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Evolution
• Central theme of Biology
• Look at any organism
• Differences from other other organisms
• Organism features show some relationship to where organism
lives and what it does in its environment
Clown, Fool, or Simply Well Adapted?
• All organisms have evolutionary adaptations
• Inherited characteristics that enhance their ability to survive
and reproduce
• Universal characteristic of living things.
• The blue-footed booby of the
Galápagos Islands has features
that help it succeed in its
environment
• Large, webbed feet help
propel the bird through
water at high speeds
• A streamlined shape, large tail, and nostrils that close are
useful for diving
– Specialized salt-secreting glands manage salt
intake while at sea
EVIDENCE OF EVOLUTION
13.1 A sea voyage helped Darwin frame
his theory of evolution
• Anaximander suggested all life from water, and simpler forms came
before more complex.
• Aristotle, and tater advanced by the Judeo-Christian culture, believed
that species are fixed or were created about 6000 years ago, and did not
evolve
• Buffon thought the earth was older, and thought different species from
common ancestors (later changed mind)
• Fossils suggested that life forms change
• This idea was embraced by Lamarck in the early 1800s
• Mechanism for change was inheritance of acquired characteristics.
• ???, You need something you get it
• While on the voyage of the HMS Beagle in the 1830s,
Charles Darwin observed
– similarities between living and fossil organisms
– the diversity of life on the Galápagos Islands,
such as blue-footed boobies and giant tortoises
Figure 13.1A
• The voyage of the Beagle
Great
Britain
Europe
North
America
Pacific
Ocean
Atlantic
Ocean
Africa
Galápagos
Islands
Equator
South
America
Australia
Cape of
Good Hope
Tasmania
Cape Horn
Tierra del Fuego
New
Zealand
Figure 13.1B
• Darwin became convinced that the Earth was old and continually
changing (He was influenced by Lyell).
• Compared fossils on the different Galapagos Islands to each each.
• Compared fossils on the Galapagos to fossils in S. America.
• He concluded that living things also change, or evolve
over generations
• Wallace conceived same theory based on observations in
Indonesia. Both presented work to scientific community
• Darwin also stated that living species descended from
earlier life-forms: descent with modification,
encapsulates idea of evolution
The history of life is like a tree
You have a base that grows
and eventually branches
out. Species on one
branch are closer related
than species on another
branch
13.2 The study of fossils provides strong
evidence for evolution
• Fossils and the fossil record strongly
support the theory of evolution
• Hominid skull
– Petrified trees
Figure 13.2A, B
• Ammonite casts
– Fossilized organic
matter in a leaf
Figure 13.2C, D
• Scorpion in amber
– “Ice Man”
– Preserved for 5000
yrs
Figure 13.2E, F
• The fossil record shows that organisms
have appeared in a historical sequence.
• These are layers of sedimentary rock,
formed from accumulation of waterborne
sediments
• Younger strata on surface with more recent
organisms
• Oldest fossils, prokaryotes, date back to 3.5
billion years ago in bottom layers of strata.
• Ongoing sequence of intermediate steps
going from simple to more complex
Figure 13.2G, H
• Many fossils link early
extinct species with
species living today
• These fossilized hind
leg bones link living
whales with their landdwelling ancestors
13.3 A mass of evidence validates the
evolutionary view of life
• Other evidence for evolution comes
from
• Biogeography
• Related life forms around world
• Island species look like closest
mainlaind, not always closest island
• Comparative
anatomy (all basic limb structure)
• Comparative
embryology (all vertebrates and
chordates had gill pouches in throat
region
Human
Cat
Whale
Bat
Figure 13.3A
• Molecular biology
• Universality of genetic code
• Similar homeotic genes in different species
Human
Rhesus monkey
Last common
ancestor lived
26 million years
ago (MYA),
based on
fossil evidence
Mouse
Chicken
Frog
Lamprey
80 MYA
275 MYA
330 MYA
450 MYA
Figure 13.3B
DARWIN’S THEORY AND THE MODERN
SYNTHESIS
13.4 Darwin proposed natural selection
as the mechanism of evolution
• Darwin observed that
• organisms produce more offspring than the environment can
support
• organisms vary in many characteristics, expression of traits
• these variations can be inherited, genetic
• Darwin concluded that individuals best suited for a
particular environment are more likely to survive and
reproduce than those less well adapted
• Darwin saw natural selection as the basic
mechanism of evolution
– As a result, the proportion of individuals with
favorable characteristics increases
– Populations gradually change in response to the
environment
• Darwin also saw that when humans
choose organisms with specific
characteristics as breeding stock,
they are performing the role of the
environment
– This is called artificial
selection
– Example of artificial
selection in plants: five
vegetables derived from
wild mustard
Figure 13.4A
• Example of artificial selection in animals: dog breeding
German shepherd
Yorkshire terrier
English springer
spaniel
Mini-dachshund
Golden retriever
Hundreds to
thousands of years
of breeding
(artificial selection)
Ancestral dog
Figure 13.4B
• These five canine species evolved from a common
ancestor through natural selection
African wild
dog
Coyote
Fox
Wolf
Jackal
Thousands to
millions of years
of natural selection
Ancestral canine
Figure 13.4C
Two important point’s from Darwin’s
theory of Natural Selection
• Ancestral species gave rise to diverse life forms by
transfer of heritable traits to offspring that best
promote reproduction = “descent with modification
• Over vast amounts of time, gradual accumulation of
changes in the characteristics among the individuals in a
population changes
13.5 Connection: Scientists can observe
natural selection in action
• Evolutionary adaptations have been observed in
populations of birds, insects, and many other organisms
• Example: camouflage adaptations of mantids that live in
different environments
Figure 13.5A
• The evolution of insecticide resistance is an example of
natural selection in action
Apply same theory to
antibiotics – don’t
finish, build up of
bacterial resistance
Insecticide
application
Chromosome with gene
conferring resistance
to insecticide
Additional
applications of the
same insecticide will
be less effective, and
the frequency of
resistant insects in
the population
will grow
Survivor
Figure 13.5B
• Natural selection is regional and timely. Populations
tend to evolve in response to environmental conditions
during one time period
• Change can occur in very short periods of time, think of
life span or life cycle of organism
• Or over long periods of time
13.6 Populations are the units of
evolution
• A species is a group of populations whose individuals
can interbreed and produce fertile offspring
• Human populations tend
to concentrate locally, as
this satellite photograph
of North America shows
• The modern synthesis
connects Darwin’s theory
of natural selection with
population genetics
Figure 13.6
• Evolution is measured as a change in frequency of a
given characteristic within a population over succession
of generations.
• i.e. Height, average goes up, humans are evolving to be taller
as a species
• Opportunities for breeding among a population varies
depending on species and isolation of certain populations.
City vs. Forest
13.7 Microevolution is change in a
population’s gene pool over time
• A gene pool is the total collection of genes in a
population at any one time
• Microevolution is a change in the relative frequencies of
alleles in a gene pool
• Frequencies of alleles governing characteristics change
• Insect resistance. Insects with resistance alleles w/ higher
frequency then insects with minimal resistance alleles
depending on if a field sprayed with pesticide or not