Download Shaping Evolutionary Theory – Chapter 15, Section 3

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Shaping Evolutionary Theory – Chapter 15, Section 3
Background Information:
According to the Hardy-Weinberg principle, a population in genetic equilibrium must meet five conditions…
1) There must be no genetic drift
2) There must be no gene flow
3) There must be no mutations
4) Mating must be random
5) There must be no natural selection
Instructions: Use your textbook to help you understand the consequences which result when each of the five conditions is
violated within a population.
What if there IS genetic drift?
Define genetic drift:
In ____________________ populations, enough alleles “drift” to ensure that the frequencies of alleles within the
population remain relatively constant from one generation to the next.
In ____________________ populations, the effects of genetic drift become more pronounced, and the chance of losing
an allele becomes greater.
Use your textbook to fill in the following chart on extreme examples of genetic drift.
Definition
Founder Effect
Bottleneck
What if there IS gene flow?
A population in genetic equilibrium experiences no gene flow, meaning that……..
In reality, why do most natural populations experience some amount of gene flow?
Real-Life Example
What if mating is NOT random?
Mating is completely random in a population in genetic equilibrium. Usually, mating is NOT random. Why?
What are the consequences of nonrandom mating?
What if mutations DO occur?
Define mutation:
Defend the following sentence: mutations provide the raw material upon which natural selection works.
What if natural selection DOES happen?
In a population that has reached equilibrium, all individuals in a population are ______________________ adapted to
their environment. This ( rarely / usually ) happens.
Natural selection alters phenotypes in three main ways:
1) Stabilizing Selection
2) Directional Selection
3) Disruptive Selection
Draw and label the graph for each type of selection and describe what is happening within the population.
Stabilizing Selection
During stabilizing selection……
Real-life example…..
Directional Selection
During directional selection……
Real-life example…..
Disruptive Selection
During disruptive selection……
Real-life example…..
Rate of speciation
Evolution is a dynamic process about which there is still much to learn. Many scientists are interested in studying the
rate of evolution. Describe the two theories which explain the possible rates of evolution….
1) Gradualism:
2) Punctuated Equilibrium:
Determine the theory represented by each image (gradualism or punctuated equilibrium).
Chapter 17 – Cladogram Practice
Background information: A cladogram, also known as a phylogenetic tree, is a diagram which depicts evolutionary
relationships between organisms. In the past, biologists would group organisms based solely on their physical
characteristics. Today, with the advances in genetics and biochemistry, biologists can look more closely at individuals to
discover patterns of evolution and group them accordingly.
Instructions: Examine the sample cladogram. Each letter on the diagram points to either the ancestral characteristic or a
recently derived characteristic. Ancestral characteristics are seen in the common ancestor and all recent organisms.
Derived characteristics are traits which appear in newer species, but not . Match the letter to its character. Note: this
cladogram was created for simplicity and understanding, it does not represent the established phylogeny for insects and
their relatives.
______ Wings
______ 6 Legs
______ Segmented Body
______ Double set of wings
______ Jumping Legs
______ Crushing mouthparts
______ Legs
______ Curly Antennae
1. Draw a star
at the location which represents the most recent common ancestor of ants and grasshoppers.
2. Defend this statement with facts: Butterflies are more closely related to dragonflies than spiders.
Refer to the cladogram below to answer the following questions:
B
3. What does the y axis represent?
D
C
E
F
G
4. Why does the line for species A
end before the top (now)?
A
y
5. Which species is the simplest?
How do you know?
J
H
I