Transcript Evolution

Evolution
Evolution is the
change of hereditary
features of an
organism over time
In 1809, Jean Baptiste de
Lamarck proposed the
“theory of aquired
characteristics”
This theory said that
organisms evolve by keeping
traits that their parents
developed during their lives.
For example, if your parents
were bodybuilders, then you
would be born with big muscles.
This theory was not
accepted!
In the mid1800’s, an
Englishman
named Charles
Darwin
proposed the
theory of
evolution that
we accept today.
Hello, my name
is Chuck.
In 1859, Darwin
noticed that some individual organisms
are able to survive better than others.
He felt that
this was
because of
certain
traits that
they possess.
Darwin found that
animals with
favorable traits live to
pass them on.
He called this the theory
of Natural Selection
This is also known as the
“survival of the fittest”
The five factors Darwin
identified that govern
natural selection are:
1. Organisms
produce more
offspring than can
survive
2. Individuals of a
species vary (in size,
speed, color, etc.)
3. The environment
contains things that
kill organisms
4. Some variations
are better for survival
and reproduction
than others
5. Over time,
organisms with better
traits make up more
of the population
One of the points in Darwin’s theory of
evolution is that variations are found
among individuals of a species.
A variation is the appearance
of an inherited trait that makes
an individual different from
other members of the same
species.
(A species is a group of organisms whose
members successfully reproduce among
themselves)
Variations can be small (such as the
differences in human hairlines),
or large, such as a fruit without seeds.
Variations are important in
populations of organisms.
A population is a group of organisms of
one species that live in an area.
If enough variations occur in a
population as it produces new offspring,
a new species may evolve from the
existing species.
It may take
hundreds,
thousands, or
even millions
of generations
for a new
species to
evolve.
Some variations are more
helpful than others.
• An adaptation is
any variation that
makes an
organism better
suited to its
environment
Desert Fox
Arctic Fox
The variations that result in
adaptation can be in an organism’s
color, shape, behavior, or chemical
makeup.
Camouflage is a protective
adaptation that lets an organism
blend into its environment.
An organism whose color or shape
provides camouflage is more likely
to survive and reproduce.
These types of variations result from
mutations, changes in an organism’s
DNA. Mutations are the source of
variation among organisms.
How fast does evolution occur?
Scientists are debating that question. Most
scientists hypothesize that evolution occurs
very slowly, perhaps taking tens or
hundreds of millions of years.
Other scientists hypothesize that
evolution may occur very quickly,
perhaps in a million years.
Darwin
hypothesized
that the rate
of evolution
was steady,
slow, and
continuous.
The model that
describes
evolution as a
slow change of
one species to
another new
species is
called
gradualism
In this
theory, there
should be
intermediate
forms of all
species
However,
gradualism
doesn’t explain
the evolution of
some species,
especially those in
which few
intermediate forms
have been
discovered.
Another model, the
punctuated
equilibrium model,
shows that rapid
evolution of species
can come about by
the mutation of just
a few genes.
New species
could appear
as quickly as
every few
million years,
and sometimes
even faster.
Antibiotics have only been available
for about 50 years, and in that time,
many bacteria have become resistant
to this form of treatment.
Some bacterial strains have
evolved quickly, which is an
example of punctuated
equilibrium. Mutations produce
large changes in a short period of
time.
Coevolution happens when two or
more organisms evolve together.
Example #1: Pacific snails have stronger shells
than Caribbean snails. Pacific crabs, which eat
snails, have also evolved stronger claws than
Caribbean crabs to crush the snails.
Coevolution happens when two or
more organisms evolve together.
Example #2: Cabbage plants evolved a way to
produce mustard oil, which is a poison to
most insects. However, cabbage butterfly
caterpillars have evolved a way to break down
mustard oils.
Coevolution happens when two or
more organisms evolve together.
Example #3: The trees that giraffes feed on
have evolved long spines. In turn, giraffes have
evolved a long, very tough tongue.
When a species cannot
adapt to the
environment quickly
enough, it becomes
extinct.