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Unit 7
EVOLUTION
Ideas About Evolution
• I. Ideas About Evolution
• A. Evolution- change in inherited
characteristics of a species over time.
– 1. A species is a group of organisms that
share similar characteristics and can
reproduce among themselves
B. Early Models of Evolution
• 1. Theory of Acquired
Characteristics
– Jean Baptiste de LaMarck
proposed hypothesis
suggesting that traits
acquired by the parents
during their lifetime were
inherited by their offspring
– Ex.- if parents were
muscular, the children would
be too
– Evidence does not support
this theory
Lamark
Theory of acquired characteristics
•
Lamark said
organisms acquired
traits by using their
bodies in new ways
•
These new
characteristics were
passed to offspring
•
Lamark was totally
wrong!
2. Darwin’s Model of Evolution
• A. In 1831 Charles Darwin set sail on the
HMS Beagle to explore the South
American coast.
– 1. He recorded observations of the different
plant and animal species he saw.
– 2. amazed by the variety of life he saw on the
Galapagos Islands he hypothesized they must
have come from Central and South America.
He also saw forms of life never seen
anywhere else
Giant Cactus Tree
Giant Land Tortoise
Iguana
• 3. He also observed 13 different species of
finches.
– a. they were similar except for body size,
beak shape, and eating habits
– b. they looked a lot like finches he had seen in
South America
– c. he hypothesized they must have all evolved
from that S American species. Those that had
the traits necessary to survive did and those
that didn’t died out.
4. Darwin’s Theory of Natural
Selection
• A. Natural selection means that those best
suited to their environment are more likely
to survive and reproduce (survival of the
fittest)
• B. theory remains one of the most
important ideas in life science study today
5. Principles of Natural Selection
1. Organisms differ; variation is inherited
2. Organisms produce more offspring than
survive
3. Organisms compete for resources
4. Organisms with advantages survive to pass
those advantages to their children
5. Species alive today are descended with
modifications from common ancestors
B. Variations and Adaptation
• 1. Variation- appearance of inherited trait
that makes an individual different from
other members of same species.
• a. Can be small (# of petals on a flower) or
large (albino animal)
• b. New species can evolve from variations
if enough of the variation spreads
throughout a population
• 2. adaptation- helpful variation that makes
an organism better suited to their
environment
• 3. mutation- source of variation caused by
a change in the DNA
• 4. The isolation of some individuals from
others by geography or climate can also
result in evolutionary change
CONCEALING COLORATION
• USING COLORATION TO HIDE
AGAINST A BACKGROUND OF THE
SAME COLOR
• MANY ANIMALS IN THE ARCTIC HAVE
WHITE COLORING TO BLEND IN WITH
THE SNOW THAT SURROUNDS THEM.
DISRUPTIVE COLORATION
• BREAKS UP THE SOLID OUTLINE OF
AN ANIMAL WITH SPOTS, STRIPES, OR
OTHER PATTERNS SO THAT THE
ANIMALS DOESN’T STICK OUT
AGAINST THE BACKGROUND. A
SUMATRAN TIGER HAS STRIPES THAT
HELP IT HIDE AMONG THE TALL
GRASSES
DISGUISES
• WHEN ANIMALS OR PARTS OF THEIR
BODIES RESEMBLE OBJECTS IN THEIR
ENVIRONMENT. THE INSECT CALLED
THE WALKING STICK LOOKS LIKE A
SMALL TREE BRANCH OR TWIG
COUNTER SHADING
• WHEN THE COLORATION OF THE UPPER
PARTS OF AN ANIMAL IS DARKER THAN ITS
UNDERSIDES. THIS CAUSES THE EFFECT
OF SUNLIGHT TO BE COUNTERACTED.
MOST WHALES ARE COUNTER SHADED. IF
YOU LOOK UP AT A WHALE YOU WOULD
SEE A LIGHT COLOR, JUST AS IF THE
WHALE WAS NOT THERE- BLENDS IN WITH
THE SKY. IF YOU LOOK DOWN ON A WHALE
YOU SEE DARKNESS LIKE THE OCEAN
FLOOR.
MIMICRY
• AN ANIMAL COPIES, OR MIMICS, A
COLOR OR FORM OF SOMETHING
ELSE. MANY BUTTERFLIES USE
MIMICRY TO SURVIVE. HAIRSTREAK
BUTTERFLIES HAVE FALSE ANTENNAE
AND SPOTS ON THE BACK OF THEIR
WINGS. BIRDS PECK AT THE WRONG
END TRYING TO GRAB THE HEAD, AND
THE BUTTERFLY CAN GET AWAY.
•
The
Peppered
Moth
The light-colored form of the moth, known as typica, was
the predominant form in England prior to the beginning
of the industrial revolution. the typica moth's speckled
wings are easy to spot against a dark background, but
would be difficult to pick out against the light-colored
bark of many trees common in England.
Around the middle of the 19th century, however, a new
form of the moth began to appear. The first report of a
dark-colored peppered moth was made in 1848. By
1895, the frequency in Manchester had reached a
reported level of 98% of the moths. This dark-colored
form is known as carbonaria, and it is easiest to see
against a light background. As you can well imagine,
carbonaria would be almost invisible against a dark
background, just as typica would be difficult to see
against a light background. The increase in carbonaria
moths was so dramatic that many naturalists made the
immediate suggestion that it had to be the result of the
effects of industrial activity on the local landscape.
coal burned during the early decades of the industrial revolution
produced soot that blanketed the countryside of the industrial
areas of England between London and Manchester. Several
naturalists noted that the typica form was more common in the
countryside, while the carbonaria moth prevailed in the sooty
regions. Not surprisingly, many jumped to the conclusion that the
darker moths had some sort of survival advantage in the newlydarkened landscape.
In recent years, the burning of cleaner fuels and the advent of
Clean Air laws has changed the countryside even in industrial
areas, and the sootiness that prevailed during the 19th century
is all but gone from urban England. Coincidentally, the
prevalance of the carbonaria form has declined dramatically. In
fact, some biologists suggest that the dark forms will be all but
extinct within a few decades.
The "typica" form of
the moth
The "carbonaria"
form
D. The Speed of Evolution
• 1. Gradualism
– a. slow, steady,
and continuous
evolution
– b. there is a
record of all the
intermediate
forms of the
species
• 2. Punctuated Equilibrium
a. shows rapid evolution of a species
occurring by a mutation of a few genes,
producing large changes in body form over
a short period of time.
b. used to explain the gap in the fossil
record.
c. bacteria have evolved this way over
the course of a few decades to become
antibiotic resistant
Evidence of Evolution
• 1. Fossils
– Types of fossils
• Imprint (leaf, feather, etc leave imprint on rock that
hardens)
• Mineralized (petrified wood- minerals replace wood
of bone)
• Frozen fossils
• Fossils in amber (sticky resin from cone bearing
plants hardens and traps insects)
• Cast fossils ( minerals fill in animal tracks, shells,
etc)
Evidence for Evolution
• 2. Embryology
• Incredible similarities
in embryos of
different species
provides evidence of
common ancestor
– Patterns of embryo
development are also
important.
Evidence of Evolution
• 3. homologous
structures- body
parts that are
similar in
structure and
origin; can also
be similar in
function.
Evidence for Evolution
• 4. Vestigial Structures- structures that no
longer seem to have a function in an
organism.
• 5. DNA- similar DNA can suggest common
ancestry