Thought
• Before Darwin
• James Hutton (1726-1797)
• Gradualism
• Jean Baptiste de Lamarck (1744-1829)
• Old earth, adaptation, evolution
• Thomas Malthus (1766-1834)
• Population increase ? Competition for survival
• Georges Cuvier (1769-1832)
• Paleontology, extinction, catastrophism
• Charles Lyell (1797-1875)
• Uniformitarianism

4

• History of Evolutionary Thought
• Charles Darwin (1809-1882)
• Went to University of Edinburgh at 16 to study
  medicine
• Transferred to Cambridge University changed
  major to theology
• Became protégé of botanist
• Initial observations for theory of evolution made
  on 5-year cruise to prepare navigation charts for
  British Navy naturalist aboard HMS Beagle
• 1831-1836

5
Fig. 22.5
6

• History of Evolutionary Thought
• Charles Darwin (1809-1882)
• Crucial information for development of theory
• Similarities differences among species in
  Galapagos Islands vs. South America
• Suggested divergence from common ancestor
• Principles of Geology (1830) by Lyell
• Gradualism contradicted idea of static, young
  earth
• Artificial selection
• Selective breeding in dogs, cattle, wild mustard

7
Fig. 22.9
8

• History of Evolutionary Thought
• Charles Darwin (1809-1882)
• Crucial information for development of theory
• Similarities differences among species in
  Galapagos Islands vs. South America
• Suggested divergence from common ancestor
• Principles of Geology (1830) by Lyell
• Gradualism contradicted idea of static, young
  earth
• Artificial selection
• Selective breeding in dogs, cattle, wild mustard
• Writings of Malthus on population growth
• Suggested that not all offspring can survive when
  resources are limited

9

• History of Evolutionary Thought
• Charles Darwin (1809-1882)
• Major components of evolutionary theory
• Descent with Modification
• Recognized that groups in Linnaeus
  classification hierarchy could reflect patterns
  of descent from common ancestors
• Natural Selection
• Mechanism by which populations adapted to local
  conditions
• Developed from five major observations and three
  inferences (according to Ernst Mayr)

10

• History of Evolutionary Thought
• Charles Darwin (1809-1882)
• Observations
• Overproduction Not all offspring survive to
  reproduce
• Stability Populations tend to remain stable in
  size
• Limited Resources
• Within-Species Variation Not all individuals
  identical
• Heritability Traits passed from parent to
  offspring
• Inferences
• Competition Leads to limited survivorship
• Differential Fitness Best adapted individuals
  most likely to survive
• Gradual Change Favorable traits accumulate over
  generations

11

• Evidence for Evolutionary Theory
• Natural Selection
• Has been tested experimentally

12
Fig. 22.13
13
Fig. 22.14
14

• Evidence for Evolutionary Theory
• Natural Selection
• Has been tested experimentally
• Guppies
• Drug resistance

15

• Evidence for Evolutionary Theory
• Anatomical Homologies
• Homologous features derived from same structure
  in ancestor
• Homoplastic features arose from same functional
  need (convergent evolution)
• Some important clues to ancestry come from
  vestigial structures
• Ex Hindlimb bones in whales and some large snakes

16
Fig. 22.17
17

• Evidence for Evolutionary Theory
• Embryological Homologies
• Features in early development often conserved
  throughout a taxon
• Ex Gill pouches and tail in mammals, just like
  fishes, amphibians, reptiles, birds
• Molecular Homologies
• Divergent traits based on divergent genes and
  proteins
• Some proteins and parts of proteins diverge more
  than others (some regions conserved)

18
Fig. 22.18
19

• Evidence for Evolutionary Theory
• Biogeography
• Geographic distribution reflects ancestral
  relationships
• Ex Nearly all living marsupials restricted to
  Australia and nearby islands
• Fossil Record
• Appearance, location, time of extinct species
• Some evolutionary intermediates

20
Fig. 22.16
21

• Evidence for Evolutionary Theory
• Fossil Record
• Biases
• Not all organisms fossilized equally (jellyfish
  vs. fish)
• Fossil-bearing rocks typically form from fine
  sediments (species away from fine sediments
  preserved less frequently)
• Tropical rain forest species decompose rapidly
  before fossilizing
• Fossil record biased toward organisms with hard
  parts living in aquatic or arid terrestrial
  environments