Transcript Evidence of Evolution

Natural Selection
Questions from biogeography
 Biogeography is the
study of patterns in the
geographic distribution
of individual species
and entire
communities.
Questions from biogeography
Rhea
 Some patterns were intriguing
to early scientists.
Emu
 Many plants and animals are found
only on islands in the middle of the
ocean and other remote places.
 Other species are strikingly similar
and live far apart.
Ostrich
Questions from comparative
morphology
 The similarities and differences
among species raised questions
that gave rise to comparative
morphology: the study of body
plans and structures among
groups of organisms.
Questions from comparative
morphology
 Why do some
organisms have
useless body
parts, called
vestigial
structures?
Questions about fossils
 About the same time, geologists
were mapping layers of rock
exposed by erosion or quarrying.
 They added to the confusion when
they found fossils in the same kinds of
layers in different parts of the world.
New Theories
 19th century naturalists found themselves trying to reconcile
the evidence of change with a traditional conceptual
framework that simply did not allow for it.
George Cuvier
 Cuvier came up with the theory of
Catastrophism.
 It states that a single time of creation had
populated the world, that monstrous
earthquakes, floods, and other major
catastrophes did happen, and many living
things died.
 Each time, survivors repopulated the
world.
 There were no new species, naturalists
simply had not yet found all the fossils that
would date to the time of creation.
Georges Cuvier established
extinction events as a fact and
established the fields of
comparative anatomy and
physiology.
Problems with Cuvier
 Charles Lyell and other geologists
were arguing, erosion and other
gradual, natural processes of
change had more impact on Earth
history than rare catastrophes.
 The idea that gradual,
repetitive change had
shaped Earth became
known as the theory of
uniformity.
Charles Lyell was a well-known and
respected geologist of his time and
became a close and influential friend to
Charles Darwin.
Lyell’s Idea
 The theory of Uniformity
bothered scholars who
firmly believed that the
Earth could be no more
than 6,000 years old.
 Lyell’s calculations showed
that it must have taken
millions of years to sculpt the
present landscape.
Jean Baptiste Lamarck
 Jean Baptiste Lamarck thought
that offspring inherit traits that
a parent acquired in its
lifetime.
 By his hypothesis, environmental
pressure and internal needs
promote permanent changes in
an individual’s body form and
functions, which offspring then
inherit.
Problems with Lamarck
Although
this body
builder has
built his
muscles
during his
lifetime…
 As Lamarck correctly
inferred, the
environment is a
factor in changes in
the lines of descent.
 However, his
hypothesis has not
been supported by
environmental tests.
His children will
NOT look like
this.
Voyage of the Beagle
 In 1831, 22-yr-old
Charles Darwin joined
the crew of the Beagle,
which was about to
leave on a five-year
voyage around the
world.
Charles Darwin had 10 children.
Seven lived to adulthood, the last
died in 1943 at the age of 93!
Pictured here is William Erasmus
Darwin who died at the age of 75.
Voyage of the Beagle
 The Beagle sailed first to South America to finish mapping the coastline.
 During the Atlantic crossing, Darwin collected and studies marine life.
 He read Principles of Geology by Charles Lyell.
 He noticed diverse species in environments ranging from sandy
shores of remote islands to high mountains.
Darwin, Wallace, and Natural Selection
 Darwin’s observations of thousands of species in different
parts of the world helped him see how species might evolve.
We still have the fossils and other specimens that Darwin
collected during his voyage, including these finches!
Old Bones and Armadillos
 Darwin brought
thousands of
specimens with him
to England.
 Among the specimens
were fossils of
glyptodonts from
Argentina.
Darwin found many fossils, among which were glyptodonts. He
needed the assistance of many people to assemble and
correctly identify the fossils and specimens that he collected.
Old Bones and Armadillos
 Of all places on Earth,
armadillos live only in the
places where glyptodonts
once lived.
The Glyptodont
was a large
herbivore the size
of a car who lived
about 23-5 million
years ago.
 What if some of traits of their
common ancestor had
changed in the line of descent
that led to armadillos?
 Descent with
modification
The modern
armadillo shares
much in common
with the
glyptodont, but is
only about 30
inches long.
Key Insight—Variation in Traits
 Thomas Malthus
 He said that humans run out
of food, living space, and
other resources because they
reproduce too much.
 Individuals compete with one
another for dwindling
resources.
Thomas Malthus wrote against
popular opinion with regard to
society. Most thought we would
improve to a utopia-like state. He
had other ideas!
Key Insight—Variation in Traits
 Darwin had read Thomas Malthus
and deduced that ANY population
has a capacity to produce more
individuals than the environment can
support.
 Individuals of those species were
not alike in their details. They
varied in size, color, and other
traits.
 He thought that perhaps
variations in traits influence an
individual’s ability to secure
resources and to survive and
reproduce in the environment.
Sea Stars are voracious predators but many of their
eggs get eaten before they even hatch. Sea stars
themselves can fall prey to king crabs, sea otters, and
gulls.
Key Insight—Variation in Traits
 The Galapagos Islands are
separated from South America
by 900 kilometers of open
ocean.
 Nearly all the finch species of
the Galapagos live nowhere
else in the world, yet they
share traits with mainland
species.
There are 14 main islands and 3 minor islands of the
Galapagos. Some islands are desert-like, some are
lush and tropical, and some are both!
Key Insight—Variation in Traits
 A strong-billed finch is
better at cracking open
hard seeds.
 A drought that lasts for
several years will make
soft seeds harder to find.
Ecologists Peter and Rosemary Grant observed an
example of natural selection acting on existing traits
within a population of medium ground finches in one of
the Galapagos Islands.
1977—A drought reduced the amount of small, soft
seeds that finches preferred.
There were plenty of large, tough shelled seeds.
Because the large-beaked finches in the
population were able to crack the large, tough
seeds, they did not starve.
The next year, the Grants noted a big
increase in large-beaked hatchlings.
Most of the finches with small beaks had
died.
Natural Selection Defined
1. Traits vary from individual to individual of a species.
2. Some traits prove better at helping individuals
compete for resources, survive, and reproduce
3. Traits are inherited.
4. In time, these traits become more frequent in the
population.
o These traits can lead to an increase in fitness—an
individuals ability to reproduce and pass on traits.
Natural Selection Defined
.
Darwin’s Hesitation
 Darwin wanted his theories to be as
solid as possible. He wrote his theory
out, but didn’t publish for 10 years,
afraid of the backlash.
 Alfred Wallace
 He noticed the same patterns as Darwin.
 In 1858, both Wallace and Darwin’s
theories were presented jointly at a
scientific meeting.
 Darwin published On the Origin of
Species the following year.
Alfred Russel Wallace identified
the Wallace Line that divides the
Indonesian archipelago into two
distinct parts, one in which
animals closely related to those
of Australia are common, and
one in which the species are
largely of Asian origin
Evidence For Natural Selection
Fossils—Evidence of Ancient Life
 We have fossils for more than
250,000 known species.
 Diggers were discovering
similar rock layers and similar
sequences of fossils in distant
places, such as the cliffs on
both sides of the English
channel.
 a fossil record.
Ichthyosaurs appeared about 250 mya and
disappeared about 90 mya and grew to about 6.6-13
feet long! They resemble modern day dolphins.
Radiometric Dating
 At one time, people could assign
only relative ages to fossils.
 For instance a fossil embedded
in a layer of rock was said to be
younger than a fossil below it.
 Things changed with radiometric
dating.
 Radiometric dating has an
error factor of less than
10%.
Placing fossils in geologic time
 Researchers correlate
the geologic time scale
with
macroevolution, or
major patterns, trends,
and rates of change
among lines of descent
(lineages).
A big connection
 As geologists were mapping
vertical stacks of sedimentary
rock, they noticed some
patterns.
 The Atlantic coasts of
South America and Africa
fit like jigsaw pieces.
 These observations support
the plate tectonic theory.
Divergences from a shared ancestor
 Comparative
morphology is the
study of body forms
and structures of
major groups of
organisms.
Morphological divergence
 When populations of species stop reproducing with each
other, their traits may begin to diverge from one another.
 This is called morphological divergence.
o Body parts with similar origins but used for different
functions are known as homologous structures.
Morphological convergence
 Some body parts of different species
have similar form and function, but
evolved independently in separate
lineages.
 This is called morphological
convergence.
o Body parts without similar
origins but used for similar
purposes are also known as
analogous structures.
Similarities in patterns of development
 Embryology, the study of
embryologic
development, shows that
the embryos of some
vertebrate lineages are
alike in the early stages of
development.
What Am I?
A SNAKE!
What Am I?
A GUPPY!
What Am I?
A CHICKEN!
What Am I?
A TURTLE!
What Am I?
A MOUSE!
What Am I?
A CAT!
What Am I?
A DOG!
What Am I?
A PIG!
What Am I?
A DOLPHIN!
What Am I?
A HUMAN!