Download Mechanisms for Evolution

Mechanisms for Evolution
Natural Selection
• Darwin found on his
journey that certain
animals were better
suited for their
environments than
other animals
• Darwin found that some
of these animals were
better suited to survival
than others
Natural Selection
• Darwin believed that
certain animals were
better suited to survival
and that helped them
live and have offspring
• Those animals that lived
and had offspring would
be the ones that you
see in the world
• This idea was called
natural selection
Natural Selection
• Natural selection can
only happen when one
organism has an
increased chance to
spread its genes
• The probability that an
organism will pass on its
genes to the next
generation is referred to
as fitness
Natural Selection
• An organism that has an
increase in fitness have
a larger chance of
passing on their genes
• An organism that has a
decrease in fitness has a
smaller chance of
passing on their genes
Overproduction
• There are also several
other things that
Darwin noticed during
his travels that helped
form his opinion of
natural selection
• One of the things he
noticed was the
number of offspring
that were produced
Overproduction
• Most animals can
produce more offspring
than can survive to
maturity
• This means that some
of the offspring will die
when they are young
• The offspring that will
die are ones that will
not be passing their
genes on in the gene
pool
Overproduction
• The idea that some
offspring do not survive
to maturity and cannot
contribute their
combination of genes is
called overproduction
• Examples of this would
be wild octopus
• More octopus are
produced each year
than can survive
Genetic Variation
• Darwin also noticed
that within a population
there are a difference in
traits
• The difference in traits
creates a full range of
traits within a species
• This is easy to observe
in any population
Genetic Variation
• The range of traits
within a population
helps determine how
natural selection
proceeds
• Natural selection tends
to select for certain
traits and have certain
other traits die out
• The range in traits is
called genetic variation
Genetic Variation
• The range in traits allows
for a species to survive if
some traits are not
variable
• If deer with large antlers
are hunted and killed
easier, there will be deer
that have small antlers
that would survive
• If there were no variation
among deer, none would
survive
Insert Graph of Height
# Of People
7
6
5
4
# Of People
3
2
1
0
4' 9"
5'
5' 3"
5' 6"
5' 9"
6'
6' 3"
Adaptation
• Some of the variations
help an organism
survive in an
environment
• These variations tend to
become more frequent
in a population
• The more frequent that
trait is in a population,
the better chance that
population will survive
Adaptation
• A trait that makes an
individual more likely to
survive in an
environment is called
an adaptation
• Something like thick fur
in a cold environment is
a successful adaptation
• Something like thick fur
in a warm environment
is not a successful
adaptation
Adaptation
• Remember an
adaptation is a
something that is
passed down from the
parents
• Adaptations are not
something that is
spontaneous or planned
by the organism
Artificial Selection
• What is the process that
Darwin proposed is the
driving force behind
evolution?
• Natural selection is a
process that occurs in
the natural world
• This means that no
human can interfere
Artificial Selection
• Sometimes humans
tamper with natural
selection
• This can be seen most
often in dogs
• Humans tend to want
dogs with certain
desirable traits
• They breed dogs together
that have these traits
Artificial Selection
• Artificial selection is
the process of humans
selecting individual
traits to give to the next
generation
• It is the only way that
we could have gotten
one of these from one
of these
Video
• Watch First!
• http://www.youtube.co
m/watch?v=nVSJNhUhV
-4
• Watch Second!
• http://www.youtube.co
m/watch?v=gxeD65E_A
vE
• http://www.youtube.co
m/watch?v=0zHnhbW0
8yQ