7th or 8th Grade Integrated Science
Standard III: Objective 3
Title: Layers of Change
Description: Students match horse fossils to their time periods and pictures to emphasize, the
concept that more recent rock layers are more likely to contain fossils that are similar to existing
species than are older layers.
Materials Needed: Student sheet, envelopes containing a set of pictures, dates and horse leg fossils
(printed below) all items need to be cut away from one another.
Time Needed: 50 minutes
Background knowledge: Students should already be familiar with the law of superposition and
have an understanding that the fossil record shows that organisms have changed over time.
Teacher Procedures:
1. Hook activity – show a youtube video like: http://www.youtube.com/watch?v=tNpHDt5-fvU
Discuss how modern horses are bred to perform different tasks and that they look different from their
primitive ancestors
2. Read the introduction on the student sheet with the students.
3. Explain the procedures to students to match their pictures and dates.
5. When the students have shown you their work, have them fill in their data table and answer the
analysis questions.
Scoring Rubric or answer key:
1. Foldable neat, followed all directions.......……………………….4
2. Answered questions correctly……………….…..………………..4
3. Conclusion displays learning goal………………………………..4
Analysis question answers:
1. Horses are bigger, have a central toe that is larger than the others and have changed in shape.
2. An individual horse did not change but may have been more successful and had more offspring
with the successful traits.
3. Animals in the top layers are more recent ancestors.
4. The hoof may be more successful on rough or hard ground.
5. More abundant food or better success moving to it.
6. A variety of answers are possible, faster, jump higher, look pretty, good temperament.
55 MYA
12 MYA
25 MYA
35 MYA
Recent
Student Page
Name____________________
Title: Horse Fossils
Introduction: By studying fossils, paleontologists can see how species have changed over time. As
you look at the fossils in older and older rock layers, the fossils usually look less and less like today’s
organisms. Organisms found in the oldest rocks look the most different from today’s life forms.
In this activity you will analyze the fossil record of the horse. Horse fossils are common and
show clear changes over time. Keep in mind that the fossil record show very slow changes,
measured in millions of years. No single individual horse changed, rather, populations change as
offspring best suited to their environment are able to survive and pass their traits on to their offspring.
Remember the 7th grade adaptations and genetic unit?
Procedures:
1. Cut out the horse fossils, pictures and date.
2. Match the dates, fossils and pictures for each horse and place them in the
right spot on your table.
3. Have your teacher check your work.
4. Tape them in place.
5. When you have finished, answer the analysis questions below.
Data:
Time
Recent
12 MYA
Leg Bones
Picture
25 MYA
35 MYA
55 MYA
Analysis
1.) What are three ways the horse has changed slowly over time?
Horses are bigger, have a central toe that is larger than the others and have changed in shape.
2.) Did an individual horse change? Why?
An individual horse did not change but may have been more successful and had more
offspring with the successful traits.
3.) Why would the animals that lived 20 million years ago look more like animals today than animals
that lived 100 million years ago? . Animals in the top layers are more recent ancestors.
4.) What might be the reason a large central toe (the hoof) would be a more successful model for
horses? The hoof may be more successful on rough or hard ground.
5.) What environmental factors may have changed to allow some horse ancestors become larger?
More abundant food or better success moving to it.
6.) What changes have humans selected for in modern horses?
A variety of answers are possible, faster, jump higher, look pretty, good temperament.
Conclusion:
Write a 30 word summary of what you learned from this activity. Use the Step-Up-To-Writing (green, yellow, red)
method to develop a thesis/topic sentence and label each sentence.