Transcript On Origin of Species by Means of Natural Selection

Chapter 4
Evolution: History and
Evidence
Evolution: History and
Evidence
• Organic Evolution
– Darwin
• “Descent with modification”
– Populations change over time.
Pre-Darwinian Theories
of Change
• Greek philosophers
– Empedocles (495-435 B.C.)
– Aristotle (384-322 B.C.)
• Buffon (1707-1788)
• Erasmus Darwin(1731-1802)
• Lamarck (1744-1829)
– Change results from “need”
Voyage of HMS Beagle
• Charles Darwin (1809-1882)
– Boarding school
– Edinburgh medical school
– Christ’s College Cambridge
– Nominated by Henslow to serve as
naturalist on HMS Beagle (1831)
– On Origin of Species by Means of
Natural Selection (1859)
Figure 4.1 Voyage of the HMS Beagle.
Early Development of
Darwin’s Ideas of Evolution
• Geology
– Hutton and uniformitarianism
• Geological change occurs over hundreds
of millions of years.
– Earth is much older than 6,000 years.
– Could not living forms change as
well?
Early Development of
Darwin’s Ideas of Evolution
• Fossil evidence
– South American
fossils
Figure 4.2a The giant
sloth.
Early Development of
Darwin’s Ideas of Evolution
• Galapagos
Islands
– Tortoises
– Finches
• Adaptive radiation
– The formation of
new forms from
an ancestral
species
Figure 4.3a Galapagos tortoise
(Geochelone elephantopus).
Figure 4.4 Adaptive radiation of Galapagos finches.
The Theory of Evolution by
Natural Selection
• Other
observations
– Artificial selection
– Thomas Malthus
(1766-1834)
Figure 4.5 Artificial
selection in Canis lupis. The
147 breeds of dogs
recognized by the AKC
originated from artificial
selection of wolf ancestors.
The grey wolf (a), Shetland
Sheep Dog (b), and Irish
Wolfhound (c).
(b)
(a)
(c)
The Theory of Evolution by
Natural Selection
1. High reproductive potential
2. Inherited variation exists.
3. Constant struggle for limited
resources, many individuals die.
4. Adaptive traits become more
common in subsequent
generations.
Adaptation
• Occurs when a
HERITABLE
CHANGE IN
PHENOTYPE
increases an
animal’s chances
of SUCCESSFUL
REPRODUCTION
– Examples?
• Arise as a result of
chance mutations
• Perpetuated by
natural selection
Figure 4.6 Adaptations of the
Arctic Hare (Lepus articus).
Alfred Russel Wallace
(1823-1913)
• Theory of evolution similar to
Darwin’s
• Published ideas jointly with Darwin
• Impetus for Darwin’s publication of
On the Origin of Species by Means
of Natural Selection
• Darwin given credit
– Years of work
– Massive accumulations of evidence
Microevolution,
Macroevolution, and
Evidence of
Macroevolutionary Change
• Microevolution
– Change in the frequency of alleles in
a population over time
• Macroevolution
– Large-scale changes that result in
the extinction and formation of new
species
Biogeography
• Study of the geographic
distribution of plants and animals
• Life-forms in different parts of
• the world have distinctive
evolutionary histories.
• Biogeographers attempt to
explain distribution patterns.
Figure 4.7 Biogeography as evidence of evolutionary
change.
Figure 4.8 Biogeographic regions of the world.
Paleontology
• Fossils
– Evidence of plants and animals that
existed in the past and have become
incorporated into the earth’s crust
• Direct evidence of sequences of
appearance and disappearance of
organisms
Paleontology
Figure 4.9 Fossils like this trilobite
are direct evidence of evolutionary
change.
Figure 4.10 The fossil
record gives evidence of
the horse lineage.
Analogy and Homology
• Convergent evolution
– Evolution of superficially similar
structures in unrelated organisms
– Similar structures are analogous.
• Homology
– Resemblance that occurs because of
common ancestry
Homology—Comparative
Anatomy
• Study of the
structure of living
and fossilized
animals and
homologies that
indicate close
relationships
Figure 4.11 Vertebrate
forelimbs evolved from an
ancestral pattern.
Figure 4.12 Evolution of the vertebrate ear ossicles.
Figure 4.13 Vestigial structures have no apparent
function in an animal, but evolved from functioning
structures in ancestors.
Homology—Developmental
Patterns
• Developmental
stages of related
animals often retain
common features.
• Changes in genes
controlling
development are
usually harmful and
eliminated by
natural selection.
Figure 4.14 Early developmental
stages of vertebrates are similar.
Homology—Molecular
Biology
• Study of nuclear DNA, mitochondrial
DNA, ribosomal RNA, and proteins
• Molecules provide direct evidence of
change in genes.
• Genetic similarity (degree of
relatedness) is reflected in variation
in amino acid sequences in proteins
and base sequences in DNA.
Interpreting the Evidence:
Phylogeny and Common
Descent
• Phylogeny
– Evolutionary relationships among
species
Phylogenetic Trees
• Show lines of
descent
• Branches
– Evolutionary
connections
• Nodes
– Branch points
– Genes,
populations, or
species where a
change occurs
Modern Synthesis
• Principles of modern genetics
combined with Darwinian
evolutionary theory
• Chapter 5