Theory of Acquired Characteristics:
• An organism changes to adapt to its
environment and those changes are passed
on to its offspring.
• He thought that an organism’s actions
resulted in changes that could be inherited
by the next generation
• Although his ideas were not correct, Lamarck
introduced the idea of a scientific explanation
for evolution. Other scientists began to try
to explain it.
Charles Darwin (English Naturalist)
1831 – HMS Beagle
Collected rock, fossil, plant, and
animal specimens during the ship’s
travels to S. America.
• Charles Lyell
Who was Charles Lyell?
Lyell was a geologist who published a
book that suggested that the Earth was
millions of years old
• Before it was thought that Earth was
thousands of years old
• Lyell said that the age of the Earth had to be
judged by events that are happening now,
earthquakes, volcanic eruptions, floods
Who was Malthus?
Malthus was an economist who
published a book that said that if the
population of the world continued to
increase at is current rate, we would
run out of food and other resources
• Darwin thought that is that was true of
humans, it would also be true of nature
Galapagos Islands – a series of volcanic
islands off the coast of Ecuador
Why were the Galapogos
Islands important to Darwin?
Darwin saw organisms that were
similar to organisms he saw in South
Darwin saw somewhat similar species
on each island that were suited to their
• Darwin’s finches
• Galapagos Tortoises
What did Darwin observe about
the finches on the islands?
Darwin observed that the finches had
different shaped beaks
The beaks of the birds were adapted
to the food in the environment where
Darwin later found out that all the
birds were related and there were
similar birds living in South America
The Origin of Species
1859 – Darwin put together the evidence
for natural selection as a mechanism of
evolution and published The Origin of
Species (by Means of Natural Selection)
• The diverse forms of life have arisen by
descent with modification from ancestral
• The mechanism of modification has been
natural selection working over enormous tracts
Darwin used the term evolution only on
the last page.
How did his voyage influence
his idea of natural selection?
Darwin observed similar species
geographically close together
He observed similar organisms that
had adapted to different
• He inferred that the organisms has a
common ancestor and through natural
selection had adapted to their
Principles for Change Over Time:
1. Genetic variations within a population
2. Variations can be inherited.
3. Overpopulation “struggle for
4. Variations that increase reproductive
success (fitness) will have a greater
chance of being passed on than those
Theory of Natural Selection:
• Hypothesized that new species could appear
gradually over time through small changes in
Artificial Selection – Darwin
realized that the process of artificial
selection that was used in agriculture
and breeding of domestic animals
changed the characteristics of those
organisms. By selecting the parents
of the organisms the breeder can
choose the characteristics of the
Natural selection - Darwin inferred
that the same process could happen
in nature. The environment selects
which organisms are best suited and
those get to produce offspring.
If given enough time, natural
selection could modify a population
enough to produce a new species.
What is Evolution?
- Any change in the relative frequencies of alleles
in a population’s gene pool.
- Small changes over a long period of time
- Evolution works on populations not individuals.
- Evolution is CHANGE OVER TIME
Support for Evolution
1. Fossil Record:
How does fossil evidence
support Darwin’s ideas?
Fossils show that ancient species
shared similarities with species now
The fossil evidence is a visual time
table of how species have changes
2. Comparative Anatomy - study of similarities and
differences in the anatomy (body plan) of an organism:
a. Homologous Structures – anatomically similar
structures inherited from a common ancestor.
b. Vestigial Structures – structures that are the
reduced forms of functional structures in other
organisms. (see Table 15.2, page 425)
c. Analogous Structures – not inherited through
Examples of Vestigial Structures:
The wings of kiwis
are too small to be
of any use in flight.
Appendix Snake Pelvis
Examples of Analogous Structures:
Wing of an eagle and the wing
of a beetle have the same
function but are constructed in
different ways from different
3. Comparative Embryology – vertebrae
embryos exhibit homologous structures during
certain phases of development but become
totally different structures in the adult form.
2. Pharyngeal Pouches
Bird Embryo Human Embryo
4. Comparative Biochemistry – scientific
data shows that common ancestry can
be seen in metabolic molecules that are
- cytochrome c (see Fig. 15.9, page 427)
- other proteins, as well
5. Geographic Distribution
(biogeography)– of plants and animals
- Darwin observed that animals on the S.
American mainland were more similar
to other S. American animals than they
were to animals living in similar
environments in Europe.
Patterns of Evolution
1. Adaptive Radiation
3. Convergent Evolution
1. Adaptive Radiation
Also called divergent evolution
Can occur in a relatively short period of
When one species gives rise to many in
response to the creation of a new habitat
or another ecological opportunity.
Differences accumulate between
populations that result in new species
Organisms have a common ancestor
Example =Darwin’s finches
Many species evolve in close
relationship with other species.
The evolution of one species can
affect the evolution of another
Example = comet orchids and the
moths that pollinate them. The foot-
long flowers of this plant perfectly
match the foot-long tongue of the
3. Convergent Evolution
When unrelated species evolve
similar traits even though they live in
different parts of the world.
Organisms do not have a common
Occurs in environments that are
geographically far apart but that
have similar ecology and climate.
Example for convergent evolution:
Why does evolution matter