Transcript File

WHO WAS CHARLES
DARWIN AND WHAT
DID HE REALLY SAY?
Charles Darwin was
one of the most
important biologist of
the 1800’s and one of
the most important
biologist of all time.
He proposed the
theory of evolution by
natural selection.
Charles Darwin
was born in
England in 1828.
This was the
Victorian Era
when England
was exploring the
world bringing
back scientific
knowledge from
the farthest
reaches of the
Earth.
He studied medicine and the ministry
.
He met John
Henslow, a
professor of
botany, who
took him out
on collecting
trips in
Scotland.
These trips
sparked his
serious interest
in science.
Henslow introduced
Darwin to the renown
geologist Adam Sedgwick.
On field trips with
Sedgwick Darwin learned
about modern geology.
Through the
influence of
these men and
his father,
Darwin
accepted a
position as
naturalist
aboard the
H.M.S. Beagle.
The Beagle was commissioned for a five year
voyage around the southern hemisphere
Darwin’s
observations
included the
discovery of
fossil
mammals
different
from
anything
living today.
One of the
Beagle’s
stops was
the
Galapagos
Islands off
the coast
of
Ecuador.
While studying the organisms on the island,
he made some amazing observations.
Although the
iguanas on the
Galapagos
were similar to
the iguanas in
South
America,
there were
also many
differences.
He observed that
the giant
tortoises were
different on each
of the islands
and theorized it
was due to their
environment
He noticed
finches that
were closely
related, but had
different bill
structures
depending on
their habitat.
Later,Darwin began
to think deeply about
the observations he
had made during the
voyage. He consulted
other scientists and
conducted
experiments to
support his ideas.
Darwin
published a
book he had
written about
his ideas
titled “Origin
of Species”.
(1853)
Darwin began
the book by
discussing how
humans have
“selectively
bred” the wild
rock pigeon into
different
varieties.
Darwin gives
many examples of
selective breeding
such as broccoli,
brussel sprouts,
and cauliflower,
which have all
been selectively
bred from wild
cabbage.
By selecting
certain
plants for
breeding
humans
have
created
many
varieties,
such as seen
in roses.
In only a few thousand years,
selective breeding has produced the
vast varieties of dogs we have today.
The ancestor of all these different
breeds is the wolf.
Darwin
hypothesized
that the same
thing happened
in nature but
over hundreds
of thousands of
years, such as
the evolution of
the horse.
Over time, mutations to the horse’s foot decreased
the number of toes thus increasing speed. Since
this adaptation was an advantage, the faster
horse reproduced and past the trait down to its
offspring
Natural selection takes place when
variations give the organism, such as
the checkered moth, a reproductive
advantage.
Different
variations are
better suited for
different
environments,
such as in
members of the
dog family.
If the new variation increases the ability
of an organism to reproduce, then more
genes are passed to the next generation
Just like with selective breeding, favorable
variations are passed to the next generation
resulting in new breeds.
During the
billions of
years of life on
earth, little
variations add
up to big
differences.
• Natural selection is the
process by which individuals
whose genes are better
adapted to the environment
are more likely to survive
and reproduce than other
members of the species
Natural selection is the accepted
scientific explanation for the evolution of
life on earth.
Several Factors affect
Natural Selection
• Over production
• Competition
• Variations
• Selection
• Overproduction
Most species
produce more
offspring than
can possibly
survive.
• Competition:
Offspring
compete with
others for limited
food and other
resources. Only a
few will survive
long enough to
reproduce.
• Variations: Differences between
members of a species, which are
controlled by genes.
• Selection: Variations make
some individuals better suited
to the environment and,
therefore, more likely to survive
and reproduce. Helpful
variations accumulate and
unfavorable ones disappear
We see natural selection taking place today because
of the chemicals we are adding to the environment.
When a pesticide is first applied, only a few insects survive.
These survivors reproduce and on the next application
many of the ofsprings of the original survivor survive.
Eventually, all the insects are offsprings of the
original survivors and the pesticide has no effect on
the entire population.
For Natural selection to take
place the organism not only
has to be better adapted to the
environment, but also has to
reproduce, thus passing the
trait on to its offspring.
Over a period of time
natural selection can
lead to evolution.