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Chapter 30
The Theory
of Evolution
http://www.pbs.org/wgbh/nova/odyssey/debate/
http://www.nationalgeographic.com/features/outpost/
http://www.discovery.com/news/features/humanorig
Evolution
• A process of change
through time
Theory of Evolution
1. Suggests that existing forms of life
on earth have evolved from earlier
forms over long periods of time
2. Evolution accounts for the
differences in structures, function,
and behavior among life forms as
well as changes that occur in
populations over many generations
(I) Evidence of Evolution
• Observations supporting the theory
of organic evolution can be made
through the study of:
1. Geologic record
2. Comparative Cytology,
Biochemistry, Anatomy, and
Embryology
(A) Geologic Record
1. Earth is between 4.5 to 5 billion
years old (age was determined by
radioactive dating of rocks)
2. Fossils- are the remains of traces of
organisms that no longer exist.
Fossils have been preserved in ice,
sedimentary rock, amber, and tar
Archaeopteryx
Tyrranosaurus rex
3. Other fossils have been formed from
petrification, a process by which the tissues are
gradually replaced by minerals that produce a
stone replica of the original material
4. Imprints, casts, and molds of organisms or parts
of organisms are frequently found in sedimentary
rock
5. In undisturbed layers (strata) of sedimentary
rock, the lower strata contain old fossils while the
upper strata contain younger fossils
(B) Comparative Anatomy
1. Evidence supports that
similarities of basic
structures exist between
different organisms
2. Homologous structures
are anatomical parts
found in different
organisms in origin and
structure
3. The presence of such
homologous structures
suggest that these
organisms have evolved
from a common ancestor
(B) Comparative Anatomy
Homo sapiens
Paranthropus boisei
(C) Comparative Embryology
• Although certain adult
organisms may be
different from each
other, a comparison of
the earl stages of their
embryonic
development may
show similarities that
suggest a common
ancestor
(C) Comparative Embryology
(D) Comparative Cytology
1. All living things are made up of cells
2. Cell organelles including the cell
membrane, ribosome's, and
mitochondria are structurally and
functionally similar in most
organisms
Mitochondrion DNA and can
replicate
(E) Comparative Biochemistry
• All living things contain similar
biochemical compounds
• Examples would include: structure
and function of DNA, RNA, and
proteins (including enzymes) are
similar in all organisms
(II) Theories of Evolution
1. Attempts to explain the similarities
and differences among species
2. Adaptations- are a major component
to these theories. Adaptations are
features which make a species better
suited to live and reproduce in its
environment
(A) Jean Baptiste Lamark
(A)
Lamark
• The evolutionary theory of Jean-Baptiste
Lamark was based on the principle of:
1. Use and Disuse
2. Inheritance of acquired traits
Principle of Use and Disuse
• For an organism, new structures appeared
in the course of evolution because they were
needed. Structures that were present and
were used became better developed and
increased in size; structures that were not
used decreased in size and eventually
disappeared
Ex: muscles of an athlete vs. appendix
Inheritance of Acquired Traits
• Useful characteristics acquired by an
individual during its lifetime can be
transmitted to its offspring
• These acquired traits results in species
that are better adapted to their
environment
• Ex: a giraffe’s neck became longer as a
result of stretching to reach higher
branches. This acquired trait was then
passed down to the offspring
Inheritance of Acquired Traits
Arnold’s kids wouldn’t be “pumped”
(B)
Weisman
1. August Weisman did not agree with
Lamark’s theory of acquired traits
2. In a series of experiments, Weisman removed
the tails of mice
3. The mating of these tailless mice produced
offspring with tails of normal length
4. Weisman removed the tails of these mice and
allowed them to mate
5. Again, offspring were produced with tails of
normal length
6. The acquired condition of “taillessness” was
not inherited
(C)
Charles Darwin
C) Darwin’s Ship the HMS Beagle
(C)
Darwin
• Charles Darwin devised a theory of evolution
based on variation and natural selection as seen
in the Galapagos islands.
• Included in hid theory were five main ideas:
1. Overpopulation
2. Competition
3. Survival of the Fittest
4. Reproduction
5. Speciation
Overpopulation
• Within a population, there
are more offspring produced
in each generation than can
possibly survive
Competition
• Natural resources; like food,
water, and space available to a
population is limited
• Because there are many
organisms with similar
nutritional requirements, there
must be competition between
them for the resources needed to
survive
Survival of the Fittest
• Variations among
members of a population
make some of them better
adapted to the
environment than others
• It is generally the bestadapted individuals that
will survive
• The environment is the
agent of natural selection
determining which
species will survive
Reproduction
• Individuals that survive and
then reproduce transmit these
variations to their offspring
Speciation
• The development of a new species
occurs as variations or adaptations
accumulate in a population over
many generations
• Ex: caveman Æ present man
Speciation “El Chupacabra”
Speciation
What is El Chupacabra?
El Chupacabra - Means "the goat sucker" in Spanish.
Named because of the way it sucked all the blood from Puerto
Rican goats, the Chupacabra has been leaving fear in its tracks
for many years now.
Speciation “Bigfoot? Sasquatch?
(III) Modern Theories of Evolution
• The modern theory of evolution
includes both Darwin’s ideas of
variation and natural selection
and the current knowledge of the
sources of variations
(A) Sources of Variations
1. Segregation and the
recombination of alleles during
sexual reproduction
2. Gene mutation occurs
spontaneously and at random
(B) Natural Selection
1. Natural selection involves the struggle of organisms to
survive and reproduce in a given environment
2. Traits which are beneficial to the survival of an
organism in a particular environment tend to be
retained and passed on, and therefore, increase in
frequency within a population
3. Traits which have low survival value to an organism
tend to diminish in frequency from generation to
generation
4. If environmental conditions change, traits that have
low survival value may now have a greater survival
value. Therefore, traits that prove to be favorable
under new environmental conditions will increase in
frequency
Ex: Insects resistant to insecticides
1. Genetic make-up of some insects make them resistant
to the effects of insecticides
2. Before the widespread use of insecticides, this trait was
of no particular survival value
3. With the increased use of insecticides, this trait
developed a very high survival value
4. Therefore, insects with resistance to insecticides
survived and reproduced much more successfully than
those lacking the trait
5. As a result, the frequency of insecticide resistance has
increased greatly in insect populations
(C) Geographic Isolation
Gene frequency- the percentage of organisms in a
population that carry an allele
1. Isolation of a population increases the chances for
speciation (the development of a new species) by
separating a small group of organisms from the main
population with its large gene pool (inheritable traits)
2. Changes in gene frequency are more likely to occur in
small populations than in large ones
3. Geographic isolation of a population is caused by
natural barriers like mountains, large bodies of water,
and deserts
•
(C) Geographic Isolation
(C) Geographic Isolation
4. The evolution of an isolated population into a
new species may involve the following factors:
a) the gene frequency in the isolated population
may have been different than the gene frequency
in the main population to begin with
b) different mutations occur in the isolated
population and in the main population
c) different environmental factors may also have
exerted different selection pressures on each
population (natural selection was different)
(D) Reproductive Isolation
• If the isolated population becomes so
different from the main population that
members of the two cannot interbreed and
produce fertile offspring, then they have
become two distinct species
(E) Time Frame for Evolution
• There are two different theories proposed
by scientists to address the rate of
evolution:
1. Gradualism- proposes that evolutionary
change is slow, gradual, and continuous
2. Punctuated Equilibrium- proposes that
species have long periods of stability
(several million years) interrupted by
geologically brief periods of significant
change during which a new species may
evolve
(IV) Heterotroph Hypothesis
• Is one proposed explanation for how
life arose and evolved on primitive
earth
• According to this hypothesis, the first
life forms were heterotrophic and had
to obtain their nutrients from the
environment
(A)
Primitive Earth
• Based on assumption
1. Earth was very hot consisting of inorganic
substances in all states: solid, liquid, and gas
2. Many sources of energy including heat,
lightning, solar radiation(x-rays and U.V. rays),
and radiation from radioactive rocks
3. The atmosphere consisted of water vapor,
hydrogen, methane gas, and ammonia
4. As the earth cooled, water condensed in the
atmosphere and rain fell forming seas described
as “hot, thin soup”
Stanley Miller’s experiment
(B) Synthesis of Organic Compounds
1. In the seas, (primordial soup) chemical bonds
formed between the dissolved substances
2. Eventually, various types of organic molecules
formed in the seas, including amino acids and
simple sugars
3. More complex organic compounds were then
formed by the interactions between the
simpler molecules
(C)
Nutrition
1. Some of the large. Complex molecules
formed groupings or clusters called
aggregates
2. These aggregates developed a surrounding
“membrane”
3. It is believed that aggregates absorbed
simple organic molecules from the
environment for food
4. Therefore, they carried on a form of
heterotrophic nutrition
(D)
Reproduction
1. In time, as these aggregates became more
complex and highly organized, they
developed the ability to reproduce
2. At the point where the ability to reproduce
had evolved, the aggregates were
considered to be living cells
(E) Heterotroph to Autotroph
1. It is thought that these early heterotrophic life
forms carried on a form of anaerobic
respiration known as fermentation
2. As a result of the extended periods of
fermentation, carbon dioxide was added to the
atmosphere
3. Eventually, as a result of evolution, some
heterotrophic forms developed the capacity to
use carbon dioxide from the atmosphere to
form organic compounds (food)
4. These organisms were the first autotrophs
(F) Anaerobes to Aerobes
1. Autotrophic activity (photosynthesis) added
free oxygen to the atmosphere
2. Over time, the capacity to use oxygen in
respiration (aerobic) evolved in both autotrophs
and heterotrophs
3. Present day organisms may be heterotrophic or
autotrophic; aerobic or anaerobic
http://biog-101-104.bio.cornell.edu/biog101_104/biog102/miller_expt.html