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Natural Selection
Which mouse is
the fittest? Why?
Fur color
Brown
Tan
Black
White
6 months
8 months
4 months
2 months
# of pups
6
12
2
0
Running
speed
8 m/ min
6 m/ min
9 m/ min
7 m/ min
Bit 5 birds that
tried to attack
her pups.
Chases off 2
snakes that
wanted to eat
her pups.
Relocated her
pups after her
den was
flooded during
high tide.
Had the
deepest and
most well
hidden den on
the beach.
Age at death
Other
Adaptation is a
change in structure or
habits to improve it’s
chances of survival.
The organisms best suited to
their environment have more
chance of survival if the
species falls upon hard
times.
This idea is known as
survival of the
fittest.
Natural selection
is the process by
which these “fit”
individuals survive
& reproduce to
pass on the
advantageous
traits to their
offspring.
This provides a mechanism
for an entire population to
adapt to the environment
& thus will ensure survival.
Charles
Darwin was a
biologist who
studied
animals of the
Galapagos
Islands in
1835.
• Darwin studied finches and
how their ·beak adaptations
allowed them to adapt to take
advantage of food sources in
different ecological niches
(job).
His studies led him to come up
with a theory based on the
process of natural selection.
Charles
Darwin’s
Theory of
Natural
Selection:
Organisms produce
more offspring than
can survive.
There are variations
among the offspring of an
organism caused by
genetic differences.
There is competition
among offspring for
food, space & other
resources.
Individuals with certain
traits are better suited
to survive in their
environment than those
without the traits
Organisms that survive &
reproduce pass the genes
for their useful traits to
the next generation.
Adaptations can only
happen if there is
variety within the
offspring of a
species.
This variety is caused
by genetic variation,
the normal differences
that exist among
individuals of the same
species.
Greater variation can be
caused by mutations which
are caused by random
changes in genes.
Mutations can be
helpful or harmful.
Selective breeding is the
process of breeding
plants and animals for
particular genetic traits.
Selective breeding is most
often seen with domestic
animals like cats and dogs
which are bred for specific
traits such as size, health,
looks, fur type, or their
specialized job.
Selective breeding is also
common in organisms used
for consumption such as
cattle, chickens, pigs,
fruits and vegetables.
Traits that are desirable
in these organisms include
growth rate, survival rate,
disease resistance, and
meat/ egg/ flesh quality.