Snail Kites are Snail Snackers

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In 1999, two researchers looked at the changes in population of a species of freshwater snails in Costa Rica. In this environment the snails have two main predators, both types of birds: the limpkin and the snail kite. In order to collect their data, the researchers looked at the leftover shells of the snails that had been eaten by these two birds.

They organized the shells according to two traits: size and color. The below image shows the shells in order of both size and color. The darkest and smallest is on the left and the largest and lightest is on the right.

The researchers found that limpkins hunted by walking around in shallow water. They would eat the snails by piercing the shells with their beaks, and would pile up the shells that they’d eaten. The below graph shows the frequency of different sizes among the piled shells the researchers found.

Snail kites locate their food from the air and use their special hooked beaks to pull the snails from their shells. To see their eating patterns, the researchers looked at shells that were not piled up and did not have a hole in them. The below graph shows the frequency of different colors of snails that had been eaten by snail kites.

References

Leavens, G. T. (2012). File:Aramus guarauna (Limpkin) 08.jpg. Wikimedia Commons. Retrieved November 8, 2022, from https://commons.wikimedia.org/wiki/File:Aramus_guarauna_(Limpkin)_08.jpg

Reed, W. L., & Janzen, F. J. (1999). Natural selection by avian predators on size and colour of a freshwater snail (Pomacea flagellata). Biological Journal of the Linnea Society, 67, 331-342.

Sanches, D. (2009). File:Flickr - Dario Sanches - GAVIÃO-CARAMUJEIRO (Rostrhamus sociabilis) (1).jpg. Wikimedia Commons. Retrieved November 8, 2022, from https://commons.wikimedia.org/wiki/File:Flickr_-_Dario_Sanches_-_GAVI%C3%83O-CARAMUJEIRO_(Rostrhamus_sociabilis)_(1).jpg

1. What type of snail was eaten the most by snail kites?

The somewhat dark snails.
The lightest snails.
The darkest snails.
The somewhat light snails.

2. Write a claim explaining the cause and effect relationship between the color of the snail’s shell and natural selection. Discuss how you would collect data to justify this claim. Be sure to identify whether the data you collect is qualitative and/or quantitative and why.

3. Explain the different genetic variations of the snails in this study.

4. If a snail lives longer, it’s to be able to .

Drag the answers below into the grey placeholders above

less likely

be eaten

pass on its genes

more likely

5. In places with a lot of snail kites, what type of snail is likely to live for the longest amount of time?

The lightest snails.
The darkest snails.
The smallest snails.
The largest snails.

6. What is the connection between the color of a snail and their ability to reproduce, when around snail kites?

7. What scientific ideas that aren’t described here explains what you see happening in the colors of the snails that are being eaten by snail kites?

8. Write a claim about how you expect the snail population to change over time, if snail kites continue their feeding patterns?

Only use this space to write a claim, we’ll ask you for evidence and reasoning in future questions. (hide hints)

9. What evidence supports your claim about how you expect the snail population to change over time, if snail kites continue their feeding patterns?

You should cite evidence from prior knowledge or the information presented here. (hide hints)

10. What reasoning helps to support your claim with the evidence you’ve cited?