Download Martian Natural Selection

Change Over Time
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State Standard:
H.2L.4 (b, e) -- Explain how biological evolution is the
consequence of the interactions of genetic variation, reproduction and
inheritance, natural selection and time.
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4
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Scoring Rubric
Evaluate the impact of the interactions of genetic variation, reproduction and inheritance, natural
selection and time on biological evolution (change)
Explain how biological evolution is the consequence of the interactions of genetic variation,
reproduction and inheritance, natural selection, and time, using multiple lines of scientific evidence.
Describe the process of biological evolution through natural selection
Recognize that species have changed over time
Did not participate
Score
Martian Natural Selection
Natural selection is the survival of the fittest organism. Charles
Darwin observed four major points about natural selection: 1. more
offspring are produced then can survive, 2. in any population, variation
exists, 3. some variations are favorable, 4. those with favorable
variations survive and reproduce. But what makes an organism most fit?
In this activity, you'll investigate natural selection and the pressures
driving the potential changes in the population's gene pool.
Problem: What is natural selection?
Materials: penny, beans, tray, forceps, wood splints, straw, clothespin, paper plate
Part A. Genetic Drift
Background: In small populations that interbreed, such as certain religious groups, royal families and
isolated populations, gene pools change quickly because the number of potential mates is limited.
Mistakes in meiosis (formation of male and female gametes) can result in genetic drift (a shift in the
gene frequency w/in a population). In Part A, you will flip a coin to show how small populations can be
affected by genetic drift and answer the questions.
Procedure:
Table 1
a. Flip a coin 100 times and record the number of heads and
100 flips
10 flips
tails in the data table 1. The result will probably be close to 50Heads
Tails
Heads
Tails
50.
b. Next, flip a coin 10 times and record the number of heads
and tails in the data table 1.
%
%
%
%
Analysis:
1. If you flip a coin 100 times, are the chances likely or unlikely
that you'll get 100 heads and 0 tails? ____________. What about 80 heads and 20 tails?
_______________.
2. If you flip a coin 10 times, are your chances better or worse in getting 10 heads and 0 tails - or
even 8 heads and 2 tails? _________________
3. Describe the genetic drift in terms of % change from 100 to 10 flips.
Part B Mutation
Background: It's happened. NASA has successfully landed on Mars. Twelve astronauts have
established the first colony on the Red Planet. Or, at least that is what we thought. Much to the
surprise of the astronauts, Mars was already inhabited! Martians run amuck in thousands of
underground tunnels unseen from Earth's telescopes. The astronauts learned a valuable lesson when
they entered the first underground village. Apparently, the protein melanin, which is embedded in
human skin and controls pigment, causes the Martian's green skin to mutate and turn purple on
contact. So, every time the astronauts shook hands with a Martian, their skin proteins mutated and
changed color!
s
S
Analysis:
4. Purple skin (S) is dominant to green skin (s). Predict the
S
probable genotypic and phenotypic ratios in the
future generations within the mutated population of Martians.
Genotypic
______ : ______: ________
Phenotypic
__________: _________
s
Part C Natural Selection
Background: There have been three different species discovered on Mars, each living in their own
population. These species all compete for the same food resource, a type of bean grown under the
Martian clay. Each species have different mouth parts that enable them to pick up beans to eat.
Some Martians have clothespin mouths, some have tweezer mouths, and some have chop-stick mouths.
Humans need to eat as well and have used their giant brains to devise an efficient manner of bean
gathering - spoons!
Procedure:
a. Martians only emerge for 30 second intervals to feed. Each Martian or human must collect 10
beans in order to survive and reproduce. Both are full after 15 beans and stop eating. Place the
collected beans on the plate provided and start the trial. Each organism feeds separately.
b. Record the collected number of beans in the table 2. Repeat for the next generations.
c. Count the total beans taken by each organism and calculate an average.
Table 2
Time
(Gen).
Trial 1
Tweezer
Beans collected
clothespin
Chopsticks
Trial 2
Human
spoon
Tweezer
Trial 3
Beans collected
clothespin Chopsticks
Human
Tweezer
Beans collected
clothespin
Chopsticks
Human
spoon
P
F1
F2
Total
Avg.
Analysis:
5. What happens to animals that cannot compete as well with others in the wild?
6. If only one species is considered the "fittest", why do we still have so many variations among
species? Why do some birds have very long pointy beaks, while other birds have short flat beaks?
7. Label the graph Directional, Disruptive, or Stabilizing Selection and circle which type of natural
selection was on display in Part C.
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