Transcript Natural Selection

Natural Selection
“Survival of the Fittest”
Charles Darwin
• Fresh out of college young Charles
Darwin started a 5 year voyage on the
HMS Beagle which became the
foundation for his theory of Natural
Selection.
• In 1859, Darwin proposed a
theory to explain how
organisms changed over
time. He based his theory
on his observation of
plants and animals that he
studied all over the world.
• The HMS Beagle traveled
all over the world and
Darwin collected thousands
of plant and animal samples
and kept detailed notes of
his observations.
• His most important work was during his
visit on the Galapagos Islands.
Natural Selection
• The process by
which organisms
with favorable
traits survive
and reproduce
at a higher rate
than organisms
without the
trait.
Natural Selection Examples
• Would the large tree
finch and the large
ground finch compete
for the same resource?
They would not
compete for the same
resource because one
goes for plant food
while the other goes
for animal food.
Four Parts of Natural Selection
1) Overproduction: Each species produce more
offspring that will survive to maturity
2) Genetic Variation: Individuals in a population are
slightly different from each other with slightly
different traits. Some traits increase the chances of
the individual to survive and reproduce
3) Struggle for Survival: Environment does not have
enough food, water and other resources to support
every individual. Some are killed by other organisms
4) Successful Reproduction: Individuals that are able
to adapt to their environment reproduce offspring
that will have the traits to also be able to adapt.
HUMAN IMPACT
-Genetic Resistance
in Insects
• How can natural
selection be seen
in a population of
insects on a
farm?
The pesticide kills off the weaker insects, leaving the
stronger ones with a resistance to the chemical.
They reproduce and then the pesticide is not as
effective in killing the insects next time.
-Selective Breeding
• In selective breeding humans select
desired traits in animals to be passed
from 1 generation to another.
• Ex: corn or breeding dogs
Speciation
Allopatric speciation due to geographic separation of the Grand Canyon.
Harris's antelope squirrel (Ammospermophilus harrisi) inhabits the canyon's south rim (left). Just a few miles
away on the north rim (right) lives the closely related white-tailed antelope squirrel (Ammospermophilus
leucurus).
Another example is the Tassel-eared Squirrel, where Abert's Squirrel (Sciurus aberti) lives on the south rim and
the Kaibab Squirrel (Sciurus aberti kaibabensis) lives on the north rim.