Download Natural Selection - Northwest ISD Moodle

Procedures
• Get your journals. Find the classmate who has
the same number as you. They are your
partner for today – sit by them.
• Take out your chromebooks and go to
Socrative to take the evolution pre-quiz. This is
not a grade I want to see what your prior
knowledge is.
• Go to my Moodle page – Evolution toggle and
pull up the “natural selection” PowerPoint.
Natural Selection
Do bacteria change over time?
How do they change?
How do they become resistant?
Which bacteria will survive and
reproduce?
So over time, which bacteria will
be more abundant?
Lammark
• Pre-Darwin (early 1800s)
• Believed organisms evolved through
inheritance of acquired
characteristics.
• However you modify your body
during your life will be passed onto
your offspring.
Lammark continued
• Example1:Giraffes stretched out their
necks to reach leaves on tree tops,
and the stretched neck was passed
on.
• Example 2: A father that pumped iron
will produce a body builder baby.
Darwin and Wallace
Darwin wrote a
paper on his
thoughts of
evolution in
1842, but fear
of rejection
caused him not
to publish it.
In 1856 Darwin
received a
draft of a paper
written by
Wallace with
some of his
same ideas.
OH NO! I BETTER
TURN IN MY
PAPER NOW!
So in 1858
Darwin and
Wallace
submitted
separate
papers to the
Linnaean
Society in
London.
• In 1859 Darwin published his book “On
the Origin of Species”
* This is when we really started to study
and understand evolution!
Darwin’s 4 Postulates
1. Individuals in a population differ from
one another. (Diversity)
Darwin’s 4 Postulates
2. Some differences are due to
characteristics that are passed down
from parent to child. (Inherited variation)
Darwin’s 4 Postulates
3. More offspring are produced than
can survive, so some will survive and
reproduce and others will not.
Darwin’s 4 Postulates
4. Survival and reproduction depend on
advantageous traits. Those with traits that
give them an advantage will survive and
have more offspring than those that do
not have advantageous traits.
Natural Selection
• Natural Selection explains the changes
in populations over time.
• Natural Selection is also known as
descent with modification because
each species has descended with
changes from other species over time.
Natural Selection
• Natural Selection is also known as
“survival of the fittest” meaning that the
most fit organism in the environment will
survive .
• Fitness refers to an organisms ability to
survive and reproduce.
• Remember adaptations are
characteristics that give organisms an
advantage in their environments.
Remember that natural selection
selects for the best in context of a
particular environment.
Giraffe’s long necks
are good for eating
leaves up high!
Giraffe’s long necks are bad for
drinking because it causes them
to be vulnerable to predators.
http://www.sciencenetlinks.com/interactives/evolution.html
Remember that Natural Selection changes
the population not individuals.
• Individuals do not change when
selected, they produce more offspring
than others.
• Thus their alleles become more
frequent.
GREEN BEETLES- GG
ORANGE BEETLES- gg
Which alleles are more
frequent? GG or gg
How many green beetles? 10
How many orange beetles? 6
Which alleles are more frequent? GG or gg
Now, which alleles are more frequent? GG or gg
Which genotype would have an advantage in
any environment?
GG Gg or
gg
Evidence of Natural Selection
• Do you believe
in artificial
selection?
• Humans pick 2
dogs with
desirable traits
and breed
them.
•Why not believe in
natural selection?
•Nature picks 2
organisms with
desirable traits and
allows them to
successfully
reproduce.
More evidence :Experiment
• Anolis Sagrei Lizards were removed from
their home plentiful with trees.
• They were released onto 14 small islands
that had few trees.
• Researchers returned 14 years later to
discover that the lizards had evolved
shorter, thinner legs.
Selection can lead to 3
patterns of evolution
Directional Selection
Stabilizing Selection
• Selects extreme •Favors average
value
value
•Example: Small
•Example: Longer lizards can’t defend
nose of anteater is territory and large
selected for.
lizards are easily
eaten, so average
size lizards are
selected for.
Disruptive Selection
•Favors both
extremes
•Example: Light clams
and dark clams
survive better in light
and dark sand. The
yellow can’t blend in.
Humans can cause evolutionary events.
1. Our liberal use of pesticides has led
to resistant pests. So we are having
trouble protecting our food supply.
2. Our overmedication has led to
resistant “super-germs”. So diseases
are becoming more difficult to
treat.
3. Our heavy fishing has led to smaller
fish that slip through nets. So we not
able to extract as much food from
the sea.