Download Ch. 15 Evolutionary Theory

Wolodkowicz
Biology 1H
Chapter 15 Evidence of Evolution
Evolution: Theory that species change over time, or the change in the genetic make-up of a population over
a period of time. Two ways of observing Evolution: Through Indirect Evidence and Direct Evidence.
I.
Indirect Evidence of Evolution- Evidence for evolution by observing the history of the earth.
A. Fossils- traces of once-living organisms usually found imbedded in rock (sedimentary
rock). (Indirect because we are not seeing a creature change before our eyes but rather
studying the change of creatures through millions of years.) Examples of fossils: hard
parts of an organism such as bones, shells, molds (impression of the organism), casts (cast
forms around dead creature, creature decomposes, cast is left).
1. Dating fossils
a. Rock Sedimentation or the law of superposition- in a rock layer or
stratum, the oldest rocks or fossils are found at the bottom while the
newer rocks or fossils are found toward the top.
b. Radioactive Carbon Dating- Living organisms are made of both C12 and
C14. Carbon 14 is radioactive. Scientists can determine the amount of
C14 in your body to determine your age. This is because C14 has a ½ life
of 5,568 yrs. Thus if ½ of your C14 is gone you have lived 5,568 yrs. C14
can be used to measure fossils up to 50,000 yrs. Old.
2. Fossil Record- worldwide standard developed by scientists that records layers
of sedimentary rock and the fossils they
contain.
3. By observing the fossil record from oldest to most recent, one notes: a change
from all organisms living in a marine environment, to living on land, a change
from simple, one celled organisms, to multicellular organisms, intermediate
organisms (amphibians), and it takes much time for evolution to occur.
B. Evidence from living organisms- to determine if a species has evolved, scientist compare,
common ancestry, structure, embryonic development, vestigial structures, and
biochemistry.
1. Common Ancestry- scientists can show that a group of living species may have
come from a common ancestor.
2. Structures of organisms: 2 types
a. Homologous Structures- Structures that are similar, but have different
functions. Shows that these organisms have the same ancestor. Ex:
Whale’s flipper is similar in structure to a human but the Whale’s
flipper is for swimming.
b. Analogous Structures- structures that have similar function, but differ
in structure (does not necessarily show
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that the organisms come from a similar ancestor): insect wing, no skeleton,
veins support it, bat has an internal skeleton and covered by muscle and
skin.
3. Embryonic Development- Early stages of development very similar in a fish,
human, pig (tail & gills). Ernst Haeckel stated the famous quote in Biology:
“Ontogeny recapitulates phylogeny” which means: embryonic development
repeats evolutionary history
4. Vestigial Organs- an organ or part of an organism that at the present does not
appear to have a function. Ex. Appendix and coccyx. Organisms with
vestigial structures share a common ancestry with organisms in which they
have the same homologous structure.
5. Comparative biochemistry- similar organisms have similar DNA and amino
acid sequences. Ex. Only one amino acid difference in the sequence for
hemoglobin (protein in the blood) in apes and humans.
II.
Direct Evidence of Evolution- Evidence of Evolution that one can visually observe over time.
A. Microevolution- small observable changes in evolution.
1. Changes in genetic make-up- the organism whose genetic make-up will aid in
its survival will reproduce & pass on those traits. Ex. When one takes
Wolodkowicz
Biology 1H
III.
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antibiotics, the antibiotics will kill most of the bacteria, but if just one
bacterium is resistant to the antibiotics (different genetic make-up), it will
survive and reproduce more bacteria resistant to the antibiotic…they have
evolved.
2. Observations in nature- Ex. Peppered moths. Peppered moths lived in
wooded areas of England. Prior to 1848, they were light gray with dark
markings. A few were black. The black were easy pray for birds. After 1898,
Industrial Revolution caused soot to cover trees. The numbers of black moths
increased, the number of gray moths decreased (Industrial Melanism).
Early Evolutionary Theory
A. Jean Baptiste de Lamarck (1744-1829)- Created a theory of evolution based on the
inheritance of acquired characteristics. Ex. He believed that giraffes originally had short
necks. But food was scarce so they reached for leaves in tall trees. In doing this they
stretched their necks. Their offspring then inherited this trait. This is not supported.
Special use of a body part does not change the genetic make-up of that part.
B. Charles Darwin (1809-1882) (Father of Evolution) - Darwin was a naturalist (study living
organisms) and in 1831 was selected to be the naturalist on the voyage of the HMS Beagle,
a British ship chartered for a five-year mapping and collecting expedition to South
America and the South Pacific. One of the places he visited was the Galapagos Islands
(Islands off of South America).
1. Studied 14 different species (definition of a species is that members of a species
can breed and produce fertile offspring (Donkey with a Horse= Mule) FinchesHe observed that the different species all were very similar (homologoussimilar ancestor) except that they had different beak structures based on
environment and diet. Ex: Warbler finch –slender, pointed bill, feeds on small
insects, lives in trees. Medium ground finch- very powerful, heavy bill, good
for crushing, feeds on large seeds and nuts, lives on the ground.
2. Darwin using his discoveries wrote The Origin of Species in which he based his
theory of evolution on Natural selection: Conditions in nature determine
which organisms survive and reproduce. Ex: An antelope born with one leg
shorter then the other 4 cannot run as fast as the other antelopes. He will thus
be more likely to get caught and eaten. Thus, only the strong will survive and
pass on their genes. In terms of giraffes: The giraffes with the longer necks
were able to survive and pass on their genes (could reach the leaves of tall
trees). While the giraffes with short necks starved and did not pass on their
genes. Darwin’s additional ideas based on natural selection:
a. Populations produce more offspring than are likely to survive.
b. Variation- individuals in populations vary and these variations are
inherited.
c. Survival of the fittest- the strongest will survive and the weak will
perish.
d. Organisms within a species are not identical. Some are more likely to
survive then others. These individuals will be better suited to survive
and pass on their traits.