Download G1-2 Evolution Ch 15

Evolution Ch 15 G1-2
I.
Darwin
A. General Facts
1. 1831 – 22 yr. old Charles Darwin set sail on 5 yr. voyage on
HMS Beagle
2. Job – a. record plants and animals
b. mapping of S. America and S. Pacific
3. Observations
a. Marine fossils 14,000 ft above sea level
b. land lifted by earthquakes
c. living sloths and bones of much larger sloths
d. 13 similar, but separate species of Galapagos Island
finch (distinctive bills for particular food sources).
e. Many of Galapagos Island’s organisms similar to
mainland with slight differences.
4. Galapagos Island Species
1. Cormorants – fly on mainland/ flightless
on island.
2. Iguana – leaf eating on mainland with sm.
Claws/ sea weed eating with lg. claws on
island.
5. Publication of “Origin of Species”
a. worked with Alfred Wallace (species collector)
b. Hypothesis – natural selection
c. Presented hypothesis in 1858
B. Darwin’s Theories
1. Descent with Modification
a. newer forms in fossil record are modified descendants of older
species.
b. All species descended from one or a few original types of life.
2. Modification by Natural Selection
a. Adaptive Advantage – favorable traits – allow greater
adaptation/ greater likelihood of surviving descendants – pass
on traits.
b. Unfavorable traits – less likelihood of offspring – traits are not
passed on
c. Selection conditions change as the environment changes
d. Rapid changes in environment lead to extinction.
B. Evidence of Evolution
1. Homologous and Analogous Structures
a. Homologous features – similar features that originated in
common ancestor (finches’ beak)
b. Examples – homologous features: penguins, alligator,
bats and humans all have very different arms – all share a
humerus, radius, ulna, carpals, metacarpals, and phalanges.
c. Analogous Structures – Serve identical functions, but have
very different anatomy and embryologic development
*Theory – traits evolved independently – not related
(example: humming birds and bees both hover over
flowers).
2. Vestigial Structures –
a. Serve no useful function (example: humans have a
tailbone and appendix/ some snakes have tiny pelvic bones
and limb bones/ whales have pelvic bones and 4-chambered
stomaches/ sm. Percentage of sperm whale have tiny leg
bones.)
3. Embryology –
a. Many different vertebrates look very similar in early fetal
development (fish, rabbit and gorilla) p291
4. Similarities in Macromolecules –
a. Amino acid sequences of homologous proteins (example:
hemoglobin are similar among different species).
b. The more closely related, the more similar the amino
acid sequence (human and gorilla hemoglobin differ by
one amino acid/ human and frog hemoglobin differ by
67 amino acids).
II Patterns of Evolution
A. Coevolution
1. Predators and their prey often coevolve
2. Plant-eating animals and plants often coevolve
(example: bats feed on nectar, flowers are light in color to see at night)
B. Convergent Evolution – 2 unrelated organisms evolve similar traits
1. Some organisms look similar, but are not related (shark and porpoise).
2. Occurs when environment selects similar phenotypes (streamlined
bodies and similar fins).
C. Divergent Evolution – 2 related organisms become more dissimilar
1. Changes in environment lead to different adaptations.
2. Adaptive Radiation – many species evolve from single ancestral
species (different food sources, climate, etc.).
3. Artificial selection – selective breeding in domestic plants and animals
(much quicker than natural selection).