Download NATURAL SELECTION:4 parts

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 lifetime
3. Crab has babies
• all offspring have large claws
Lamarck:
Charles Darwin
(1809-1882)
• N
Natural Selection: Variations among
individuals increases survival and are
selected based on environment
–Adaptations increase fitness
DARWIN
∞NATURAL SELECTION
His theory was influenced by:
1. 5-year Voyage on the Beagle
DARWIN
2. Galapagos Islands
DARWIN
3. Charles Lyell’s geology book
--earth is millions of years old and
is constantly changing
EX: ocean fossils on
mountain tops
DARWIN
4.Artificial Selection
-pigeon breeds
-dog breeds
DARWIN
5. 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
DARWIN
How 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
DARWIN
3. Big-claw crabs have lots of big-claw
offspring
4. Small-claw crabs have few or no
offspring
5. Over time, small-claw crabs
become extinct, since big-claw
crabs get more food and
mates….and therefore more
offspring
DARWIN
∞NATURAL SELECTION:4 parts
1. Natural Variation
--individuals in a population vary
DARWIN
∞NATURAL SELECTION:4 parts
Compare 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.
DARWIN
NATURAL SELECTION:4 parts
2. Inheritance
--parents pass traits to kids
--through genes
--kids look like
parents
NATURAL SELECTION:4 parts
3. Overproduction of offspring
-too many offspring are produced—
there is competition
NATURAL SELECTION:4 parts
4. 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 Advantage
Over 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