Download Chapter 14

Essentials of Biology
Sylvia S. Mader
Chapter 14
Lecture Outline
Prepared by: Dr. Stephen Ebbs
Southern Illinois University Carbondale
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
14.1 Darwin’s Theory of
Evolution
• Charles Darwin’s derived his theory of
evolution in part from observations he
made while serving as the naturalist
aboard the HMS Beagle.
14.1 Darwin’s Theory of
Evolution (cont.)
Before Darwin
• Prior to Darwin’s theories, there were
different views of the world and living
organisms.
Before Darwin (cont.)
Before Darwin (cont.)
• The research of several scientists helped
change the world’s perception of the world
and living organisms.
• Zoologist Georges Cuvier, who founded
the field of paleontology, suggested that
catastrophes were responsible for the
drastic changes in living organisms over
time.
Before Darwin (cont.)
Before Darwin (cont.)
• Jean-Baptiste de Lamarck offered
explanations for the changes in organisms
between strata.
– Evolution occurred as the environment forced
organisms to adapt.
– These adaptations caused less complex
organisms to evolve into more complex
organisms.
– Adaptation occurs because of the use or
disuse of a structure, an element of the theory
of acquired characteristics.
Before Darwin (cont.)
• Darwin’s ideas were similar to those of
Lamarck, but with important differences.
– Darwin believed that living things share
common characteristics because they have a
common ancestor.
– Darwin also believed that the organisms
adapt to the environment, but through a
process called natural selection.
Darwin’s Conclusions
• Darwin’s conclusions were based upon his
study of geology, fossils, and
biogeography.
Darwin’s Study of Geology and
Fossils
• Geological theories contributed to Darwin’s
efforts.
• James Hutton proposed that the Earth
undergoes slow, continuous cycles of erosion
and uplifting.
• Erosion deposits thick layers of sediment, which
eventually form sedimentary rocks.
• The uplifting of sedimentary rock forms new land
and can expose fossils.
Darwin’s Study of Geology and
Fossils (cont.)
Darwin’s Study of Geology and
Fossils (cont.)
Darwin’s Study of Geology and
Fossils (cont.)
• Lyell proposed the theory of
uniformitarianism, which maintained that
extreme geological changes could be
caused by slow, natural processes.
• This theory also suggested that the Earth
must be very old, much older than most
believed.
Darwin’s Study of Geology and
Fossils (cont.)
• Darwin observed similar geological
changes and collected fossils during his
time on the Beagle.
• These activities caused Darwin to accept
the fact that the Earth was very old.
• From this, Darwin proposed that modern
organisms may have descended from now
extinct organisms.
Darwin’s Study of Geology and
Fossils (cont.)
Darwin’s Study of Biogeography
• Darwin made extensive comparisons
between similar animals from around the
world to understand evolution.
• He postulated that similar environments
may have caused convergent evolution, or
the development of similar adaptations.
Darwin’s Study of Biogeography
(cont.)
Darwin’s Study of Biogeography
(cont.)
• When Darwin’s ship reached the
Galapagos Islands, he noticed that the
finches had greatly diversified.
• The finches had different beak structures
as well as different feeding habits.
Darwin’s Study of Biogeography
(cont.)
Darwin’s Study of Biogeography
(cont.)
• From his observation of the Galapagos
finches, Darwin postulated that speciation
had occurred.
• Speciation is the process by which
different groups of an organism evolve
independently from one another, ultimately
becoming a different species.
Natural Selection and
Adaptation
• Darwin suggested that natural selection was the
process that caused adaptation.
• The process of natural selection has several
preconditions that must be met.
– The members of a population show variation.
– More individuals are born in a population than die.
– Some individuals inherit adaptive characteristics that
favor their survival and reproduction.
Natural Selection and
Adaptation (cont.)
Natural Selection and
Adaptation (cont.)
• If the preconditions are met, natural
selection has consequences.
– In each generation, an increasing number of
individuals have the adaptive characteristics.
– Natural selection adapts a population to its
local environment.
• Natural selection relies on the variations
produced by genetic changes.
Organisms Have Variations
• Prior to Darwin, variation within a
population was ignored.
• Darwin argued that the random
occurrence of these variations was
essential to natural selection.
• These variations that allow for adaptation
to the environment must also be heritable.
Organisms Struggle to Exist
• Thomas Malthus believed that death and
famine were inevitable because human
population increases faster than food
supplies.
• Darwin used this concept to argue that
available resources were insufficient to
allow all members of a population to
survive.
Organisms Struggle to Exist
(cont.)
• Thus there is a constant struggle to obtain
the resources needed to survive and
reproduce.
Organisms Differ in Fitness
• Those organisms best capable of obtaining the
resources necessary to survive and reproduce
are those with the greatest fitness.
• The character that determines whether an
organism is fit varies from population to
population.
• When humans carry out artificial selection,
breeders select specific traits that are favorable.
Organisms Differ in Fitness
(cont.)
• The concepts of natural selection and
fitness argue that interaction with the
environment and random variation are
responsible for evolution.
• This differs from the theory of acquired
characteristics proposed by Lamarck.
Organisms Differ in Fitness
(cont.)
Organisms Become Adapted
• The consequence of natural selection and
fitness is that organisms adapt to their
environment.
• The adaptations that make organisms more
suited to the environment can occur
simultaneously in different species.
• Convergent evolution occurs when different
organisms acquire similar adaptations.
Organisms Become Adapted
(cont.)
Evidence for Evolution
• According to the theory of evolution,
organisms descend from a common
ancestor but adapt to particular
environments.
• There are several lines of evidence that
support the theory of evolution.
Fossil Evidence
• The fossil record contains rich information
about the life on Earth >10,000 years ago.
• One piece of evidence provided by the
fossil record is that the pattern of evolution
is typically from simple to more complex.
• The fossil record also reveals transitional
links between different organismal groups.
Fossil Evidence (cont.)
Biogeographical Evidence
• Biogeography is the study of the distribution of
plants and animals throughout the world.
• While there are many similar environments
around the world, the plants and animals that
live there are often unique.
• The different organisms must have arisen from
different evolutionary events.
Biogeographical Evidence
(cont.)
Anatomical Evidence
• Darwin and others have also showed that
different species share vestigial structures that
reveal their common descent.
– Whales and snakes all show vestigial bones related
to four-legged animals.
– Humans have a tailbone but not tail.
• Organisms may also have homologous
structures, which are anatomically similar
structures that reveal common ancestry.
Anatomical Evidence (cont.)
Anatomical Evidence (cont.)
• In contrast, organisms may have
analogous structures, which have a similar
function but are derived differently
evolutionarily.
• The homology of all vertebrates can be
seen in the similarities in embryonic
development.
Anatomical Evidence (cont.)
Biochemical Evidence
• The study of biochemistry and genetics
has shown that many organisms use
similar chemicals and genes.
• The diversity in living organisms is due to
slight differences in this set of genes.
Biochemical Evidence (cont.)