Natural
Selection
A species is a group of
organisms with similar
characteristics whose members
are able to reproduce and make
fertile offspring.
Charles Darwin was a British
naturalist who developed the
theory of evolution in the mid1800’s.
He developed his theories while
studying hundreds of species
as he sailed around the world
on the HMS Beagle in the
1830’s.
He was especially interested in
the variation
among animals
in the Galapagos
Islands.
He published his
theories on
evolution by
natural selection
in 1859 in a
book called
On the Origin of Species.
Natural selection is the process
by which organisms that are
best adapted to their
environments are the ones most
likely to survive and reproduce.
It is sometimes called “Survival
of the Fittest.”
The concept of natural
selection is actually quite
simple, and its 4 principles
are all common sense.
http://franklinscience.weebly.com/natural-selection.html
1. Variation exists within a
population. Not all individuals
within a species are exactly
alike. Sexual reproduction and
random mutations
create variation in
a population.
2. Among this population,
there is competition for
resources.
Organisms can produce more
offspring than their
environment can support. If
there are plenty of resources
(food, water, mates), then the
population will keep growing
until its carrying capacity
has been reached.
Carrying capacity is the
maximum number of
organisms an area can
support.
When this limit
is reached,
individuals
must compete against one
another for food, water,
mates, etc.
3. Survival of the “Fittest."
This is survival by those
organisms that are
best adapted to their
environment.
Note that "fittest" does
not necessarily mean
strongest or fastest or
smartest. It refers to
those that are best
adapted.
An organism that is well
adapted is more likely to
survive and reproduce,
passing on its successful
traits to the next
generation.
4. Genetic Inheritance. Genes
are passed from parents to
offspring.
Parents with
successful
genes that
provide a
survival advantage, pass those
genes on to their offspring.
These parents are also likely
to have more offspring than
other, less "fit" individuals.
Humans can change an
organism’s traits by selecting
which organisms will reproduce.
Selective breeding is the
deliberate breeding of plants or
animals for desired traits. It is
also called artificial selection.
Much of the food we eat is a
result of selective breeding.
For example, cows may be bred
for milk production, and
chickens may
be bred for egg
production.
Most pets are also a result of
selective breeding.
Domestic cats were bred from
wild cats, and dogs were bred
from wolves.
Link to Natural Selection
video:
https://www.youtube.com/watch?v=JiSuK_Dvdtg