### Little snake, big gulp

This exercise is a part of Educator Guide: Snake Gulps and Chromosome Sequencing / View Guide

Directions for teachers:

Directions for students:

Watch this video and answer the “Before Reading” questions. Then read the online Science News article “A little snake’s big gulp may put all other snakes to shame” and answer the following questions as directed by your teacher.

1. Watch this video of a snake eating an egg. Describe the steps this snake goes through to eat this egg.

The snake opens its mouth wide to swallow the egg whole. Then, the snake waves back-and-forth, breaking the egg. Then the snake spits up the eggshell.

2. Which would surprise you more: an ant carrying an entire raisin or a squirrel carrying an entire raisin? Explain your answer.

Answers will vary. But probably, the ant would cause more surprise because it is smaller than the squirrel; therefore, its strength relative to its body size must be higher than the squirrel.

1. What is the scientific name of the Gans’ egg-eater snake?

Dasypeltis gansi is the scientific name of the Gans’ egg-eater snake.

2. Describe the three steps this snake uses to eat an egg.

First, the snake swallows the egg whole. Then, it uses its spine to crack the egg, digesting the contents. Finally, it spits the shells back out.

3. How wide in centimeters was the head of the biggest Gans’ egg eater snake that Bruce Jayne studied? According to Jayne’s study, approximately how wide of an object could this snake swallow?

The biggest Gans’ egg eater snake had a head about 1 centimeter in width. According to Jayne’s results, this snake could swallow a cylinder approximately 5 centimeters wide.

4. Describe the size of the petite Burmese python (Python molurus bivittatus) relative to the Gan’s egg-eater snake. How did the python’s gulp-size compare with that of the Gan’s egg-eater?

The petite Burmese python was about the same size as the largest Gan’s egg-eater. However, the gulp-size of the python was about 4.4 centimeters, which is smaller than the Gan’s egg-eater.

5. What does Jayne say about why the Gans’ egg-eater might have evolved its unique abilities?

Jayne says the Gans’ egg-eater may have evolved its large gulp-size because it eats eggs, which are short and round compared to other types of prey. Snakes with larger gulp-sizes would have an advantage because they could eat bigger eggs with more nutrients.

6. Why is a snake’s mouth size not a reliable indicator of gulp-size?

Some snakes have more stretchy tissue in their mouths, allowing them to open their mouth bigger.

7. Besides eggs, what is another snake dietary preference for which Jayne wants to study gape-size?

Jayne wants to study fish-eater snakes.

1. Consider the following statements: (1) That house is big. (2) That house is bigger than other houses on the block. Which one is an example of a relative comparison? How do these statements differ in what they communicate, and which is more informative? Explain.

Statement #2 is an example of a relative comparison. Statement #1 only says the house is big, whereas #2 says that the house is bigger than the houses around it. Statement #2 is more informative because it provides a scale to better understand what the term “big” means in this instance.

2. Use an example from this article to show the use of relative comparisons.

Comparing the gape-size of two species of snake is an example of a relative comparison from this article.

3. What measurements were used to quantify a relative comparison in the article? What units were used to make these measurements? Give the measurements from the article.

The measurements that helped quantify relative comparisons in the article were width of the snake’s head and width of a cylinder it could swallow. A unit used to make these measurements in this article was centimeters. A Gan’s egg-eater having a head width of about 1 cm could swallow a cylinder about 5 cm wide. The Burmese Python’s head width was also about 1 cm but could swallow a cylinder only about 4.4 cm wide.

4. Why might the author of a study choose to use relative values instead of other precisely defined units? How did the comparison help to give context to the research finding? Regarding the snake study, do you think the primary research paper reported the relative values, precisely defined values or both? Explain your answer?

Reporting relative values allows researchers to compare two values, making it easier to make sense of data and understand that the Gan’s egg-eater snake’s gape-size was relatively large compared to a snake with the same head width. The primary research paper likely gives precise measurements in a standard unit and relative values because the researchers must demonstrate how they compare the gape-sizes of different snake species.