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# Dinosaurs - Lesson 2: Extinction

BIG IDEAS:Life can cease to exist because the conditions on earth that support it change and no longer meet a life form's needs. Dinosaurs' needs were very great.

## Whole Group Activities

Materials
• Book: What Ever Happened to the Dinosaurs? by B. Most
• Measuring tape to measure at least 50 feet or a 50-foot paper chain
• Paint brushes, a jar with water, lap chalkboard or similar writing surface
• Sorting trays with numerals zero to five written on the appropriate tray
• Appendix A - Dinosaur
• Word tags: extinction; disappear; evidence; diplodocus; theory

### Encountering the Idea

Have you seen a real dinosaur? Do you know how many dinosaurs exist today? Yes, zero is the number that tells us how many dinosaurs are alive today. We will be working with the number zero in the Mathematics and Science Centers again.

Read the story, What Ever Happened to the Dinosaurs? After reading, ask the students if they think some of the author's ideas about dinosaurs could be true. Tell students that they will be writing their stories about extinction at the Writing Center.

### Exploring the Idea

In our first activity we will discover more about dinosaurs. Students complete Activity - Measure a Dinosaur! as shown below.

Materials
50 feet of string; scratch paper, cut and strung into a chain at least 50 feet long
Paper chains of various lengths (heights of several of the students) to compare to the dinosaur chain

Procedures
Children go outdoors, if weather permits, otherwise use a hallway.

1. Children hypothesize as to the size of dinosaurs.
2. They measure 50 feet on a sidewalk or a hallway with the string; make a 50-foot paper chain to represent the length of a dinosaur.
3. Students compare the chain to their own heights.
4. They estimate how much food a dinosaur like the one they measured would need to eat every day. If they compare their height to the height of the dinosaur, can they get a better estimate?

Discussion
When you measured the dinosaur's size and then your own, who was bigger? Who was smaller? If you put some of your chains together, were they all together longer or shorter than the dinosaur? How do you know? Yes, you put them side by side to compare.
At the Mathematics Center, the students, working in small groups or in pairs,

1. classify the dinosaur models by color, size, and shape, after describing them to their partners
2. count a given number of dinosaurs to place under the correct numeral written on the sorting trays
3. say how many dinosaurs are alive now and point to the numeral that tells that number, and continue sequencing the dinosaur shapes.

At the Library Center, the children continue to read and look at the new book that was read for this lesson. Tapes of the book are available for the children to listen to, as they "read" the new book.

### Getting the Idea

None of us has seen a dinosaur. If that is true, how do we know that they even existed? (Pause for student responses.) Yes, we may have never seen a dinosaur, but we have seen parts of dinosaurs that have survived over millions of years. These parts, which are mostly bones, that have survived suggest to us that such things as dinosaurs existed.

We know that many of the animals such as the dinosaurs living on earth at the time were very large. That means that they needed a lot of food, whether it was plant or animal food. How much food did you estimate that dinosaurs the size of the one we measured would eat every day? Yes, if we compare our size to theirs and then estimate how much food we eat every day, we can get an idea of how much more food they would need.

What would happen if the dinosaurs could not get enough food? Yes, they would die. What else did they need? Air and water. If any of these needs were not met, what would happen to the dinosaurs? Yes, they would die. What would happen if they had many natural enemies and could not protect themselves? Yes, their enemies would kill them.

Introduce the word "evidence"; show it on a word card. Tell the children that there is "evidence", such as that found in fossils, that makes us believe that dinosaurs existed many years ago even though we have never seen one alive.

We know how big or how small they were because we have measured their fossils. Tell the students that there are several theories about what happened to the dinosaurs. A theory is like a guess, but it is a guess based on information or on the evidence that is available. In our lesson we will study some of these theories.

Theories about the extinction of the dinosaurs suggest that:

1. maybe their eggs were eaten by the dinosaurs' natural enemies, or by other dinosaurs;
2. maybe the land moved and caused the weather to change; when the weather changed the plants living at that time were not able to thrive and produce the amount of food needed to feed the dinosaurs, and the dinosaurs could not continue;
3. maybe a large star caused an explosion of cosmic rays that killed them all; or,
4. maybe a storm of meteors caused clouds to block the sun, which again affected the plants because they could not produce the amounts of food the dinosaurs required.
All of these suggestions are possible. Scientists, however, still do not know for certain why the dinosaurs ceased to exist. What do you think? What is your theory?

### Organizing the Idea

1. Students illustrate and write about the size of the dinosaur they measured, and how it compares to their own height.
2. At the Writing Center, students dictate reasons (which the teacher writes on a chart) for why dinosaurs disappeared. Then the students write and illustrate their reasons for why the dinosaurs became extinct. They trace and write the word "extinct."
3. Students complete Activity - If I Were A Diplodocus. Students discuss what a diplodocus is and then write or tell about:
If I were as long as a diplodocus, I would live ________, sleep _______,
go out to eat _________, be careful of my _____ . (The students can add to these ideas.)

### Closure and Assessment

Complete the lesson with the recitation:

One Friendly Dinosaur
One friendly dinosaur wanted to play peek-a-boo.
She found another, then there were two.

Two friendly dinosaurs looked behind a tree.
They found another, then there were three.

Three friendly dinosaurs went to find some more.
They found another, and then there were four.

Four friendly dinosaurs in the water did dive.
They found another, and then there were five.

Five friendly dinosaurs played in the sun.
They all ran to hide; now there are none.

Oral Interviews

1. How many of you made the dinosaurs "disappear" at the Science Center? Let's count.
2. What expression did you use that means the same as "disappear"? (Become extinct.)
3. How many dinosaurs exist today?
4. Teacher: I am going to hold up my hand and show zero, one, two, three, four, or five fingers. As soon as I hold up my hand and you know how many fingers I have up, raise your hand and tell me the number.
5. How do we know that dinosaurs existed many years ago?
6. What do you think happened to the dinosaurs?

Performance Assessment
Assess students' participation in the activities and the level of completion of their individual work. For example, assess a student's own explanation for the disappearance of the dinosaurs and work on Activity - If I Were a Diplodocus.