Chapter 11 Evolution
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Transcript Chapter 11 Evolution
Evidence of Evolution
Chapter 11
11.1 Impacts/Issues
Reflections of a Distant Past
Events of the ancient past can be explained by
the same physical, chemical, and biological
processes that operate in today’s world
From Evidence to Inference
Scientists infer from evidence that an asteroid
impact near the Yucatán 65 million years ago
caused the mass extinction of dinosaurs
Mass extinction
• Simultaneous loss of many lineages from Earth
From Evidence to Inference
Barringer crater, Arizona
Pioneers of Biogeography
Late 1800s: Charles Darwin, Alfred Wallace and
other naturalists observed patterns in where
species live, how they might be related, and how
natural forces might shape life
Biogeography
• Study of patterns in the geographic distribution of
species and communities
Biogeography
Wallace and Darwin thought similarities in birds
on different continents might indicate a common
ancestor
Biogeography
Some plants that lived in similar climates on
different continents had similar features, but
were not closely related
Comparative Morphology
Naturalists studying body plans were confused
by vestigial body parts with no apparent function
Comparative morphology
• Scientific study of body plans and structures
among groups of organisms
Vestigial Body Parts
Geology
Identical rock layers in different parts of the
world, sequences of similar fossils, and fossils of
giant animals with no living representatives also
puzzled early naturalists
Confusing Discoveries
Taken as a whole, findings from biogeography,
comparative morphology, and geology did not fit
with prevailing beliefs of the 19th century
Increasingly extensive observations of nature
led to new ways of thinking about the natural
world
Comparative pelvic anatomy
11.3 A Flurry of New Theories
Nineteenth-century naturalists tried to explain
the accumulating evidence of evolution
Georges Cuvier proposed that catastrophic
geologic forces unlike those of the present day
shaped Earth’s surface (catastrophism)
Jean-Baptiste Lamarck proposed that changes
in an animal over its lifetime were inherited
Evolution
Naturalists suspected that environmental factors
affected affect a species’ traits over time,
causing changes in a line of descent
Evolution
• Change in a line of descent (in a line from an
ancestor)
Voyage of the Beagle
1831: Charles Darwin set out as a naturalist on a
five-year voyage aboard the Beagle
He found many unusual fossils and observed
animals living in many different environments
Darwin and the Voyage of the Beagle
Lyell’s Theory of Uniformity
Darwin was influenced by Charles Lyell’s
Principles of Geology, which set forth the theory
of uniformity – in contrast to catastrophism
Theory of uniformity
• Idea that gradual repetitive processes occurring
over long time spans shaped Earth’s surface
Shared Traits
Darwin collected fossils of extinct glyptodons,
which shared traits with modern armadillos
Limited Resources
Thomas Malthus observed that:
• A population tends to grow until it begins to
exhaust environmental resources—food, shelter
from predators, etc
• When resources become scarce, individuals must
compete for them
Darwin applied these ideas to the species he
had observed on his voyage
Fitness
Darwin realized that in any population, some
individuals have traits that make them better
suited to the environment than others, and
therefore more likely to survive and reproduce
Fitness
• The degree of adaptation to an environment, as
measured by an individual’s relative genetic
contribution to future generations
Adaptation
Adaptive traits that impart greater fitness to an
individual become more common in a population
over generations, compared with less
competitive forms
Adaptation (adaptive trait)
• A heritable trait that enhances an individual’s
fitness
Natural Selection
Darwin concluded that the process of natural
selection, through variations in fitness and
adaptation, is a driving force of evolution
Natural selection
• Differential survival and reproduction of
individuals of a population that vary in the details
of shared, heritable traits
Great Minds Think Alike
Alfred Wallace, the “father of biogeography”,
proposed the theory of natural selection in 1858,
at the same time as Darwin
Darwin published On the Origin of Species the
following year, in which he described descent
with modification, or evolution
Alfred Wallace
The codiscoverer of natural selection
Principles of Natural
Selection
The Galapagos Islands
11.4 About Fossils
Fossils
• Physical evidence of organisms from the past
• Hard fossils include mineralized bones, teeth,
shells, spores and other hard body parts
• Trace fossils include footprints, nests, trails, feces
and other evidence of activities
A A 30-million-year-old fossil of Elomeryx. This small terrestrial
mammal was a member of the same artiodactyl group that gave
rise to hippopotamuses, pigs, deer, sheep, cows, and whales.
Fig. 11-7a, p. 202
B Rodhocetus, an
ancient whale, lived
about 47 million years
ago. Its distinctive
ankle bones point to
a close evolutionary
connection to
artiodactyls. Inset:
compare a Rodhocetus
ankle bone (left) with
that of a modern
artiodactyl, a
pronghorn antelope
(right).
Fig. 11-7b, p. 202
C Dorudonatrox, an ancient whale that lived about 37 million years
ago. Its artiodactyl-like ankle bones (left) were much too small to
have supported the weight of its huge body on land, so this mammal
had to be fully aquatic.
Fig. 11-7c, p. 202
11.5 Putting Time Into Perspective
Transitions in the fossil record, found in
characteristic layers of sedimentary rock,
became boundaries for great intervals of the
geologic time scale
Geologic time scale
• Chronology of Earth history
• Correlates with evolutionary events
Drifting Continents, Changing Seas
Theory of continental drift
• Earth’s continents were once part of a single
supercontinent that split up and drifted apart
• Explains how the same types of fossils can occur
on both sides of an ocean
Pangea
• Supercontinent that formed about 237 million
years ago and broke up about 152 million year ago
Plate Tectonics:
A Mechanism of Continental Drift
Theory of plate tectonics
• Earth’s outer layer of rock is cracked into plates
• Slow movement rafts continents to new positions
over geologic time
• Where plates spread apart, molten rock wells up
from deep inside the Earth and solidifies
• Where plates collide, one slides under the other
and is destroyed
Plate Tectonics
Gondwana
Certain fossils of ferns and reptiles that predate
Pangea are found in similar rock layers in Africa,
India, South America, and Australia – evidence
of an even earlier supercontinent
Gondwana
• Supercontinent that formed more than 500 million
years ago
Impacts on Evolution
Evidence suggests that supercontinents have
formed and broken up at least five times
The resulting changes in the Earth’s surface,
atmosphere, waters and climates have had
profound impacts on evolution
11.6 Similarities in
Body Form and Function
Similarities in structure of body parts are often
evidence of a common ancestor
Homologous structures
• Similar body parts that reflect shared ancestry
• May be used for different purposes in different
groups, but the same genes direct their
development
Morphological Divergence
A body part that appears very different in
appearance may be quite similar in underlying
aspects of form – evidence of shared ancestry
Morphological divergence
• Evolutionary pattern in which a body part of an
ancestor changes in its descendants
(homologous structures)
Morphological
Divergence
Among Vertebrate
Forelimbs
pterosaur
chicken
penguin
stem reptile
porpoise
bat
human
elephant
Fig. 11-12, p. 208
Morphological Convergence
Some body parts look alike in different lineages,
but did not evolve in a common ancestor
Analogous structures
• Similar structures that evolved separately in
different lineages
Morphological convergence
• Evolutionary pattern in which similar body parts
evolve separately in different lineage
Morphological Convergence
Insects
Bats
Humans
Crocodiles
wings
Birds
wings
wings
limbs with
5 digits
Fig. 11-13d, p. 209
Comparative Embryology
Embryos of related species tend to develop in
similar ways
Similarities in patterns of embryonic
development are the result of master genes
(homeotic genes) that have been conserved
over evolutionary time
Comparative Embryology
Fig. 11-14a, p. 210
Fig. 11-14b, p. 210
Fig. 11-14c, p. 210
Fig. 11-14d, p. 210
Fig. 11-14e, p. 210
11.7 Biochemical Similarities
Each lineage has unique characters that are a
mixture of ancestral and novel traits, including
biochemical features such as the nucleotide
sequence of DNA
We can discover and clarify evolutionary
relationships through comparisons of nucleic
acid and protein sequences