Download Evidence of Evolution Notes

Evolution
 the process of change within a
population that occurs over a series of
generations
 an attempt to explain why organisms
that are so similar in their molecular
make-up can be so different in form
and function
 Example: all plants have similar cells.
Evidence of Evolution:
Adaptations
 Adaptation: any variation that aids an organism’s
chance of survival in it’s environment
 3 types of adaptations:
1. Structural – parts of an organism that help it to
survive in its environment; external features
ex.
large ears for cooling (desert foxes)
large teeth (beavers)
2. Physiological – body chemistry or metabolism
that help it survive in its environment; internal
features
ex. Bacterial resistance to antibiotics
Bad-tasting chemicals (ladybugs)
3. Behavioral – how an organism acts that helps it
survive in its environment
ex. Hibernation (bears)
Mating behaviors (birds of paradise)
Bird of Paradise
Evidence of Evolution
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Fossils
Embryology
Homologous Structures
Analagous Structures
Vestigial Structures
Physiological Evidence
Biochemical Evidence
1. Fossils (Paleontology)
 Provides direct evidence for evolution
 Gives rise to theory of divergent
evolution, whereby organisms evolve
into a variety of specialized life forms to
ensure a group’s survival. Eventually
each of these life forms may become a
distinct species.
Ancient Fly in Amber Earring
Phylogenetic Trees
 Used to explain the common structures
found among species.
Determining the Age of Fossils
1. Relative Dating -fossils nearer to the surface
are younger
2. Radiometric Dating
-radioactive isotopes: are present in rock in which fossils
may be encased
are unstable, and decay into new isotopes
the length of time of their decay can be measured
by comparing the amount of radioactive isotope to the
amount of the new isotope, based on the half-life
Radiometric Dating
Example:
Potassium-40 decays to Argon-40.
Potassium-40 decays to half its original amount
in 1.3 billion years.
If there are equal amounts of Potassium-40 and
Argon-40 in a rock sample, how old is the
rock sample?
Answer: 1.3 billion years.
Dinosaur Eggs in Chinese
Rock Shop
Petrified Wood - California
2. Embryology
 Embryo’s of different species look similar
(1880’s)… due to a common ancestor?
 Every organism repeats its evolutionary
development (phylogeny) in the stages of
embryo development (ontogeny)
Fish
Chick
Pig
Human
3. Homologous Structures
 structures in different creatures (often
with different functions) have the same
organization
 Gives evidence for divergence, in which
a single structure can change to meet
an organisms needs in a new
environment.
 Example: Bat wing, mole arm, wolf leg
4. Analagous Structures
 have the same function, but different
orgins
 environment can affect the structure of
an organism
 Example: butterfly and bird wing.
5. Vestigial Structures
 structures that no longer serve a useful
purpose
 usually greatly reduced in size
 some structures that were once
considered vestigial are now known to
be necessary for the organism
 Example: dew claws on dogs, pigs and
horses / hips on snakes and whales.
 Shallow Hal
Ambulocetus
Basilosaurus with well developed hind limbs, though reduced in size.
Sperm whales retain hind limb atavisms.
6. Physiological Evidence
 evidence shows that wastes excreted
from birds and reptiles have the same
biochemical make-up
 hormones (I.e. Insulin) from cows and
pigs can be injected into humans
7. Biochemical Evidence
 DNA comparisons show a great deal of
similiarity
 humans and chimps share 96% of their DNA.
 the number of genetic differences between
humans and chimps is approximately 60
times less than that seen between human
and mouse and about 10 times less than
between the mouse and rat
 the number of genetic differences between a
human and a chimp is about 10 times more
than between any two humans