Evolution



Evolution

( )

• Theories of evolution assume that modern life forms have evolved

1. Evidence of Evolution

• Attempts to describe the mechanisms by which organisms change over time have formed the basis of the evolutionary theory.

[pic]

Theories of Evolution

• Attempt to explain the diversity of life forms on earth

• Species diversity is actually based on the variety of

• Adaptations - any structural, functional, or behavioral characteristic of a species that helps it to

Evidence of Evolution continued:

A. Comparative Cytology

• Organisms with very similar structures are usually

B. Comparative Biochemistry

• Analysis of enzymes and other proteins show that a great deal of similarity

[pic]

C. Comparative Anatomy

• Similar organisms can be shown to have limbs, internal organs, or other structures that are constructed similarly.

• These structures are known as

[pic]

D. Comparative Embryology

• Reproductive processes in many different organisms

[pic]

E. Geologic Record

• Fossils are commonly discovered in sedimentary rock layers.

[pic]

• The oldest fossil of the simplest life forms are generally found in the bottom layers. While the younger fossils of more complex organisms

• This is an example of relative dating.

[pic]

• Scientists can determine the age of fossils

F. Vestigial Structures: structures that do not seem to have any use (are also reduced in size) but are

• Human examples: appendix, tailbone (coccyx), wisdom teeth, muscles that move the ears and nose

• Animal examples: whales and pythons have vestigial hind leg bones embedded in body wall

[pic][pic]

[pic]

[pic]

C. Charles Darwin

-19th Century naturalist from England

-Devised a theory of evolution based

-His theory forms the basis of the

• Darwin’s Five Main Ideas:

1. Overproduction: species have a tendency to produce

2. Competition: Within each species there is a struggle for survival that may eliminate many

3. Variation: Darwin noticed variation within a species even though he could not explain it. He knew nothing of genes.

4. Survival of the Fittest: Animals better able to resist disease, withstand environmental conditions,

5. Reproduction: Adaptive advantages of one generation may be passed on to the next, perpetuating them in the species.

-This process is

D. Modern Evolutionary Theory

-Based primarily on

-In addition it incorporates the information available from

Five Main Ideas:

1. Production of variation

The reproductive process, meiosis and fertilization, provide the method by which new combinations of both old and new traits may be “tried out” as new varieties within a species.

Mutation

-An important process in providing

2. Natural Selection

-Individuals that survive are “selected” and are assumed to be those best adapted to survive

-Survivors tend to pass on the genes associated with their adaptive advantages.

3. Speciation

-When enough unique adaptations have been accumulated, in a species’ population,

4. Reproductive Isolation

-If two populations of species are

geographically separated from each other for a sufficiently long period, they may change so greatly that even if geographic barriers are removed the two species will not be able

[pic]

or, another example… the “Founder Effect”

[pic]

[pic]

[pic]

[pic]

5. Time Frame for Evolution

a. Gradualism – Assumes that evolutionary change

-Supported by fossil records

-Gradual change of

b. Punctuated Equilibrium – Assumes that species experienced long geographic periods

• -This stability is “punctuated” by brief periods (a few thousand years) in which dramatic changes occur within a species.

-Punctuated equilibrium is supported by fossil evidence in which little change is noted between most sedimentary layers but

[pic]

-----------------------

includes

Evidence of Evolution

Common ancestral species

Similar genes

which is composed of

which indicates

which implies

which implies

The fossil record

Geographic distribution of living species

Water carries small rock particles to lakes and seas.

Dead organisms are buried by layers of sediment, which forms new rock.

The preserved remains may later be discovered and studied.

Sea level

Sedimentary rocks form in horizontal layers.

When part of Earth’s crust is compressed, a bend in a rock forms, tilting the rock layers.

As the surface erodes due to water, wind, waves, or glaciers, the older rock surface is exposed.

New sediment is then deposited above the exposed older rock surface.

Sea level

Pinta Island

Intermediate shell

Pinta

Isabela Island

Dome-shaped shell

Hood Island

Saddle-backed shell

Hood

Floreana

Santa Fe

Santa Cruz

James

Marchena

Fernandina

Isabela

Tower

Sample of

Original Population

Founding Population A

Founding Population B

Descendants

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download