Part A
An organism’s adaptations are specific to its native environment. An organism that lives in a coniferous forest will have different adaptations compared to an animal that lives in a tropical rain forest. The following graphs show the temperature and precipitation throughout the year for two different forests: a coniferous forest in Canada, and a tropical rain forest in Belize.
Evaluate the graphs, and then explain why plants from these two ecosystems will have different adaptations. In your answer, explain the survival challenges that plants face in these two environments.
Coniferous Forest
graphical representations of the temperature and precipitation in a coniferous forest from January to December
Tropical Rain Forest
a graphical representation of the temperature (top image) and precipitation (bottom image) in a tropical rain forest from January to December
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Part B
Many rain forest plants are prone to developing fungal infections on their leaves. Fungi can grow rapidly in moist environments, and a serious infection can kill plants. One rain forest plant species has a genetic variation that affects its leaf structure. The traits and the descriptions of the plant’s leaves are listed in the chart.
Description
Trait A: medium-tip leaves Leaves are narrower toward the tips, but don't come to a full point. Most of the water drains from the leaves.
Trait B: drip-tip leaves Leaves come to a sharp point, leading to thorough water drainage from the leaves.
Trait C: wide-tip leaves Water runs onto the leaves and tends to pool in pockets at the tips.
During natural selection, organisms with harmful traits are less likely to successfully reproduce than organisms with beneficial traits. Neutral traits don’t improve or hurt an organism’s chances for survival. So, they tend to persist in populations when environmental conditions are stable. If the environment changes, neutral traits could become harmful or beneficial depending on the situation.
In year 1, a population of rain forest plants has the following distribution: 50% have medium-tip leaves, 25% have wide-tip leaves, and 25% have drip-tip leaves. You will simulate three years of this population: year 1, year 5, and year 10. How will the trait distribution most likely change over this time?
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Part C
Question
You will build a simulation of a population using the same elements as the simulation pictured here and show how the traits in this population change in years 5 and 10.
several red, blue, and green circles representing different traits in a population, with one circle being equivalent to 50 organisms
Start off with 2,500 plants of which 50% have medium-tip leaves, 25% have wide-tip leaves, and 25% have drip-tip leaves. Each circle in your simulation will represent 125 organisms. Calculate how many circles you need for each trait, and then create your simulation. Be sure to include a key that states the color coding for each trait.
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Part D
Question
Next, you’ll build a simulation based on what you think will happen because of natural selection.
Here are two considerations:
Some individuals with harmful characteristics can still successfully reproduce, but they have an overall lower chance of doing so compared to organisms with neutral or beneficial traits.
Natural selection may affect distribution of traits. It’s possible that harmful traits could eventually disappear from the gene pool.
Don’t worry about precise population numbers. Based on your understanding of natural selection, you’ll be modeling only one scientifically plausible trend that can occur. There are several correct variations of this diagram. You’ll explain the justification for your choices in part E.
Assume that these plants have a life expectancy of about one year, but the rate of reproduction keeps their population consistently around 2,500 organisms. Using the same elements you used in part C, draw simulations for year 5 and year 10. Clearly label each simulation.
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Part E
Explain your justification for the changes in trait distribution between years 1 and 10. What do you think will happen to the population by year 15?
