Download CHARLES DARWIN AND EVOLUTION I. Geologists have been able

CHARLES DARWIN AND EVOLUTION
I. Geologists have been able to illustrate that the Earth is more than 4.6 billion years old.
A. Fossils indicate that the first living cells on this planet appeared about 3.7 billion years ago.
1. These first cells were simple, prokaryotic organisms.
2. Eukaryotic cells first appear in fossils that date back about 1.5 billion years.
II. EARLY SCIENTISTS AND THEIR VIEWS OF THE EARTH AND PLANTS AND ANIMALS
A. George-Louis Leclerc (Count Buffon)-1707-1788-A French Naturalist. He wrote works that
indicated that plants and animals were influenced by the environment in which they live.
B. Georges Cuvier-1769-1832-Zoologist who developed the science of paleontology.
1. What is paleontology?
2. He believed in the fixity of species and he proposed the idea that catastrophes occurred
in history to destroy plant and animal populations. Following the catastrophes, new
species were created. This explanation is known as catastrophism.
C. Jean-Baptiste de Lamarck-1744-1829-believed that the environment could bring about
inherited change. This is known as the idea of Inheritance of Acquired Characteristics.
1. Can you think of an example to illustrate this concept?
D. Charles Lyell-1791-1875. Famous geologist who supported the idea that the Earth was subject
to slow but continuous cycles of change. He supported the view that the Earth’s physical
features were produced over millions of years.
E. Thomas Malthus-an English economist. He argued that populations produce far more
organisms than can actually survive. In other words, some individuals will not be able
to survive.
III. CHARLES DARWIN (1809-1882)-an English Naturalist.
A. 1831-Darwin, at the age of 22, accepts a position aboard the HMS Beagle. This British Naval
ship was commissioned to sail around the world.
1. Darwin’s job on this ship was to examine the various land masses that the ship passed
for natural resources (water, food, gold etc...).
2. The ship was ordered on a 5 year voyage.
3. On the journey, Darwin had the opportunity to examine plants and animals that lived
in the areas that the ship passed by. He also had the opportunity to collect specimens
and fossils during the journey.
B. The Galapagos Islands-volcanic islands located off of the Pacific coast of South America.
1. Darwin noticed that the species of plants and animals on these islands were different
from the species he had observed on the South American mainland.
2. Tortoises-Darwin noticed that each island seemed to have its own specific type(s) of
tortoises.
a. Long neck tortoises were common on dry islands. The neck apparently helped
the tortoises to reach cacti.
b. Tortoises with shorter necks were found on islands that received more rainfall.
3. Finches-today, these are known as Darwin’s Finches.
a. Again, Darwin noticed major differenced between the finches of the different
Galapagos Islands.
b. What kinds of differences did he observe in these birds?
C. Darwin observed similar patterns among a variety of plants and animals in the Galapagos.
D. When Darwin returned to England, he continued to read his notes along with texts that
described processes that influenced the development of the Earth.
E. On The Origin of Species-book written by Darwin in 1858.
1. Key Points in the Book:
a. Evolution-defined by Darwin as “decent with modification.” Essentially
what he was saying was that species change with time. According to Darwin,
this would account for the great diversity of life on Earth.
b. Evolution occurs through a process Darwin referred to as Natural Selection.
c. Key Points on Natural Selection
1) The members of a population have heritable differences.
2) In a population, more individuals are produced than can survive.
a) Where did Darwin get this idea from?
3) Some individuals have characteristics that allow them to live and
survive successfully in their particular habitat. Those without these
traits will not survive. What did Darwin call this principle?
4) Over time, positive traits are passed on to offspring, who will live
and flourish in their environment.
5) Over time, more individuals with positive traits will survive and
appear in a population.
6) The result is a population that is adapted to its local habitat.
d. Species become adapted to their habitat.
e. Overall, Darwin’s key point was that POPULATIONS evolve over time
so they can best use the available resources for survival.
2. What was not covered in the book?
a. Darwin made no mention of the creation of life (or where did life come
from).
b. He made no comments about genetics. Remember, Darwin was doing his work
prior to Mendel’s discovery of the modern principles of genetics. As a matter
of fact, Mendel’s work and Darwin’s work were published just 7 days apart.
However, they did not know about the others work.
3. What did Darwin use as evidence in his book?
a. The Fossil Record
b. The distribution of plant and animal species-most organisms are highly
adapted for the habitat that they live in.
c. Comparative anatomy
d. Taxonomy
e. Comparative embryology
f. Artificial selection
4. Today, evolutionists are looking at the above areas along with: genetic studies,
behavioral studies, physiological studies and molecular studies.
5. Alfred Russel Wallace-provided substantial support for Darwin’s Theory of Evolution.
a. He formulated many of the same conclusions as Darwin. Wallace did he
research on insects.
IV. A CLOSER LOOK AT THE EVIDENCE FOR EVOLUTION
A. Fossils-these are the partially preserved remains of a once living organism.
1. These found in soil or sediments.
2. Sediments of the same age contain similar species of plants and animals.
a. Older sediments contain fossils of prokaryotic cells and early eukaryotes.
b. Simple multicellular organisms come next.
c. Trilobites and other invertebrates followed.
d. Fish appear next in fossil evidence.
e. Amphibians followed.
f. Reptiles appeared after the amphibians.
g. Dinosaurs, crocodiles, birds and mammals appeared in higher levels of
sediments.
3. There is a great deal of consistency in the above appearance of organisms. That is,
soils that contain trilobites never contain dinosaur fossils.
4. This appearance of organisms fits well with The Theory of Evolution.
5. Fossils can also be accurately dated using Carbon 14 Dating.
a. This has shown that fossils from deep sediments are the oldest.
6. Problems with Fossils:
a. Not all things form fossils. Typically, only hard structures can fossilize.
b. The fossil record is incomplete.
B. Comparative Anatomy
1. Homologous structures-structures with a common ancestry that have evolved different
functions over time.
2. Analogous structures-structures that evolved similar functions but do not share a
common ancestor.
a. What would be an example of an analogous structure?
3. Vestigial structures-structures that are fully developed in one group of organisms but
that are reduced and possible nonfunctioning in another group.
a. Examples in animals:
1) The splint-
2) Bird wings-
b. Examples of Vestigial Structures in Humans:
C. Comparative Embryology
1. Most animals have similar patterns of embryological development. All vertebrates
have almost identical patterns of development. This itself indicates a similar ancestry.
D. Genetic/Molecular Comparisons
1. Scientists are now examining the DNA of living organisms. They are comparing DNA
of modern groups of organisms with the DNA of earlier specimens. They are searching
for similar genes.
2. The molecular record indicates that there are several patterns of evolution.
3. Scientists also examine proteins that living organisms produce. Many species produce
similar proteins, so researchers look for how many related proteins organisms produce
to examine similarities.
4. The evolutionary history of DNA sequences and proteins agrees almost perfectly with
the similarities observed in the fossil record.
5. Molecular studies have also indicated mutations that have occurred over time. These
studies have shown when the mutation occurred and in which gene it occurred in.
E. Biogeography-the study of the distribution of species.
1. Darwin suggested that species would be most closely related to those that live nearby,
not organisms that live in exactly the same habitats in other parts of the world.
2. Example:
V. FACTORS THAT INFLUENCE EVOLUTION
A. Mutation-any change in DNA. These changes can be helpful or harmful, depending on the
change. Example of a mutation:
B. Migration-
1. This can alter the genetic makeup of a particular population. Migration can add or
remove genes from a population.
C. Genetic Drift-a change in gene frequency that occurs by chance alone.
1. 2 Examples of Genetic Drift:
a. The Founder Effect-occurs when a few individuals leave a population and
form a new, isolated population. Example:
b. The Bottleneck Effect-the sudden loss of a large number of individuals in a
population.
1) Genes may be lost in the population.
2) This may lead to extinctions.
3) What can cause this to occur?
VI. SPECIATION-
A. Species-a group of potentially interbreeding populations that are reproductively isolated from
other such groups. Species are often divided into subspecies.
B. 2 Types of Speciation:
1. Allopatric Speciation-occurs due to geographic isolation.
2. Sympatric Speciation-occurs without geographic isolation.
VII. CONTINENTAL DRIFT (PLATE TECTONICS)-proposed by Alfred Weggner in 1915.
A. According to Weggner, all of the continents were once hooked together to form a
supercontinent known as Pangea. Over time, this large land mass broke apart and
the land masses moved to form the present day continents.
1. He suggested that this must be the case since it appeared that several of the
continents all hooked together.
2. This proposal gained very little support when it was proposed.
3. Why was this idea not accepted in Weggner’s day?
B. In the 1960’s, scientists were able to prove that the continents actually sit on plates that
can slide past each other over time. This means that the continents can and do move. This
discovery helped to revive Weggner’s proposal.
C. Continental Drift
1. 200 million years ago, the continents were hooked together into one large land mass
known as Pangea.
2. By 180 million years, Pangea had split into 2 land masses known as Laurasia and
Gondwanaland. These two land masses continued to split and the land masses moved
to form the current position of the continents (this occurred by about 75 million years
ago).
D. Proof/Evidence for Continental Drift
E. Fossil evidence indicates that evolution occurred as the continents moved over time.
VIII. PATTERNS OF SELECTION
A. Directional Selection-shift allele frequency so that phenotypes at one end of a range become
more abundant over time.
B. Stabilizing Selection-occurs when an intermediate form of a trait is favored against the
extreme forms.
C. Disruptive Selection-condition that favors traits at both ends of the range.
IX. REPRODUCTIVE ISOLATION-prevents reproduction between individuals; thus ending gene flow.
A. Mechanisms of Reproductive Isolation:
1. Temporal Isolation-populations cannot interbreed due to differences in timing of their
reproductive cycles.
2. Mechanical Isolation-populations cannot interbreed due to anatomical differences.
3. Ecological Isolation-populations cannot interbreed since they live in different habitats.
4. Behavioral Isolation-populations do not interbreed due to differences in their
behavioral patterns.
X. TERMS:
A. Phylogeny-the evolutionary history of a species or group of species.
1. Monophyletic group-an ancestor with all of its descendants.
B. Cladistics-making hypothesis about evolutionary relationships.
1. Cladogram-an “evolutionary tree.”
a. Can you read a Cladogram?