Science Re-Focus Lesson
Grade: 8
Goal/Objective(s): 5.01
Directions:
The teacher will begin the lesson by leading the class through an age comparison activity (see Teacher Guide). The teacher will put five pictures of different people on the board. The students will be asked to put them in order from youngest to oldest, using only the information they can gather from the pictures. The teacher will ask questions about how the students arrived at their conclusions (babies suck on pacifiers, adolescent kids have braces, older people have grey hair, etc.). She will then ask what information would help them know conclusively how to organize the people from oldest to youngest (birth certificates).
The teacher will then write the key terms for today’s lesson on the board (absolute age, radiometric dating, relative age, index fossil, unconformity and Law of Superposition). If the students already know the meaning of any of the terms, they can be discussed as a class.
The students will then silently read the outline on the Student Handout. They will circle or highlight key terms as they read. When they have finished, the teacher will re-read the outline out loud, and review the meaning of the bold-faced terms.
The students will then complete the open compare and contrast graphic organizer. They may work independently or in pairs. The teacher will review the correct answers to the graphic organizer when the students have finished.
Extension: The students will complete a “Graffiti Walls” activity (see Teacher Guide).
Essential learning(s):
1) How do index fossils help us understand life forms in the four major geologic eras? 2) How can unconformity be used as evidence of geologic evolution?
3) What is the Law of Superposition?
4) How is the age of the earth determined?
Attachments included:
Student Handout Teacher GuideEquipment/Supplies
needed:
Pencil Tape Large paper MarkersAssessment Directions:
The teacher will draw a “Window Note” on the board (see Teacher Guide). The students will copy it onto a sheet of paper and fill it in. The teacher will collect it at the end of class.Absolute Age vs. Relative Age – Teacher Guide
Age Comparison Activity:
Outline:
I. Have you ever wondered how scientists know the age of rocks and fossils?
a. There are two general techniques they use: by finding the absolute age and the relative age. II. Absolute age – the exact age of rocks and fossils
a. Gives scientists a good idea of the exact age of the rock or fossil b. How is it done?
i. By using radiometric dating
ii. Radiometric dating – measures the age of rocks and fossils based on the decay of certain isotopes they contain
iii. Example: A plant dies 200 million years ago and is covered in sediment. The amount of carbon-14 (an isotope found in all living things) in the plant begins to decay at a constant rate as soon as the plant dies. By looking at the amount of carbon-14 in the plant fossil, scientists can determine its age.
III. Relative age – the general age of rocks and fossils, as compared to the age of other rocks and fossils
a. Gives scientists a way to compare the ages of rocks and fossils. b. How is it done?
i. By using several different methods:
1. The Law of Superposition – states that in undisturbed rock, older rock layers are found below younger rock layers.
2. Index fossils – fossils of organisms that lived for a short time in Earth’s history.
a. Example – Trilobites lived 540 million years ago. If scientists are studying a layer of rock and come across a trilobite fossil, they know the age of that layer of rock.
3. Unconformity – when one layer of rock (or more) is missing because of erosion. a. Example – When looking at a cross section of rock, sometimes there
are places where parts of rock layers are missing. This tells scientists that there are parts of the history of that area that has been
Directions: Fill in the comparison chart below.
Conclusions –
The process of finding the absolute and relative ages of rocks and fossils are different, but they both help scientists understand more about Earth’s history.How are they
different?
1) Relative age is less exact
2) Uses the Law of Superposition, unconformities and index fossils
3)
Finding relative age is not necessarily a technical process 1) Absolute age ismore exact 2) Uses radiometric
dating
3) Finding absolute age is a more technical process
How are they alike?
1)
They are both ways to date fossils and rocks
Extension: Graffiti Walls Activity
Each student will be given one large sheet of paper, a large strip of tape and some markers. The students will move to an area in the classroom that has open wall space and tape their sheet of paper to it. The teacher will give each student one of the terms from today’s lesson and tell them to draw a picture of it on their paper. The students will only have about five minutes to do this. When they have finished, the teacher will ask each student to explain their drawing to the class. Even students who got the same terms should have a different drawing for that term.
Assessment: Window Note
The teacher will draw the following graphic organizer on the board. The students will fill it in and turn it in to the teacher before the end of class.
Facts: 1) 2)
Feelings: 1) 2)
Questions: 1) 2)
Ideas: 1) 2)
