Introduction to
Darwinian Evolution
Chapter 18
Learning Objective 1
•
What is evolution?
Evolution
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Accumulation of inherited changes within a
population over time
•
Unifying concept of biology
•
links all fields of life sciences into a unified
body of knowledge
Learning Objective 2
•
Discuss the historical development of the
theory of evolution
Jean Baptiste de Lamarck
•
Proposed that organisms
•
•
•
change over time by natural phenomena, not
divine intervention
had vital force that changed them toward
greater complexity over time
could pass traits acquired during lifetime to
offspring
Charles Darwin
•
Theory of evolution
•
•
Based on observations during voyage of
HMS Beagle
Found similarities between organisms
•
•
on arid Galápagos Islands
on humid South American mainland
Voyage of HMS Beagle
Darwin
•
Influenced by artificial selection
•
•
Applied Thomas Malthus’s ideas
•
•
variety of domesticated plants and animals
on human populations to natural populations
Influenced by geologists (Charles Lyell)
•
idea that Earth was extremely old
Genetic Variation
•
Artificial selection
•
Natural Variation
KEY CONCEPTS
•
Ideas about evolution originated long
before Darwin’s time
Learning Objective 3
•
What are the four premises of evolution by
natural selection as proposed by Charles
Darwin?
4 Premises of Evolution
by Natural Selection
1. Genetic variation
•
exists among individuals in population
2. Reproductive ability of each species
•
causes populations to geometrically
increase over time
4 Premises of Evolution
3. Organisms compete with one another
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for resources: food, living space, water, light
4. Offspring with most favorable characteristics
•
•
most likely to survive and reproduce
pass genetic characteristics to next generation
Natural Selection
•
Results in adaptations
•
•
•
evolutionary modifications
improve chances of survival and reproductive
success in a particular environment
Over time
•
accumulated changes in geographically
separated populations produce new species
KEY CONCEPTS
•
Darwin’s voyage on the Beagle provided
the basis for his theory of evolution by
natural selection
Galapagos Finches
Fig. 18-4a, p. 395
Fig. 18-4b, p. 395
Fig. 18-4c, p. 395
Animation: The Galapagos
Islands
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TO PLAY
KEY CONCEPTS
•
Natural selection occurs because
individuals with traits that make them
better adapted to local conditions are more
likely to survive and produce offspring than
are individuals that are not as well adapted
Learning Objective 4
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What is the difference between the
modern synthesis and Darwin’s original
theory of evolution?
Modern Synthesis
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Or synthetic theory of evolution
•
•
combines Darwin’s theory of evolution by
natural selection with modern genetics
Explains
•
•
why individuals in a population vary
how species adapt to their environment
Mutation
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Provides genetic variability
•
that natural selection acts on during evolution
KEY CONCEPTS
•
The modern synthesis combines Darwin’s
theory with genetics
Learning Objective 5
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What evidence for evolution can be
obtained from the fossil record?
Fossil Record
•
Fossils
•
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remains or traces of ancient organisms
provide direct evidence of evolution
Fossil Record
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Sedimentary rock
•
•
•
Index fossils
•
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layers occur in sequence of deposition
recent layers on top of older ones
characterize specific layer
Radioisotopes
•
in rock accurately measure rock’s age
Sedimentary Rock
Fossils
Whale
Evolution
Mesonychid
Fig. 18-8a, p. 399
Ambulocetus natans
Fig. 18-8b, p. 399
Rodhocetus
Fig. 18-8c, p. 399
Basilosaurus
Fig. 18-8d, p. 399
Balaenoptera
Fig. 18-8e, p. 399
Radioisotope Decay
Learning Objective 6
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What evidence for evolution is derived
from comparative anatomy?
Homologous Features
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Basic structural similarities
•
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Derived from same structure
•
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structures may be used in different ways
in common ancestor
Indicate organism’s evolutionary affinities
Homology in Animals
HUMAN
BAT
WHALE
CAT
Humerus
Humerus
Radius
Ulna
Carpal
5
Radius
Ulna
Metacarpal
4
Carpal
1
Radius
Ulna
1
5
Carpal
1
Metacarpal
3
2
Phalanges 4
1
Phalanges
2
5
4
5
43
2
2
3
3
Fig. 18-10, p. 401
HUMAN
BAT
WHALE
CAT
Humerus
Humerus
Radius
Ulna
Carpal
5
Radius
Ulna
Metacarpal
4
Carpal
1
Radius
Ulna
1
5
Carpal
1
Metacarpal
3
2
Phalanges 4
1
Phalanges
2
5
4
3
5
43
2
2
3
Stepped Art
Fig. 18-10, p. 401
Homology in Plants
Spine
Fig. 18-11a, p. 401
Tendril
Leaflet
Leaf petiole
Stipule
Stem
Fig. 18-11b, p. 401
Homoplastic Features
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Evolved independently
•
•
similar functions in distantly related organisms
Demonstrate convergent evolution
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organisms with separate ancestries adapt
similarly to comparable environments
Aardvark (Orycteropus afer)
Fig. 18-12a, p. 402
Giant anteater (Myrmecophaga tridactyla)
Fig. 18-12b, p. 402
Pangolin (Manis crassicaudata)
Fig. 18-12c, p. 402
Homoplasy
Shoot
(develops
from axillary
bud)
Spine
(midrib
of leaf)
Leaf scar
A spine of Japanese barberry (Berberis thunbergii) is a modified leaf.
(In this example, the spine is actually the midrib of the original leaf,
which has been shed.)
Fig. 18-13a, p. 403
Thorn (develops from
axillary bud)
Thorns of downy hawthorn (Crataegus mollis) are modified stems
that develop from auxillary buds
Fig. 18-13b, p. 403
Vestigial Structures
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Nonfunctional or degenerate remnants
•
•
of structures functional in ancestral organisms
Structures occasionally become vestigial
•
as species adapt to different modes of life
Vestigial Structures
Learning Objective 7
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What is biogeography?
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How does distribution of organisms
support evolution?
Biogeography
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Geographic distribution of organisms
•
•
affects evolution
Areas separated from the rest of the world
•
•
contain organisms evolved in isolation
unique to those areas
Continental Drift
•
At one time, continents were joined to form
a supercontinent
•
Continental drift
•
•
caused landmasses to separate
played major role in evolution
Continental Drift
Pangaea
Fig. 18-15a, p. 404
Laurasia
Gondwana
Fig. 18-15b, p. 404
Asia
N. America
Europe
Africa
S.
America
India
Australia
Antarctica
Fig. 18-15c, p. 404
N.
America
Eurasia
Africa
S.
America
Australia
Antarctica
Fig. 18-15d, p. 404
Fossil
Distribution
Cynognathus
Lystrosaurus
(a)
(b)
Africa
India
South
America
Australia
Antarctica
(c)
Mesosaurus
Glossopteris
(d)
Fig. 18-16, p. 405
Learning Objective 8
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How do developmental biology and
molecular biology provide insights into the
evolutionary process?
Evolutionary Changes
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Often result of gene mutations that affect
events in development
•
Development in different animals
•
•
controlled by same kinds of genes
indicates shared evolutionary history
Genetic Changes
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Accumulation of genetic changes
•
•
since organisms diverged
modified development patterns in more
complex vertebrate embryos
Divergence in Whales
Cetaceans
(whale, dolphin)
Hippopotamus
Ruminants
(cow, sheep,
giraffe)
Pig
Camel
Artiodactyls
Common
ancestor of
hippos and
whales
Common ancestor of
artiodactyls and
cetaceans
Fig. 18-17, p. 407
Molecular Evidence
for Evolution
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Universal genetic code
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Conserved sequences
•
•
of amino acids in proteins
of nucleotides in DNA
Molecular Clock
Learning Objective 9
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How are evolutionary hypotheses tested
experimentally?
Reznick and Endler
•
Studied effects of predation intensity
•
•
on evolution of guppy populations in
laboratory and nature
Tested underlying processes of natural
selection
Reznick Experiment
KEY CONCEPTS
•
The evidence that evolution has taken
place and is still occurring is overwhelming
Animation: Radiometric Dating
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TO PLAY
Animation: Morphological
Divergence
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TO PLAY
Animation: Radioisotope Decay
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Video: Creation vs. Evolution
CLICK
TO PLAY
•
From ABC News, Environmental Science in the Headlines, 2005 DVD.
Video: Dinosaur Discovery
CLICK
TO PLAY
•
From ABC News, Environmental Science in the Headlines, 2005 DVD.