Classwork: Evolution and Natural Selection
Group ____405_ __Name _____Valeria Elizondo A01194577 Vera Marcos A01194537
Introduction
Different individuals in a population have different characteristics. This is known as variation.
Some of the variations in characteristics can be inherited by a parent’s offspring; and they are
called heritable characteristics. Some characteristics make individuals better at surviving and
reproducing than others. Fitness refers to the ability to survive and produce offspring that are
capable of reproducing. The specific characteristics that contribute to fitness will differ in
different environments.
A characteristic that increases an individual’s fitness is called an adaptation. Notice that
biologists use the terms adaptation and fitness to have different meanings other than the
common meanings of these words in everyday language. Living things that are well adapted
to their environment survive and reproduce, while those that are not well adapted do not. An
adaptation is considered any characteristic that increases fitness, which is the ability to
survive and reproduce.
Heritable adaptive characteristics become more common in a population over many
generations. This process is called evolution by natural selection. Evolution by natural
selection is a gradual process that takes place over many, many generations. Evolution by
natural selection results in changes in the frequency of characteristics and alleles or genes
within a population, and not changes in an individual.
Which characteristics are adaptive and how a population evolves depends on what kind of
environment the population is in. The same population will evolve differently if placed in a
different environment. Organisms are not evolving to some pre-ordained “perfection” but are
evolving to maximum fitness in a given environment.
Instuctions:
1. Study figures 1- 3 below, then answer the questions using these figures:
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a) Is the population of mice found in figure 1 different that the population of mice found
in figure 3? Explain why.
Yes, the white mice are disappearing and the grey mice are surviving with each
generation because they camouflage.
b) What characteristic of the mice is an adaptation that increased their fitness?
Their grey color increased the fitness in an adaptation way.
2. Using your observation of figures 1-3, apply the scientific method to do the following
a) Write an investigation problem:
b) State your hypothesis:
c) Define the variables:
a. Independent: The color of mice
b. Dependent: the number of mice
c. Controlled: The color of soil
3. The table below gives descriptions of four female mice that live on a beach that is mostly
tan sand with scattered plants: Using the table above, answer the following questions:
Fur color
black
tan
Tan and black
cream
Age of death
2 months
8 months
4 months
2 months
# of pups
produced by
each female
0
11
3
0
Running speed
8 cm/sec.
6 cm/sec.
7 cm/sec.
5cm/sec
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a) According to the definition of fitness, which mouse would biologists consider the
fittest? Explain why.
The grey mice are the fittest, because they can camouflage in the soil and it makes
them survive.
b) If the mouse´s fur color is generally similar to its mother´s color, what color fur would
be most common among the pups?
Their most common color is the grey because of evolution by natural selection, that
means that they survive longer with a grey color fur because they camouflage with the
soil, and they are more probable to be born with their mother`s color that is more
probable to be the survival color.
4. Below is a series of pictures representing changes in a population of cacti. Pictures 1 and 2
show what happened when a deer came to eat, picture 3 shows the cacti a few weeks
later (notice the flowers on the right-hand cactus), and picture 4 shows the situation a few
months later. Use these pictures to answer the following questions:
a) One characteristic that is necessary for natural selection to take place is variation in
characteristics within the population. In picture 1, what is the main difference
between the cactus on the left and the cactus on the right?
The difference is that one cactus has thorns and the other doesn’t.
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b) Another characteristic necessary for natural selection to take place is differences in
survival and reproduction fitness. Why would a deer be more likely to eat the cactus
on the left than the cactus on the right?
One cactus has thorns and that make that cactus to survive more, because animals
wouldn`t eat them because it will harm them, but the other cactus doesn’t has thorns
so it makes it more a victim and in this example, victim of the deer.
c) What effect does the deer´s behavior have on the survival and reproduction of these
two types of cactus?
The deer is eating the cactus without thorn so they are becoming more extinct, and
the cactus with thorns are surviving and reproducing.
Another characteristic necessary for natural selection to take place is the heritability
of characteristics from parent to offspring. The difference between the cacti is a
heritable characteristic (see picture 4). Do you think that evolution by natural
selection is occurring in this population? Explain why or why not.
Yes because of the evolution by natural selection so the ones that have thorns are
being reproduced can survive more.
Evaluation
Criteria
3
2
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Interpretation of
figures 1-3
All questions
related to the
figures were
answered correctly.
All questions
related to the
figures were
answered, but some
of them were not
answered correctly.
All questions
related to the
figures were
answered, but none
of them were
answered correctly.
The investigation
problem,
The investigation
problem,
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Steps in the
scientific method
The investigation
problem,
hypothesis and
variables were all
correct and were
appropriate for the
information given
in the figures.
hypothesis and
variables had some
mistakes, but were
appropriate for the
information given
in the figures.
hypothesis and
variables had some
mistakes, and were
not appropriate for
the information
given in the figures.
Data interpretation
Both questions
pertaining to the
data chart were
answered correctly
One of the
questions
pertaining to the
data chart was
answered correctly.
None of the
questions
pertaining to the
data chart were
answered correctly.
Understanding the
conditions
necessary for
natural selection to
take place
All questions
pertaining to
natural selection
were answered
correctly.
Some of the
questions
pertaining to
natural selection
were answered
correctly.
None of the
questions
pertaining to
natural selection
were answered
correctly.
Team work
The team members
worked together to
do the activity.
They turned it in on
time.
The team members
worked together to
do the activity.
They didn´t turn it
in on time.
The team members
didn´t work
together to do the
activity. They
didn´t turn it in on
time.
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