Nocturnal Animals -
Grade Levels: 4-8
Purpose: To learn about some Adaptations of Nocturnal Animals to Living in the Dark
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1. Introduction: Ask the students if they know what nocturnal means. If they do not know what it is, start with the paragraph below. If they already have a general idea, start by having them brainstorm the names of a few nocturnal animals to get started, and then confirm their understanding with the paragraph below.
Nocturnal animals sleep during the day and are awake at night. They have special characteristics that help them get around in the dark. When you go into a darkened area, the pupil (or opening of your eye which appears to be black and lets in the light so you can see) changes to adapt to the reduced light. One of our activities explores what happens. Most nocturnal animals have special eyes that reflect the light to help them see. The pupils of nocturnal animals' eyes get larger to let in more light in darkness. Also, "behind each eye is a shiny surface, called a tapetum [tah-pee-tum] that reflects light like a mirror back into the eye. The yellow or orange 'eyeshine' is what we see when light catches the eye of a nocturnal animal." (1) Bats have a special sonar-like system to help them know where they are. They send a signal out in front of them. This signal will go forward and hit something, then come back. The bat can tell how far away the object is and what it was by analyzing the rebounded signal. This is called echolocation.
Next, Have the students pick partners. Then, hand out a sheet with the Activity Instructions found at the end of this page for the student teams to follow and to record their findings.
2. First Activity - If not done in partners, students will need mirrors to see their own eyes. Let everyone do the first part with the lights on, then switch the lights off (or so that they are very dim). Have them wait with their eyes open while the lights are off for a minute or two before their next observation. Have the student pairs jot down any observations they can make of how their eyes or vision was different with the lights off.
Then, Discuss in the larger group - See if any of the students have an idea as to why the pupil size was larger when the lights were off. After discussing, explain to them that because the pupil is the part of the eye receiving light, it will open wide when there is not much light so that it can receive as much light as possible in order to see.
3. Second Activity - This is also good to do in partners, or in small groups of 3 or 4. You will need tennis balls or ping pong balls, one for each group. Make sure there is enough room for them to safely toss the ball at a wall.
If you have a gym mat, padding, or a towel to lean against the wall, repeat the experiment #2, sonar, and ask the students to compare the sounding. If it is possible, this can also be done by tossing the ball lightly through an open door. Have the partner stand outside the room to retrieve the ball that leaves the room.
Following the activity, Return to the larger group for discussion: Have them discuss the results of their experiment. The tennis ball takes longer to return when they are further away, because it has a longer distance to travel. This is like the signal that a bat uses to find its way around in the dark. It sends out a signal, just as the students threw the ball. This signal bounces back to the bat so that the bat can sense it's surroundings. The bat can judge the distance and learn something about the object off which the sound bounced by the sound which is reflected.
4. Conclusion - What did the students learn from this lesson? For further enrichment, they can brainstorm and/or research the final questions. What else might an animal do to adapt to being awake at night? What are diurnal (awake in the day) and crepuscular (active at dawn and dusk, in the twilight hours) animals? They can research some examples of each to learn more and then share their findings about unusual or common animals.
Interact! Animal Crossword Puzzles # 7, 9, and 11-14 feature nocturnal animals.
Nocturnal Animals: Activity Instructions
Introduction: Nocturnal animals sleep during the day and are awake at night. They have special characteristics that help them get around in the dark. Most nocturnal animals have special eye adaptations. Human eyes adjust to the dark, but not as well as nocturnal animals. Bats have a special sonar-like system to help them know where they are. They send a signal out in front of them. This signal will go forward and hit something, then come back. The bat can tell how far away the object is and what it was by analyzing the rebounded signal. This is called echolocation.
1. Eyes - How do your eyes adjust in the dark? While the lights are on, look at your partner's eyes, or at your own in a mirror. Notice the size of the pupil. Now turn the lights so that they are off or very dim. Wait for a minute or two until your eyes have adjusted to the dark so that you can see your friend's eyes. Look at the size of the pupil now. Has it changed? Why do you think this is so?
2. Sonar - Take a ball and bounce it lightly at a hard wall in front of you about 2 feet away. Notice how it bounces back. Now take two steps back and try throwing it again, with the same amount of force. Did it come back faster or slower than before? Try taking two more steps back. Bounce the ball against the same wall again. What do you observe? What would happen if there was no wall in front of you?
1. What else might animals do to adapt to being awake at night?
2. Before you look up the answer, what do you think "diurnal" or "crepuscular" might mean?
Search in a dictionary, an encyclopedia, or on the ThinkQuest 25553 team's website to find what Diurnal and Crepuscular animals are. Find examples of at least two of each of these.
To have fun, follow up with Animals and Sleep Crossword Puzzles to extend your learning, located on ThinkQuest team 25553's website: Sleep: from A to Zzz! Some of them are especially devoted to Nocturnal animals!
(1) Whayne, Suzanne Santco. Night creatures. New York, Simon & Schuster, 1993, p. 8.
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