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

LamarkTheory 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

Iguana

Giant Land Tortoise

• 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 newly-darkened 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