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Transcript
EVIDENCE OF EVOLUTION
Evolutionary Theories
LAMARCK
Developed two theories of evolution:
 Law of Use and Disuse: the more a
part is used, the stronger it becomes

Inheritance of Acquired
Characteristics: theory stating that
useful traits developed during a lifetime
are passed on to offspring
EXAMPLES
EXAMPLES

Children of cyclists
inherit the strong
muscles of their
parents
WEISMAN

Disproved Lamarck’s theory
that acquired traits could be
inherited by cutting off the
tails of mice then mating
them

RESULT: offspring of tailless
mice were always born with
normal length tails
MALTHUS

Believed that human population increased
geometrically (2, 4, 8, 16)

Food production increased arithmetically (1,
2, 3, 4)

RESULT: millions of people must die to keep a
balance between the need/supply of food
DARWIN
Background Information:
 Traveled for five years aboard the HMS
Beagle
 Made significant discoveries by studying
finches on the Galapagos Islands
 RESULT: noticed that species on island
resembled mainland species, but had
adapted to different regions
THEORY OF
NATURAL SELECTION

Nature acts as a selecting agent of an
organism’s traits

Organisms better adapted to the environment
survive and reproduce more successfully than
organisms that are not as well adapted

Overall theme: traits that help an
organism survive in a changing
environment are passed on to offspring
DARWIN’S MAIN IDEAS

Overproduction:
a population
generally produces
more offspring than
can survive in an
environment
COMPETITION

Definition: there
is a struggle
between organisms
for space, food,
water, light,
minerals, and other
limited resources
VARIATION

Definition: members of a population
show differences in traits that make
certain individuals better adapted to
survive

Types of variations—differences in size,
structure, color, etc.
NATURAL SELECTION

Some variations are more helpful than
others—there is a natural selection against
organisms that cannot adapt

Organisms that cannot adapt die
SURVIVAL OF THE FITTEST

Applies to those
individuals that have
variations that
enable them to live
and reproduce
INHERITANCE OF VARIATIONS

Organisms with more
helpful variations are
more likely to survive
and reproduce,
passing on variations
to offspring
EVOLUTION OF NEW SPECIES

Variations
accumulate over
long periods of
time

Eventually, there
are so many
variations, a new
species evolves