Evolution Theories

•Lamarack vs Darwin

Jean- Baptist Lamarck (1744-1829)

Acquired traits- traits that a organism obtains during its life are passed to offspring (ex: long neck of giraffe)

1.Tendency towards perfection (change because you want to)

2.Use and disuse (structures change if used, disappear if not used)

3.Inherit acquired traits(changes in lifetime passed on to kids)

Lamarck: How did the fiddler crab get a large claw?

Lamarck:

1. Crab has a small claw• feels a larger claw would be more

“perfect” (predators, mates)2. Crab uses claw• makes it larger• acquires a new trait in his lifetime3. Crab has babies• all offspring have large claws

Lamarck:

Charles Darwin(1809-1882)

Natural Selection: Variations among individuals increases survival and are selected based on environment–Adaptations increase fitness

• N

DARWIN∞NATURAL SELECTIONHis theory was influenced by:1. 5-year Voyage on the Beagle

DARWIN2. Galapagos Islands

DARWIN

3. Charles Lyell’s geology book--earth is millions of years old andis constantly changingEX: ocean fossils on mountain tops

DARWIN4.Artificial Selection-pigeon breeds-dog breeds

DARWIN5. Thomas Malthus’ essay on

human overpopulation--too many humans = not enough resources--”weak” will die --“strong” will survive

On the Origin of Species

• Darwin’s book published in 1859• Proposes Natural Selection as the way species form• Controversial……religion

DARWINHow crabs got big claws

1.Some crabs have slightly bigger claws, others have slightly smaller claws (from mutations)

2.The bigger the claw, the more food crabs get

DARWIN3. Big-claw crabs have lots of big-claw

offspring4. Small-claw crabs have few or no

offspring5. Over time, small-claw crabs

become extinct, since big-claw crabs get more food and mates….and therefore more offspring

DARWIN∞NATURAL SELECTION:4 parts1. Natural Variation--individuals in a population vary

DARWIN∞NATURAL SELECTION:4 partsCompare your hand size to your

table partners….this is natural variation

DARWIN

Because of this variety:∞ some are very well-adapted

(w.a.) to their environments (fast, strong, camouflage..)

DARWIN

Because of this variety:∞ --others are not w.a.

DARWINNATURAL SELECTION:4 parts2. Inheritance

--parents pass traits to kids--through genes--kids look like parents

NATURAL SELECTION:4 parts3. Overproduction of offspring-too many offspring are produced—

there is competition

NATURAL SELECTION:4 parts4. Reproductive Advantage-traits that increase reproductive

success will be more common in the next generation

4. Reproductive Advantage-w.a. survive better than not w.a.-w.a. have more w.a. offspring -not w.a. have few or no offspring--“survival of the fittest”

4. Reproductive AdvantageOver time, this results in changes in

the characteristics of a species∞-w.a. species form∞-not w.a. species disappear

DARWIN”descent with modification”

DARWIN

DARWIN