Transcript 37. Evolution Notes

Evolution
Charles Darwin
• 1700’s- Natural Theology dominated the
time which said adaptations of organisms
was evidence that the “creator” had
designed every species (specifically
created) for a particular purpose for a
particular environment.
• *BIG DIFFERENCE BETWEEN
EVOLUTION VS. CREATIONISM
• -Idea that all species were created at
same time says they would all appear
in rocks of same age but this in
contrast to what paleontologists
observe because some species appear
than disappear in different rock layers.
• Jean Baptiste Lamarck- (1744-1829)
• -published theory of evolution in 1809
(year Darwin was born)
• -was in charge of invertebrate collection
at Natural History Museum in Paris
• -saw many ladders of life that species
could move up (toward greater complexity)
• -Evolution-according to Lamark was
toward greater complexity
• Lamarck’s Mechanism for Evolution
• 1. Use/Disuse
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Parts used= larger/stronger
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Parts not used= deteriorate (waste away)
• 2. Acquired Characteristics- modifications
acquired during lifetime can be passed to
offspring (ex. Long giraffe neck)
•
-NO EVIDENCE YET THAT GENES ARE
CHANGED BY THIS
Lamarck’s theory of acquired
characteristics
• Charles Darwin-(1809-1882) born in
Shrewsbury, England
• -read nature books- liked to fish, hunt, & collect
insects as a boy
• -Charles earned his B.A. in 1831 & went w/
Captain Robert Fitzroy to sail on HMS Beagle
• -goal of the voyage  chart poorly known
stretches of the South American coastline
Voyage of HMS Beagle
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-Darwin
spent most of his time collecting
diverse/exotic species
-Darwin noticed plants/animals had different
characteristics than those in Europe
*PUZZLING- Galapagos Islands- 900 Km
west of South America but he saw animal
species on Gal. that weren’t found in other
parts of the world
ex. Finches- 13 types collected; very similar
but differed most in beaks  adapted for
special diet
-large ground finch- large beak for cracking
seeds
-small tree finch- beak used to grasp insects
Darwin’s finches
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Darwin’s Findings
Origin of new species
Closely
related
Adaptation to environment
*Finch results- Darwin believed that if 1
species is separated by a geological
barrier they could become dissimilar to be
called different species
• Darwin’s evidence for evolution
• 1. Biogeography- islands  species of
plants/animals that are native to island but
are closely related to mainland species
• 2. Fossils- Bacteria  prokaryotes are earliest
known fossils so they should precede all
eukaryotes
• *Fossils do show this order (prokaryotes 
eukaryotes)
• ex. Vertebrate record
•
fossil fishes  amphibians  reptiles
mammals birds
• Darwin believed all organisms are related through
“common ancestory”
• Darwin’s Beliefs about Evolution
• 1. Struggle to Survive
• 2. Individuals who inherit characteristics
that best fit the env. will leave more
offspring than less-fit individuals
• Evolution- change in populations over time
• Charles Darwin- (1809-1882)
• -published On the Origin of Species (1859)
which had 2 points:
• All species evolve from ancestors
• Mechanism for evolution  natural
selection
• Evolution according to Darwin
• *Natural Selection- mechanism for change in
populations
• 1. Organisms produce more offspring than can
survive
ex. Fish lay millions of eggs
• 2. In any population, individuals have variations
ex. Fish differ in size, shape, color,
speed, etc.
Evolution according to Darwin
• 3. Individuals with certain useful variations such
as speed are more likely to survive in their
env. passing those variations on to the next
generation
• 4. Overtime, offspring w/ certain variations
(adaptations) make up most of the population,
& may look entirely different from their
ancestors
• *Modern Biologists-define evolution as a “change in a gene
pool (gene frequency) of a population over time”
• SO, THE SMALLEST UNIT THAT CAN EVOLVE IS A
POPULATION!!
Natural Selection
This diagram shows the natural selection process for a
population with dark coloration.
• Adaptations/Structures which give
evidence for evolution
• 1. Mimicry-structural adaptation that
enables one species to resemble another
species
• ex. Yellow jacket vs.
syrphid fly
•
(harmful)
(harmless-looks like yellow jacket)
• So, predators avoid eating both insects
• 2. Camouflage- adaptation that enables
species to blend w/ their surroundings
•
-survive to reproduce b/c can’t be
found by predators
Flounder blending in
with sea floor rocks
• 3. Homologous Structures- can be
similar in arrangement, in function, or both
•
-evidence that organisms evolved
from a common ancestor
• ex. Whale, crocodile, & bird forelimbs
are similar
Homologous Structures
• 4. Analogous Structures- body parts of
organisms that do not have a common
ancestor but are similar in function
•
ex. Wings of butterfly & wings of birds
• . Vestigial Structures- body structure
that has no function in a present day
organism but was probably useful to an
ancestor
• ex. Ostrich- has reduced forelimbs & can’t
fly (ancestors probably foraged for food on
land & nested on ground so they got too
large to fly
Vestigial Structures
• Embryology- embryo- earliest stage of
growth & development
ex. Embryos of fish, reptiles, birds,
mammals all look the same & suggest a
common ancestor
• Biochemistry- compare/contrast the
DNA/RNA of different species to
determine how similar (related) they are to
each other.