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.
To fulfill the demand for quickly locating and searching documents.
It is intelligent file search solution for home and business.
Related searches
- evolution of plastic surgery
- evolution of surgery
- dr lipo evolution md
- the evolution of surgery
- evolution md plastic surgery
- evolution and medicine
- evolution of education in america
- evolution of special education
- evolution of education timeline
- evolution of education
- evolution of education paper
- usa payroll evolution payroll