Download 15-3 Darwin Presents His Case

Biology
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15-1 The Puzzle of Life's
Diversity
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15-1 The Puzzle of Life's Diversity
15-1 The Puzzle of Life's Diversity
Diversity
Evolution is the process by which modern organisms
have descended from ancient organisms.
A scientific theory is a well-supported testable
explanation of phenomena that have occurred in the
natural world.
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15-1 The Puzzle of Life's
Diversity
Voyage of the Beagle
Voyage of the Beagle
In 1831, Darwin set sail from England aboard the
H.M.S. Beagle for a voyage around the world.
Darwin went ashore and collected plant and animal
specimens for his collection.
He studied the specimens, read the latest scientific
books, and filled many notebooks with his
observations and thoughts.
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15-1 The Puzzle of Life's
Diversity
Voyage of the Beagle
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15-1 The Puzzle of Life's
Diversity
Voyage of the Beagle
What was Charles Darwin's contribution
to science?
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15-1 The Puzzle of Life's
Diversity
Voyage of the Beagle
During his travels, Darwin made
numerous observations and collected
evidence that led him to propose a
hypothesis about the way life changes
over time.
That hypothesis has become the theory of
evolution.
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15-1 The Puzzle of Life's
Diversity
Darwin's Observations
Darwin's Observations
Darwin observed that many plants and animals
were well suited to the environments they
inhabited.
He was impressed by the ways in which organisms
survived and produced offspring.
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Diversity
Darwin's Observations
Darwin was puzzled by where different species lived
and did not live.
Grasslands in some regions were similar to one
another but were inhabited by very different animals.
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15-1 The Puzzle of Life's
Diversity
Darwin's Observations
Living Organisms and Fossils
Darwin collected the preserved remains of ancient
organisms, called fossils.
Some of those fossils resembled organisms that
were still alive.
Others looked completely unlike any creature he
had ever seen.
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15-1 The Puzzle of Life's
Diversity
Darwin's Observations
The Galápagos Islands
Darwin observed that the Galápagos Islands were
close together but had very different climates.
The Beagle was in the Galapagos for five weeks,
from 15 September to 20 October 1835, and made a
series of charts which were still in use by mariners in
the 1940s.
Darwin landed at only four of the islands (San
Cristobal, Floreana, Santiago, and Isabela); his
wonder would have been all the greater had he
visited other islands, for the same pattern is repeated
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throughout the archipelago.
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15-1 The Puzzle of Life's
Diversity
The Journey Home
The Journey Home
What pattern did Darwin observe among
organisms of the Galápagos Islands?
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15-1 The Puzzle of Life's
Diversity
The Journey Home
Darwin observed that the characteristics
of many animals and plants varied
noticeably among the different islands of
the Galápagos.
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Diversity
The Journey Home
Darwin wondered if animals living on different islands had
once been members of the same species.
These separate species would have evolved from an
original South American ancestor species.
In 1837, a year after the return of H.M.S. Beagle, Darwin
started to formulate his thoughts on the idea of evolution.
In March, he was told by the ornithologist John Gould that
the finches found on seven islands of Galapagos differed
from one another on a specific level. At this point, Darwin
was finally sure that geological separation played a very
important part in the formation of new species: in different
environments, species changed gradually over time in
different ways to adapt to the local environment.
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Darwin's observations in the Galápagos Islands
included all of the following EXCEPT
a. characteristics of many living organisms did
not vary among the different Galápagos
Islands.
b. many plants and animals were well suited to
their environments.
c. very different animals inhabited many similar
ecosystems.
d. though close together, the islands had very
different climates.
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15-1
What did Darwin learn about the tortoises of the
Galápagos Islands?
a. Tortoises with dome-shaped shells were
found on all of the islands.
b. The tortoises resembled fossil remains that
were found on the islands.
c. The shape of the Galápagos tortoise shells
varied with their different habitats.
d. Different shaped tortoise shells occupied the
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According to Darwin's proposed theory of
evolution, species of organisms
a. change over time.
b. are not related to fossil remains.
c. do not vary from one location to another.
d. remain unchanged when the environment
changes.
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Darwin hypothesized that different-looking
mockingbirds from different islands might be
descendants of birds that
a. belonged to a single species that had
originated on the islands.
b. belonged to a single species from the South
American mainland.
c. belonged to a different species from similar
habitats in South America.
d. had been brought to the islands by earlier
visitors.
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What role did the evidence gathered by Darwin
play in developing his ideas?
a. It immediately gave him the idea that
organisms evolved.
b. It confirmed evolution—an idea he had
before he left England.
c. It confirmed evolution, which he proved on
his arrival in the Galápagos.
d. It led to considering the possibility of
evolution only after he was heading home.
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END OF SECTION
Biology
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15–2 Ideas That Shaped
Darwin's Thinking
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15–2 Ideas That Shaped
Darwin's Thinking
An Ancient, Changing Earth
An Ancient, Changing Earth
How did Hutton and Lyell describe
geological change?
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15–2 Ideas That Shaped
Darwin's Thinking
An Ancient, Changing Earth
Hutton and Lyell helped scientists
recognize that Earth is many millions of
years old, and the processes that
changed Earth in the past are the same
processes that operate in the present.
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15–2 Ideas That Shaped
Darwin's Thinking
An Ancient, Changing Earth
Hutton and Geological Change
In 1795, James Hutton published a hypothesis
about the geological forces that shaped Earth.
Most of these geological forces operate very
slowly, over millions of years.
Hutton proposed that Earth had to be much more
than a few thousand years old.
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15–2 Ideas That Shaped
Darwin's Thinking
An Ancient, Changing Earth
Lyell's Principles of Geology
Lyell stressed that scientists must explain past
events in terms of processes that they can actually
observe.
The processes that shaped the Earth millions of
years earlier continue in the present.
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15–2 Ideas That Shaped
Darwin's Thinking
An Ancient, Changing Earth
Lyell’s work explained how geological features could
be built up or torn down over long periods of time.
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15–2 Ideas That Shaped
Darwin's Thinking
An Ancient, Changing Earth
This understanding of geology influenced Darwin:
• If the Earth could change over time, life might
change as well.
• It would have taken many years for life to change
in the way Lyell suggested.
This would have been possible only if the Earth were
extremely old.
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15–2 Ideas That Shaped
Darwin's Thinking
Lamarck’s Evolution Hypotheses
According to Lamarck, how did species
evolve?
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15–2 Ideas That Shaped
Darwin's Thinking
Lamarck's Evolution Hypotheses
Lamarck's Evolution Hypotheses
Jean-Baptiste Lamarck recognized that:
• living things have changed over time.
• all species were descended from other
species.
• organisms were adapted to their environments.
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15–2 Ideas That Shaped
Darwin's Thinking
Lamarck's Evolution Hypotheses
Lamarck proposed that by selective use
or disuse of organs, organisms acquired
or lost certain traits during their lifetime.
These traits could then be passed on to
their offspring. Over time, this process
led to change in a species.
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15–2 Ideas That Shaped
Darwin's Thinking
Lamarck's Evolution Hypotheses
Tendency Toward Perfection
Lamarck proposed that all organisms have an
innate tendency toward complexity and perfection.
They are continually changing and acquiring
features that help them live more successfully in
their environments.
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15–2 Ideas That Shaped
Darwin's Thinking
Lamarck's Evolution Hypotheses
Use and Disuse
Lamarck proposed that organisms could alter the
size or shape of particular organs by using their
bodies in new ways.
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15–2 Ideas That Shaped
Darwin's Thinking
A male fiddler
crab uses its front
claw to ward off
predators and to
attract mates.
Lamarck's Evolution Hypotheses
Lamarck's Hypothesis
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15–2 Ideas That Shaped
Darwin's Thinking
Because the front
claw is used
repeatedly, it
becomes larger.
Lamarck's Evolution Hypotheses
Lamarck's Hypothesis
This characteristic
(large claw) is
passed onto its
offspring.
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15–2 Ideas That Shaped
Darwin's Thinking
Lamarck's Evolution Hypotheses
Inheritance of Acquired Traits
Lamarck thought that acquired characteristics
could be inherited.
He believed that if an animal acquired a particular
feature in its lifetime, that feature would be passed
on to its offspring.
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15–2 Ideas That Shaped
Darwin's Thinking
Lamarck's Evolution Hypotheses
Evaluating Lamarck's Hypotheses
Lamarck’s hypotheses of evolution are incorrect in
several ways.
Lamarck did not know:
• how traits are inherited.
• that an organism’s behavior has no effect on
its heritable characteristics.
However, he paved the way for the work of later
biologists.
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15–2 Ideas That Shaped
Darwin's Thinking
Population Growth
What was Malthus's theory of
population growth?
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15–2 Ideas That Shaped
Darwin's Thinking
Population Growth
Population Growth
In 1798, Thomas Malthus published a book in
which he noted that babies were being born faster
than people were dying.
The only forces he observed that worked against
this growth were war, famine, and disease.
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15–2 Ideas That Shaped
Darwin's Thinking
Population Growth
Malthus reasoned that if the human
population continued to grow
unchecked, sooner or later there would
be insufficient living space and food for
everyone.
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15–2 Ideas That Shaped
Darwin's Thinking
Population Growth
When Darwin read Malthus’s work, he realized that
this reasoning applied to plants and animals.
If all the offspring of almost any species survived for
several generations, they would overrun the world.
This information was central to Darwin’s explanation
of evolutionary change.
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15–2
Hutton and Lyell recognized that geological
processes
a. of the past differ from those of the present.
b. indicate that Earth is many millions of years
old.
c. operate quickly, often over thousands of
years.
d. always involve violent events like volcanoes,
earthquakes, and floods.
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15–2
The discovery of many fossils challenged the
idea that
a. acquired traits could be inherited.
b. Earth is many millions of years old.
c. species had never changed over time.
d. geological changes are slow.
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15–2
Which of the following scientists proposed the
hypothesis of selective use and disuse?
a. Charles Darwin
b. Jean-Baptiste Lamarck
c. Thomas Malthus
d. Charles Lyell
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15–2
The scientist that proposed that Earth is shaped
by geological forces that took place over long
periods of time is:
a. Malthus
b. Hutton
c. Darwin
d. Lamarck
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15–2
Darwin’s reading of Thomas Malthus made him
realize that
a. because of overpopulation, human beings
cannot avoid extinction.
b. all living things must evolve.
c. living things produce more offspring than can
possibly survive.
d. the basic ideas of Lamarck were wrong.
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END OF SECTION
Biology
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15-3 Darwin Presents
His Case
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15-3 Darwin Presents His Case
Publication of On the Origin of
Species
Publication of On the Origin of Species
Darwin filled notebooks with his ideas about
species diversity and the evolution process.
Darwin was stunned and disturbed by his
discoveries.
He shelved his manuscript for years and told his
wife to publish it in case he died.
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Publication of On the Origin of
Species
In 1858, Darwin received a short essay from
naturalist Alfred Wallace.
The essay summarized Darwin’s thoughts on
evolutionary change.
Later that year, Wallace’s essay was presented with
some of Darwin’s work.
In 1859, Darwin published his book, On the Origin of
Species.
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Publication of On the Origin of
Species
In his book, Darwin:
• proposed a mechanism for evolution called
natural selection.
• presented evidence that evolution has been
taking place for millions of years—and continues
in all living things.
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15-3 Darwin Presents His Case
Inherited Variation and Artificial
Selection
Inherited Variation and Artificial Selection
Members of each species vary from one another
in important ways.
In Darwin’s day, variations were thought to be
unimportant, minor defects.
Darwin argued that this variation mattered.
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15-3 Darwin Presents His Case
Inherited Variation and Artificial
Selection
Darwin noted that plant and animal breeders would
breed only the largest hogs, the fastest horses, or the
cows that produced the most milk.
Darwin termed this process artificial selection.
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15-3 Darwin Presents His Case
Inherited Variation and Artificial
Selection
How is natural variation used in artificial
selection?
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Inherited Variation and Artificial
Selection
Artificial selection is the selection by
humans for breeding of useful traits
from the natural variation among
different organisms.
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Inherited Variation and Artificial
Selection
Cauliflower
Brussels
Sprouts
Broccoli
Kohlrabi
Ancestral
Species
Kale
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15-3 Darwin Presents His Case
Evolution by Natural Selection
Evolution by Natural Selection
Darwin compared processes in nature to artificial
selection.
By doing so, he developed a scientific hypothesis
to explain how evolution occurs.
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Evolution by Natural Selection
The Struggle for Existence
Darwin realized that high birth rates and a
shortage of life's basic needs would force
organisms to compete for resources.
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Evolution by Natural Selection
The struggle for existence means that members of
each species compete regularly to obtain food, living
space, and other necessities of life.
The struggle for existence was central to Darwin's
theory of evolution.
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15-3 Darwin Presents His Case
Evolution by Natural Selection
How is natural selection related to a
species' fitness?
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Evolution by Natural Selection
Survival of the Fittest
The ability of an individual to survive and
reproduce in its specific environment is fitness.
Darwin proposed that fitness is the result of
adaptations.
An adaptation is any inherited characteristic that
increases an organism's chance of survival.
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15-3 Darwin Presents His Case
Evolution by Natural Selection
Successful adaptations enable organisms to become
better suited to their environment and better able to
survive and reproduce.
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15-3 Darwin Presents His Case
Evolution by Natural Selection
Individuals with characteristics that are not well suited
to their environment either die or leave few offspring.
Individuals that are better suited to their environment
survive and reproduce most successfully.
Darwin called this process survival of the fittest.
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Evolution by Natural Selection
Because of its similarities to artificial selection,
Darwin referred to the survival of the fittest as
natural selection.
In natural selection, the traits being selected
contribute to an organism's fitness in its
environment.
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Evolution by Natural Selection
Over time, natural selection results in
changes in the inherited characteristics
of a population. These changes
increase a species' fitness in its
environment.
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Evolution by Natural Selection
Descent With Modification
Natural selection produces organisms that have
different structures, establish different niches, or
occupy different habitats.
Each living species has descended, with changes,
from other species over time.
Darwin referred to this principle as descent with
modification.
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Evolution by Natural Selection
Descent with modification implies that all living
organisms are related to one another.
This is the principle known as common descent.
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15-3 Darwin Presents His Case
Evidence of Evolution
What evidence of evolution did Darwin
present?
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Evidence of Evolution
Evidence of Evolution
Darwin argued that living things have
been evolving on Earth for millions of
years. Evidence for this process could
be found in the fossil record, the
geographical distribution of living
species, homologous structures of
living organisms, and similarities in
early development, or embryology.
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Evidence of Evolution
The Fossil Record
Darwin saw fossils as a record of the history of life
on Earth.
By comparing fossils from older rock layers with
fossils from younger layers, scientists could
document that life on Earth has changed over time.
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15-3 Darwin Presents His Case
Evidence of Evolution
Geographic Distribution of Living Species
Darwin decided that all Galápagos finches could
have descended with modification from a common
mainland ancestor.
Darwin’s theory was that species now living on
different continents had each descended from
different ancestors.
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Evidence of Evolution
However, because some animals on each continent
were living under similar ecological conditions, they
were exposed to similar pressures of natural
selection.
Because of these similar selection pressures,
different animals ended up evolving certain features
in common.
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Evidence of Evolution
Similar, But Unrelated
Species
and
and
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15-3 Darwin Presents His Case
Evidence of Evolution
Homologous Body Structures
Structures that have different mature forms but
develop from the same embryonic tissues are
called homologous structures.
Similarities and differences in homologous
structures help biologists group animals according
to how recently they last shared a common
ancestor.
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Evidence of Evolution
Homologous Structures
Turtle
Alligator
Bird
Mammal
Ancient, lobefinned fish
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Evidence of Evolution
Not all homologous structures serve important
functions.
The organs of many animals are so reduced in size
that they are just vestiges, or traces, of homologous
organs in other species.
These organs are called vestigial organs.
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Evidence of Evolution
Similarities in Embryology
The early stages, or embryos, of many animals
with backbones are very similar.
The same groups of embryonic cells develop in the
same order and in similar patterns to produce the
tissues and organs of all vertebrates.
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Summary of Darwin's Theory
Summary of Darwin's Theory
Individual organisms differ, and some of this
variation is heritable.
Organisms produce more offspring than can
survive, and many that do survive do not
reproduce.
Because more organisms are produced than can
survive, they compete for limited resources.
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Summary of Darwin's Theory
Individuals best suited to their environment survive
and reproduce most successfully.
These organisms pass their heritable traits to their
offspring. Other individuals die or leave fewer
offspring.
This process of natural selection causes species to
change over time.
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Summary of Darwin's Theory
Species alive today are descended with modification
from ancestral species that lived in the distant past.
This process, by which diverse species evolved from
common ancestors, unites all organisms on Earth
into a single tree of life.
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Strengths and Weaknesses of
Evolutionary Theory
Strengths and Weaknesses of Evolutionary
Theory
Scientific advances in many fields of biology,
geology, and physics have confirmed and expanded
most of Darwin’s hypotheses.
Evolutionary theory continues to change as new
data are gathered and new ways of thinking arise.
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The scientist who motivated Darwin to publish
On the Origin of Species was
a. Alfred Russel Wallace.
b. Charles Lyell.
c. Jean-Baptiste Lamarck.
d. Thomas Malthus.
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Differences among individuals of a single
species are referred to as
a. artificial selection.
b. genetic variation.
c. survival of the fittest.
d. environmental adaptation.
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Changes that increase a species' fitness in its
environment over time are due to
a. the principle of common descent.
b. the geographic distribution of that species.
c. natural selection.
d. habitat selection.
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An inherited characteristic that increases an
organism's chance of survival is called a(an)
a. homologous structure.
b. vestigial organ.
c. adaptation.
d. analogous structure.
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Evidence used by Darwin to support the idea of
evolution included all the following EXCEPT
a. fossils that demonstrate change over time.
b. the genetic mechanism by which useful traits
are inherited.
c. the geographic distribution of living things.
d. the presence of many homologous
structures in plants and animals.
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END OF SECTION