Download MaryPaulEvidence Evolution

Evidence for Evolution
“There is grandeur in this view of life, with its several powers,
having been originally breathed by the Creator into a few forms or
into one; and that, whilst this planet has gone cycling on according
to the fixed law of gravity, from so simple a beginning endless
forms most beautiful and most wonderful have been, and are being
evolved."
-Charles Darwin, Origin of Species (1859)
I.
What is Evolution?

The process by which modern organisms have descended
from ancient organisms
II. Evolution: Fact or Theory?
A. Define Fact: Has undergone repeated tests over a period of
time. More certain than a theory.
B. Define Theory: Not yet “proven”. A collection of carefully
reasoned and tested hypotheses, supported by evidence.
C.
Examples - Fact or Theory?
1.
Gravity exists.
•
There is no doubt that gravity does exist. What goes
up, must come down, right?
•
However, physicists do not completely understand
how gravity works!
Sir Isaac Newton
2.
Charles Darwin
Life on Earth has changed over time.
•
There is no doubt that life on Earth does change over
time.
•
However, explaining how life changes over time
continues to be one of the great challenges of biology.
III. Evidence for Evolution
A.
Similarities in Early Development
1.
Embryos of many different animals are similar in
appearance, especially during the early stages of
development.

The similarities of vertebrate embryos show that
similar genes are at work
Bio pg. 641
B. Similarities in Body Structures
1.
Homologous Structures - parts of different
organisms that developed from the same ancestral
body part

Bio pg. 284
Examples: The limbs of various vertebrates are
similar in structure
2. Vestigial Organs - Organs that are so reduced in size or
function that they are merely traces of similar organs in
other species
Examples:

•
tail bone and appendix in humans
•
tiny bones on the underside of pythons and boa
constrictors
•
Whale limbs
Bio pg. 285
C. Similarities in Chemical Compounds
1.
Genetic Material: All organisms, from bacteria to
humans, use DNA and /or RNA to carry information
from one generation to the next

DNA
Example: DNA of all eukaryotic organisms has the
same structure and replicates in the same way
RNA
D. The Fossil Record
1.
Species have gone extinct

2.
New species have developed

3.
Example: Dinosaurs
Example: Homo sapiens
Species have changed over time
E. Transition Fossils
1.
Tiktaalik

2.
Example: Fish to Amphibian
Archaeopteryx

Example: Dinosaurs to Birds
3.
Ardipithecus ramidus
4.
Australopithecus afarensis (Lucy)
5.
Homo erectus
F.
Observed Evolution
1.
Examples:
1.
Drug resistance in bacterial
strains

Insecticide resistance

England’s Peppered Moth
Bio pg. 297
IV. How Does Evolution Occur?
A.
Early Theories
1.
Jean Baptiste de Lamarck (1744-1829) was one of the
first scientists to recognize that living things change
over time
a. Early Theories used by Lamarck
 A Desire To Change - Organisms change because of
an inborn urge to better themselves. (ex. Birds really
wanted to fly!)
 Use and Disuse - Organisms could alter their shape
by using their bodies in new ways (ex. Organs would
increase in size if they were used a lot and vice versa)
 Passing on Acquired Traits - Acquired
characteristics are passed on to future generations
IV. How Does Evolution Occur?
B. Early Theories
1.
Geologist James Hutton (1726-1797)—the cumulative
effect of slow but continuous geologic processes can
lead to profound change
2.
Geologist Charles Lyell (1797-1875)– that past geologic
processes continue to operate and at the same rate
3.
French scientist Georges Cuvier (1769-1832)—studying
fossils: the deeper (older), the more different from
current life
2. Charles Darwin and The Beagle
a.
Christmas 1831, a young Englishman named Charles Darwin
set sail on the Beagle for a 5 year cruise around the world
b.
Darwin’s keen observations, data collection and analysis
remain the foundation for evolutionary theory today
B.
Darwin’s Theory of Natural SelectionThe process by which the organisms whose characteristics are
well-suited for their environment survive and reproduce.
1.
The Three Steps of Natural Selection
(1) Variation:

Gene mutations and recombinations provide the
variation upon which natural selection acts
(2) Selection:

In the struggle for existence, organisms either
survive and reproduce or do not.

Far more organisms are born than ever grow to
adulthood

Those organisms with adaptations well-suited for
the environment are “selected” to survive
(3)
Reproduction:
 Best-fit organisms have the highest probability of
successfully reproducing
 Favorable characteristics (adaptations) will be passed on to
the offspring
 Organisms in future generations will become better and
better adapted to their environment
2.
Evolutionary Fitness
 In summary, each time an organism reproduces it passes
copies of its genes to its offspring.
 Evolutionary Fitness: the success an organism has in
passing on its genes to the next generation.
Note: Evolution occurs only if genes (and traits) are passed
on and measured in future generations!