Download Natural Selection Example 2

BIOSCIENCE 03 – Organismal Biology
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Lab Assignment #: 2
Team Name:BSers (BrainStormers)
Lab Assignment Title: Natural Selection
Date: 20150212
BACKGROUND:
● Natural selection is a process in which individual organisms that have certain inherited traits tend
to survive and reproduce at higher rates than other individuals because of those traits, as given
by Campbell.
● Natural selection is considered a mechanism for evolution, which can be defined as the change in
the frequency of genetic traits in a population over time.
● Selective pressures have played a part in natural selection to determine which populations are
best suited for specific environmental conditions.
● Charles Darwin and Alfred Russell Wallace outlined several requirements for natural selection to
occur, including heritable variation within the population, the presence of more individuals than
the environment can support, and an environment that favors certain traits in the population over
others (see Campbell reference).
○ If all these conditions are present, individuals in the population that have favored traits
are more likely to survive and reproduce, and thus pass down those traits to their
offspring.
● We know that the environment selects for different traits, and is a mechanism of natural selection.
● Co-evolution dictates that predators that are more able to take advantage of a prey’s adaptations
are more likely to evolve, perpetuating a phenotypic “arms race.”
PURPOSES/OBJECTIVES:
● Evolution through Natural Selection is a continuous process; we want to observe how phenotypic
traits can affect the rate of survival (see reference 2).
● In this experiment, we will simulate natural selection under simple factors and different
environments in a laboratory model and we will track the frequency of heritable traits in predator
and prey populations over several generations.
BIOSCIENCE 03 – Organismal Biology
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HYPOTHESES:
● Predators are a major selective pressure on populations, making prey who are better adapted to
survival likelier to reproduce. Phenotypes that thrive will propagate more readily than those that
have a disadvantageous phenotype.
● For a simple model where the environment has distinct boundaries, individuals who blend into
their surroundings and stay along the edges of the environment will, after several generations,
become more predominant over individuals that do not blend as well.
● The brightly colored individuals will flourish in bright environments, while dark colored species will
survive better in darker environments.
● When species of the same color are clustered together, they become a more obvious target for
predators and will therefore die out faster. Species that spread over a larger area will have a
higher likelihood of survival and propagation.
● Predators will adapt alongside their prey, preferring advantageous mutations/behaviors, similar to
what happens in populations of prey.
SPECIMENS
● 40 paper dots each of 8 different colors to represent the species population in natural selection
(prey)
MATERIALS:
● 40 paper dots, each of 8 different colors
● 2 different colored fabric boards
INSTRUMENTATION:
● 8 clear plastic cups
● 2 predator cups
● 1 playing card
METHODS/PROCEDURES:
● We used the following equation to calculated the compound average rate of growth percent
(CARG%), which tells us the average rate of growth if we carried the experiment into further
generations.
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We used the following equation to calculate the percent change in the population of each species.
BIOSCIENCE 03 – Organismal Biology
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Spring 2015
11497 5 Units
VJOCTR 242 / 207 / FIELD
TTh 1:00 PM – 2:15 PM LEC
TTh 2:30 PM – 5:20 PM LAB
DEKLOE / RIDDELL
Obtain 40 paper dots per person of 8 different colors (to resemble different species) and placed
each set of colors in the clear plastic cups provided by the instructor.
The instructor will provide a colored fabric board that closely resembles the traits of the
population species (this will act as the environment).
For the first generation, each person must place 20 of their colored dots (prey) onto the the
environment.
For the second generation, a person from our table served as the “predator” and removed the
“prey” (using only his index finger and thumb) from the environment for 75 seconds- simulating
the mechanism of natural selection.
Count the number of prey that was removed from the environment and record the data.
The number of surviving dots reproduced and there count was doubled.
The maximum carrying capacity of the environment for each species is 40.
For the third generation, a person from another table served as the predator and used an index
finger and thumb.
For the fourth generation, the environment was replaced (see “Environment 1” from the
“Attachments” section). A person from another table served as the predator and used an index
finger and thumb from both hands.
For the fifth generation, two people from another table served as the predators and used their
index fingers and thumbs from both hands.
In the fifth generation, a thunderstorm was simulated by flicking the lights on and off, in order to
mimic a natural disaster to give the predators a disadvantage similar to what would happen in
nature.
For the sixth generation, the instructor used a playing card to randomly wipe away some of the
colored dots to simulate the impacts of natural phenomena.
In the event that an entire species was wiped out, the species were to restart the new generation
with 20 dots.
We saw this in generation 5, when the green dot population went extinct and a blue dot
population was introduced.
Overall, as the generations passed, the predators became stronger.
RESULTS:
● We found that the green and pink species did not do well in the first environment.
● When clustered together, species of the same color died out faster and were unable to survive
and reproduce as much as the rest of the species present.
● In the second environment, when the predators attacked, we found that green, orange, yellow,
and pink either died off or very few were left.
● According to Figure 1 (Populations with Projected Decay), the population counts in the first 6
generations fluctuated, but mainly had decreased in numbers.
○ It illustrates the population counts when forecasted up to generation 12; essentially, all of
the species had a declining logarithmic trend line.
BIOSCIENCE 03 – Organismal Biology
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○
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It exhibits the concept of natural selection; species who are unfit for survival from
predators continued to decrease.
Figure 2 (Populations with Projected Growth) essentially shows the forecasted trend lines for the
light purple and aqua (introduced in generation 4 after the green species died out) species; they
have increasing trend lines.
○ It illustrates the concept of natural selection in such a way that species who evaded the
predator were able to survive and reproduce more successfully than the other species
who weren’t able to hide.
Figure 3 ( Population Data with Projections) displays the combined representation of all of the
species; there is a definite decline in population size of each species for generations 1 through 6
for the orange, yellow, and green species and a definite increase in population sizes for the light
purple and aqua species.
Figure 4 (Population Size) presents the overall population counts from generations 1 to 6; in
generation 3 and generation 4, the population counts reached their highest numbers.
○ Light purple and aqua were the only species to achieve higher numbers at the end of
generation 6.
Figures 5, 6, 7, 8 essentially depicts the percent compound average rate of growth to show the
measure of growth for the 12 generations.
ANALYSIS/DISCUSSION:
● Natural selection can be caused by natural adaptations and extinctions or manipulation by human
intervention.
● By simulating selective pressures, natural selection can be replicated in a laboratory setting.
● Species (light purple) that hid along the edges of the environment and species that blended into
the colors of the environment were successful in surviving and reproducing.
● Some predators adapted to certain kinds of prey, specifically selecting certain colors of dots.
● Some colors were visible better in the first environment, whereas other colors stood out more in
the second; this had a direct impact on the survival rate, as the more visible ones were “eaten” at
a higher rate.
● Adaptations take place in both the predator and the prey, as the population size of each species
for generations 1 through 6 adapts to better protect itself from danger. The predator targets the
less developed prey and over generations adapts to their prey’s changes, sometimes specific to a
certain adaptation.
● As the environment changed, some species that thrived in the previous background suffered an
utter extinction while others who were previously the minority became the majority.
● The sudden environmental change lowered the survival rate for many species.
● When a specific species did not diversify within its environment, that species was more likely to
become extinct.
● The natural environment “selects” for specific traits in certain environments. The ability of the blue
dots to thrive in the first environment, yet diminish in size in the second environment
demonstrates this concept.
● The bottleneck effect favors the most abundant population after an extinction event.
BIOSCIENCE 03 – Organismal Biology
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Spring 2015
11497 5 Units
VJOCTR 242 / 207 / FIELD
TTh 1:00 PM – 2:15 PM LEC
TTh 2:30 PM – 5:20 PM LAB
DEKLOE / RIDDELL
Natural selection is differential success in reproduction, which is the unequal ability of species to
survive and reproduce. The increase of the favored traits in a population is evolution.
Survival is linked to frequency of reproduction, perpetuating beneficial mutations and weeding out
the disadvantageous mutations.
We can say that our hypothesis has not been disproven by our results; our data heavily supports
our hypothesis. However, further experiments are necessary to further support our hypothesis.
We learned that we can simulate natural selection in an artificial environment to a certain extent.
This experiment allows us to further understand what happens to populations in a natural setting,
and how their survival will be affected over future generations.
CONCLUSIONS/FURTHER CONSIDERATIONS:
● We witnessed a simulated process of natural selection. Now the question remains of how much
of our results can be translated into real processes of natural selection.
● This experiment did not take the ability of prey to adapt into consideration. The predators
adapted over generations, however, the prey did not adapt to the changing threat of predators.
● Our simulation of natural selection was performed under a very basic set of circumstances. In
order to further understand natural selection we need to perform other experiments with more
complex environments and different kinds of predators. This might exhibit a greater diversity of
results.
● It would be interesting to repeat this experiment under the same conditions with other persons
acting as the predators. We would ask the question: did some of our predators show a preference
for a certain species that went beyond the ability to spot the prey?
BIOSCIENCE 03 – Organismal Biology
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ATTACHMENTS
TABLE 1: SUMMARY OF SPECIMENS
Prey
(40 dots per species)
Predator(s) (randomly selected students that
were given behavioral instructions)
Blue
(2) 1 index finger and 1 thumb
Light Purple
2 sets of index fingers
Orange
4 sets of index fingers and thumbs
Yellow
Green
Dark Purple
Pink
Aqua
BIOSCIENCE 03 – Organismal Biology
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TABLE2: SUMMARY OF METHODS AND PROCEDURES
Generation
Natural Selection
Mechanism
Time Limit
(seconds)
Environment
1
None
75
1
2
1 index finger and 1
thumb
75
1
3
1 index finger and 1
thumb
75
1
4
2 sets of index fingers
and thumbs
75
2
5
4 sets of index fingers
and thumbs
75
2
6
Playing card
75
2
BIOSCIENCE 03 – Organismal Biology
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TABLE 3: SUMMARY OF POPULATION COUNTS OVER 6 GENERATIONS
Populatio
n Size
Data
G1
G2
G3
G4
G5
G6
Blue
20
28
40
28
12
13
Light
Purple
20
33
40
37
28
40
Orange
20
35
40
40
1
1
Yellow
20
32
40
32
1
0
Green
20
16
20
16
0
0
Pink
20
21
13
16
9
13
Dark
Purple
20
29
40
24
9
9
Aqua
0
0
0
0
20
24
BIOSCIENCE 03 – Organismal Biology
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Spring 2015
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FIGURE 1 This figure plots population size vs. generation for all species in our experiment that had
decreasing trend lines.
BIOSCIENCE 03 – Organismal Biology
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FIGURE 2 This figure plots population size vs. generation for all species that had an increasing trend
line.
BIOSCIENCE 03 – Organismal Biology
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FIGURE 3 This graph plots the population size vs. generation for all of the species in our experiment
out to the 6th generation. The dashed lines are logarithmic trend lines that show the estimated values
for the population size of each species out to the 12th generation.
BIOSCIENCE 03 – Organismal Biology
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FIGURE 4 This figure shows the population size of each species for generations 1 through 6.
BIOSCIENCE 03 – Organismal Biology
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FIGURE 5 This figure plots the percent change in population size for each species using the raw data
we collected through experimentation. Note that there are three comparisons for each species in this
figure, generations 1 & 3, 4 & 6, and 1 & 6.
BIOSCIENCE 03 – Organismal Biology
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FIGURE 6 This figure shows three compound average rate of growth values for each species using
only the raw data we collected through experimentation.
BIOSCIENCE 03 – Organismal Biology
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FIGURE 7 This figure shows two compound average rate of growth values for each species. On the
left, we used data obtained through our logarithmic trend lines. On the right, we used our raw data
along with our trend line data.
BIOSCIENCE 03 – Organismal Biology
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FIGURE 8 This figure shows the compound average rates of growth for different sets of generation
s.
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Environment
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Images
Environment 1
Environment 2
References
1. Reece, J. (2011). Campbell biology Jane B. Reece ... [et al.]. (9th ed.). Boston: Benjamin
Cummings.
2. The Paleontological Research Institution and its Museum of the Earth. Types of Natural
Selection.
NY. Paleontological Research Institution. [cited 2015 Feb 19]. Available from
http://bivalves.teacherfriendlyguide.org/