natural selection - rudy and perez biology -...
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Natural Selection Review Questions
1. What traits were favored by the female cricket?
2. When it came to the crickets, what does fitness mean?
3. How was nature selecting for the fittest cricket in the cartoon?
Lamark
A. Lammark (early 1800s) believed
organisms evolved through inheritance of
acquired characteristics.
B. However, the inherited characteristics
were modified during your lifetime and
the modifications could be passed onto
your offspring.
• Next, let’s look at 2 examples of
Lammark’s ideas.
Lamark
Example1:Giraffes
stretched out their necks to
reach leaves on tree tops,
and the stretched neck
was inherited.
Example 2: A
father that
pumps iron will
produce a body
builder offspring.
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.
So in 1858,
Darwin and
Wallace
submitted
separate
papers to the
Linnaean
Society in
London.
OH! BETTER TURN IN MY PAPER NOW!
• In 1859 Darwin published his book “On
the Origin of Species”
*Darwin’s ideas are the basis of the theory of
evolution. He not only provided evidence
for how organisms change throughout time
but why they change.
CHECKPOINT • Which scientist established that all
species of life have descended over time from common ancestry, and proposed the scientific theory of evolution?
a) Alfred Wallace
b) Jean Baptiste Lamark
c) Charles Darwin
Darwin’s 4 Postulates
1. Individuals in a population differ from
one another. (Diversity or Variation)
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 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.
CHECKPOINT
• Will all the lion cubs survive?
No, Darwin’s 3rd postulate
explains that more offspring are
produced than survive.
Natural Selection • Adaptations are inherited
characteristics that give organisms an
advantage in their environments.
• Over time adaptations can change.
• Natural Selection explains the
changes in populations over time.
Natural Selection
• Natural selection is a
mechanism of evolution,
meaning it causes
evolution.
• It causes changes in allele
frequencies over time.
• Remember an allele is one
form of a gene. (G or g)
Natural Selection
Remember that natural selection chooses
traits that are best for a particular
environment. Nature does not create
prefect individuals nor does it give organisms what they need.
Giraffe’s long necks are
_______ for eating leaves
up high!
Giraffe’s long necks are _______
for drinking because it causes
them to be vulnerable to
predators.
CLICK HERE TO WORK AN EXAMPLE!
CHECKPOINT
ADAPTATION
GOOD OR BAD?
• Remember that natural
selection selects/works on
individuals.
• For, evolution to occur the
population must change
over time.
• Meaning the individuals must
pass their traits on to the next
generation.
Natural Selection
• Individuals do not change when selected.
• By passing on genes that confer an
advantage, they can cause the population
to change.
• The number of the advantageous alleles
becomes more frequent.
Natural Selection
NATURAL SELECTION NOTE PROCESSING
• Follow along the simulation of natural selection.
• http://www.sciencenetlinks.com/interactives/evolution.html
Which alleles are more frequent? GG or gg
Did the Allele frequencies change over time? Y N
How many green beetles?
How many orange beetles?
10 6
Did natural selection cause evolution? Y N
Which genotype would have an advantage in a
changing environment? GG Gg or gg
Artificial vs. Natural Selection
• Artificial selection
is also known as
selective
breeding.
• Example: Humans
pick 2 dogs with
desirable traits
and breed them.
•Natural selection
occurs when nature
picks 2 organisms with
desirable traits and
allows them to
successfully
reproduce.
Natural Selection Experiment
• Anolis Sagrei Lizards were removed from
their home of many trees and released
onto 14 small islands that had few trees.
• Researchers returned 14 years later to
discover that the lizards had evolved
shorter, thinner legs. (No longer adapted
for tree life)
CHECKPOINT
• Artificial or Natural Selection?
Artificial Selection – farmers
cultivated crops by selecting
certain attributes of the wild
mustard.
Patterns of Natural Selection
Directional
Selection
• Selects
extreme value
•Example:
Longer nose of
anteater is
selected for.
Stabilizing Selection
•Favors average value
•Example: Small lizards
can’t defend territory
and large lizards are
easily eaten, so
average size lizards
are selected for.
Disruptive Selection
•Favors both
extremes
•Example: Light
and dark clams
survive better in
light and dark
sand. The yellow
can’t blend.
Humans Impact and Evolution
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.