natural selection.docx - napa valley college 112... · web viewnatural selection is considered a...

BIOSCIENCE 03 – Organismal Biology Session:Section:

Class Location:Days / Time:

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Spring 201511497 5 UnitsVJOCTR 242 / 207 / FIELDTTh 1:00 PM – 2:15 PM LECTTh 2:30 PM – 5:20 PM LABDEKLOE / RIDDELL

Student Author Name: Team Members Names:Spring

Student Author ID #: Team Members ID #’s:

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.



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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.

●

● We used the following equation to calculate the percent change in the population of each species.



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● 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.



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● 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.

○ 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.



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● 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.● 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?



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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



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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



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TABLE 3: SUMMARY OF POPULATION COUNTS OVER 6 GENERATIONS

Population 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



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FIGURE 1 This figure plots population size vs. generation for all species in our experiment that had decreasing trend lines.



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FIGURE 2 This figure plots population size vs. generation for all species that had an increasing trend line.



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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.



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FIGURE 4 This figure shows the population size of each species for generations 1 through 6.



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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.



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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.



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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.



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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 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/



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