Download natural selection 1

Take notes 1. What is the definition for natural selection given
on page 463?
2. What do they mean by “No such thing as
perfect” in Figure 16-11?
3. Look on page 460 and write down the
conditions under which natural selection will
occur.
4. What is meant by struggle for existence?
5. Why must a beneficial trait be “heritable” for it
to drive evolution?
6. What are the three adaptations shown in the
photos on page 461?
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Individual Guided Reading Page 482483
What is the main point of the THINK ABOUT IT paragraph?
What do you think is meant by, “Variation is the raw material for
natural selection?”
An organism’s genotype is the particular combination of ______ it
carries.
What is meant by the phrase, “Natural Selection acts directly on
phenotype, not genotype?”
(Page 483) In figure 17-2, what are the two alleles for fur color
present in the mouse population?
How many brown alleles are present in the population?
How many black alleles are present?
Is a “gene pool” something that an individual would have or
something that a population would have?
Read the last paragraph on 483 carefully. Explain in your own
words what is meant by “Populations, not individuals evolve.”
3 Sources of Genetic Variation
Single-Gene Traits
Polygenic Traits
Individual Notes
• (Page 488) Using the example in Figure 17-6,
explain how natural selection resulted in a
change in allele frequency in the lizard
population.
• (Page 489) Name and describe the three types
of natural selection that act on polygenic
traits.
Directional, stabilizing, or disruptive
selection?
• Along the Florida coast, light-colored oysters
are difficult for crabs to see because their
shells are almost the same color as the
limestone rocks. At the same time, darkcolored oysters are also difficult to see
because they blend into the shadows cast by
the rocks. In these areas, oysters that are
intermediate in color are preyed upon most
heavily by the crabs.
• Draw a graph depicting this type of evolution.
Directional, stabilizing, or disruptive
selection?
• Mice living on the island of Ubba Dubba range
in size from 4cm in length to 10cm in length.
Their size is a polygenic trait. The average size
in the 1920’s was 6cm. Today the average size
is 9cm.
• Draw a graph of this type of evolution.
Directional, stabilizing, or disruptive
selection?
• Robins typically lay a clutch of four eggs.
Research has shown that when robins lay
fewer than four eggs, there is a higher risk
that none of the offspring will survive and
reproduce as adults. Research also shows that
when robins lay more than four eggs at a time,
the babies tend to suffer malnourishment.
• Draw a graph of this type of evolution.
Genetic Equilibrium (Pg 491)
10,000 years ago
Present
How could each of these change the
genetic equilibrium of a population?
1. Natural selection:
2. Immigration/Emigration:
3. Mutations:
Small Population Size Can Change
Equilibrium Too!
Present
Genetic Drift
• Small populations only
(small sample size)
• Random chance causes
a shift in allele
proportions.
Sexual Selection
Name 5 things that drive evolution
The Process of Speciation
• (Page 494) How does one species become two
different species?
• What is reproductive isolation?
• (Page 495) What are the three kinds of
isolation that lead to speciation?
– Give an example of each
But how do the BIG leaps happen?
• (Page 500-501) Read the section on
Developmental Genes and Body Plans
• What is the significance of Hox genes in
evolution?