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