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Chapter 30
process of change
through time.
Theory of Evolution
Suggests that existing forms of life
on earth have evolved from earlier
forms over long periods of time.
Evolution accounts for the
differences in structures, function,
and behavior among life forms as
well as changes that occur in
populations over many generations.
Pinocchio frog
(I) Evidence of Evolution
supporting the
theory of organic evolution can
be made through the study of:
1. Geologic record
2. Comparative Cytology,
Biochemistry, Anatomy, and
(A) Geologic Record
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.
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
Petrified National Forest in
(B) Comparative Anatomy
Evidence supports that similarities of basic
structures exist between different organisms.
2. Homologous structures are anatomical parts
found in different organisms in origin and
3. The presence of such homologous structures
suggest that these organisms have evolved
from a common ancestor.
Difference between Analogous
and Homologous structures
(C) Comparative
Although certain
adult organisms
may be different
from each other, a
comparison of the
early stages of their
development may
show similarities
that suggest a
common ancestor.
(D) Comparative Cytology
All living things are made up of cells.
Cell organelles including the cell
membrane, ribosome's, and mitochondria
are structurally and functionally similar in
most organisms.
(E) Comparative Biochemistry
 All
living things contain similar biochemical
 Examples would include: structure and
function of DNA& RNA, and proteins
(including enzymes) are similar in all
(II) Theories of Evolution
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
(A) Lamark
 The
evolutionary theory of JeanBaptiste 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
 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 .
Lamarck's conception of evolution
(B) Weisman
August Weisman did not agree with Lamark’s
theory of acquired traits.
In a series of experiments, Weisman removed
the tails of mice.
The mating of these tailless mice produced
offspring with tails of normal length.
Weisman removed the tails of these mice and
allowed them to mate.
Again, offspring were produced with tails of
normal length.
The acquired condition of “taillessness” was
not inherited.
(C) Darwin
Charles Darwin devised a theory of evolution
based on variation and natural selection.
 Included in hid theory were five main ideas:
1. Overpopulation
2. Competition
3. Survival of the Fittest
4. Reproduction
5. Speciation
Natural Selection
Natural selection is the evolutionary
process which selects the variation(s)
of organisms best suited for a particular
Natural selection and its evolutionary
consequences provide a scientific
explanation for the fossil record of
ancient life, as well as for the molecular
and structural similarities observed
among the diverse species of living
3. The degree of kinship between
organisms or species can be
estimated from the similarity of their
DNA sequences; this similarity often
closely matches organisms' or
species' classification based on
anatomical similarities.
DNA Sequence Similarities in Some Primates
The graphic above shows that:
1.All of these primates had a common ancestor, the
ancestral primate.
2.The human and chimpanzee have the closest
evolutionary relationship as their DNA is the most similar.
a population, there are
more offspring produced in
each generation than can
possibly survive.
 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 best-adapted
individuals that will survive.
The environment is the agent of
natural selection determining which
species will survive.
 The
individuals who survive are the
ones best adapted to exist in their
environment due to the possession of
variations that best suit them to their
environment. This genetic variability
within a species is chiefly due to
mutation and genetic recombination.
The variation of organisms within a
species increases the likelihood that
at least some members of the species
will survive under
changed environmental conditions.
that survive and
then reproduce transmit
these variations to their
The development of a different
species occurs as variation or
adaptations accumulate in a
population over many generations.
 Ex: caveman  present man
• Small differences between parents and
offspring can accumulate in
successive generations so that
descendants become very different from
their ancestors.
• An adaptation is a variation which
assists an organism or species in its
•Biological adaptations include
changes in structures, behaviors,
or physiology that enhance survival
and reproductive success in a
particular environment.
 Some
characteristics give individuals
an advantage over others in surviving
and reproducing, and the advantaged
offspring, in turn, are more likely than
others to survive and reproduce. The
proportion of individuals that have
advantageous characteristics will
 Behaviors have evolved through natural
selection. The broad patterns of
behavior exhibited by organisms have
evolved to ensure reproductive success.
Modern Examples of Natural
Peppered moth:
• two varieties of peppered moth existed,
a light colored and a dark colored one
• as industrialization and coal burning
increased, the environment in England where
these moths lived became dirtier
• the dark colored variety of the moth blended
into the trees and increased in numbers, while
the light colored moth was less adapted and
decreased in numbers.
Insect resistance to insecticides:
Insecticides kill insects not resistant
to the insecticide, while insects
resistant to the insecticide live to
reproduce. The insecticide acts as a
selecting agent.
Bacterial resistance to antibiotics:
Bacteria not resistant to an antibiotic
are killed by it, while resistant bacteria
live to reproduce. The antibiotic is a
selecting agent for these bacteria.
(III) Evolution and Extinction
 Evolution
does not necessarily mean
long term progress is going to go in
a certain direction.
 Evolutionary changes often appear to be
like the growth of a bush. Some
branches survive from the beginning
with little or no change, many die out
altogether, and others branch out
repeatedly, sometimes giving rise to
more complex organisms.
Direction of Evolution
Note the divergence of the various groups from a
common ancestor and the fact that some branches
became extinct.
• Extinction of a species occurs when the
environment changes and the
adaptive characteristics of a species are
insufficient to allow its survival.
• The fossil record indicates that many
organisms that lived long ago are extinct.
• Extinction of a species is common; most
of the species that have lived on earth no
longer exist.
(IV) Modern Theories of
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
Segregation and the recombination of alleles
during sexual reproduction.
Mutations are random changes in the genes or
DNA of sex cells may result in new gene
combinations creating variation in the offspring
formed from these.
Only mutations that occur in sex cells can be
passed on to the offspring. Mutations which
occur in other cells can be passed on to other
body cells only.
The experiences an organism has during its lifetime
can affect its offspring only if the genes in its own sex
cells are changed by the experience.
1. Variation and Evolution
Evolution is the consequence of the
following factors:
1. The potential for a species to increase its
2. The genetic variability of offspring due to
mutation and recombination of genes
3. A finite supply of the resources required for
4. The ensuing selection by the environment of
those offspring better able to survive and
leave offspring.
 Some
characteristics give individuals
an advantage over others in
surviving and reproducing, and the
advantaged offspring, in turn, are
more likely than others to survive
and reproduce. The proportion of
individuals that have advantageous
characteristics will increase.
An Example of Variation Driving Natural Selection
Natural selection favors longer necks better chance to get
higher leaves. Favored character passed on to next generation.
Original group
exhibits variation
in neck length.
• The variation of organisms within a species increases the likelihood that at least
some members of the species will survive under changed
environmental conditions.
• The great diversity of organisms is the result of billions of years of selection for
favorable variations that has filled available niches of our planet with life forms.
(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
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.
(D) Reproductive Isolation
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
(E) Time Frame for Evolution
 There
are two different theories proposed
by scientists to address the rate of
1. Gradualism- proposes that
evolutionary change is slow, gradual, and
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
 Darwin's
studies of finches on the
Galapagos islands suggest that the
finches differences in beak structure
were most directly due to
Acquired characteristics in the parent
2. The size of the island where the finches
3. Mating behaviors of the different finches
4. Adaptations of the finches to different
Darwin’s theory of
evolution, he was not able to
 Darwin
proposed that organisms
produce many more offspring that can
possibly survive on the limited amount
of resources available to them.
According to Darwin, the offspring that
are most likely to survive are those that
Are born first and grow fastest
2. Are largest and most aggressive
3. Have no natural predators
4. Are best adapted to the environment
 One
concept that supports the theory of
evolution states that organisms best
adapted for survival are the ones that
will reproduce and pass traits on the
future generations. Adaptations that
can be passed on do not include
Basic structure of the organism
2. The reflex actions of the organism
3. The manner in which the organism carries
out respiration
4. Techniques for hunting food taught by the
parents of the organism
 According
to this information in the chart
that follows, the closest evolutionary
relationship most likely exists between
Human and chimpanzee
2. Human and gorilla
3. Chimpanzee and gorilla
4. Horse and zebra
or false – individuals with
advantageous adaptations to the
environment tend to increase in
 True
Artificial selection
Macroevolution – evolution
occurring on a large scale that
can be observed or witnessed.
Microevolution: Evolution
occurring on a small scale, not
enough to cause speciation but
enough to produce small
hypothesis: the
idea that the first organisms on
this earth were heterotrophic.
(Unable to synthesis their own organic molecules).
No true nuclear membrane
on the conditions of early
 Atmosphere
consisted of
 Hydrogen
 Water (H2O)
 Ammonia (NH3)
 Methane (CH4)
 Thunder storm with a lot of lightning
 These
gases dissolved in the oceans
making a hot thin soup of organic
 Moneran
 Prokaryotic
unicellular without nuclear membrane
 Anaerobic
most did not use Oxygen to undergo
respiration because there was not oxygen in
the beginning.
 Heterotrophic
Could not make their own food, but gave off
CO2 to atmosphere
 Autotrophs
Some adapted to use CO2, and were
photosynthetic giving off oxygen.
Who came first?
Heterotrophs or Autotrophs?
Stanley Miller