Chapter 14, Lesson 3, "Eras in the Geologic Time Scale"

Materials:

Objective:

Anticipatory Set:* Students will be shown a simple timeline and asked what it is. Students will next be shown a vertical timeline. Explain that these timelines are not what scientists normally use to track history of the world. Students will be shown a Geologic Time scale similar to the one in the book on page 348. Extra Geologic time Scale with Sedimentary Rocks. Ask, what makes this different than a timeline. Students will describe what it is. The teacher will explain that all Geologic time scales are not alike. Show a second that is a little more complicated. A third that is very comlicated that lists the year and the type of life alive at a particular time. And finally show a spirl representation of the geologic time scale.

Teacher Input:* Scientists estimate that 99 percent of all organisms that once existed are now extinct. There are periods in the fossil record where a big group of animals dissappear at the same time. Scientists use the big changes to divide the history of the world into Eras. Have the student list the Precambrian Era in there notes and then below it list five characteristics of the time period.

Here is a summary of the section: (Students should jot down 4-5 characteristics of each period)

Precambrian Era

  1. The longest time period, about 85% of the time Earth has existed.
  2. 4.6 billion years ago to 540 million years ago.
  3. Precambrian Rocks found are mostly igneous or metamorphic.
  4. Rocks form the foundations of continents and can be found in some mountain ranges or in areas of high erosion.
  5. Contains simple organisms like bacteria from 3.5 million years ago.
  6. Algae, fungi, and bacteria were probably alive during this period.

Paleozoic Era

  1. 540 million years ago to 245 million years ago
  2. Life in the oceans developed
  3. Fossils of trilobites, sponges, and shellfish have been found in Paleozoic rocks.
  4. Very first land plants and animals developed at this time.
  5. Land life progressed from spiders and scorpions to amphibians to insects then reptiles.
  6. Insects were huge and dragonflies had the wingspan of eagles.
  7. The Appalachin Mountains formed
  8. Much of the oil and coal we use today formed by dead organisms in shallow swamps. (Northern Alaska was a tropical swamp or shallow ocean regeion)
  9. The trilobite died out at the end of the period.

Mesozoic Era

  1. 245 million years ago to about 65 million years ago.
  2. Life on land flourished.
  3. Trees similar to palms and spruces were very common.
  4. Small mammals and birds appeared.
  5. Dinosaurs were the dominate life on land.
  6. Dinosaur diversity was similar to that alive today when you campare lifestyles, sizes and diets.
  7. Alaska was still much different than it is today.
  8. The era ended when the dinosaurs died out.

Cenozoic Era

  1. From 65 million years ago to the present.
  2. Landforms have changed in this period Alps, Himalayas form; Great Lakes carved by glaciers.
  3. Early in the cenozoic Alaska was still different than today.
  4. Mammals have flourished and dominate life on land.
  5. The numbers of birds, reptiles, fish, insects, and plants have all increased during this time.
  6. 30 million types of animals are alive at this time on earth. A quickly changing world is opening up places for new organisms to exist. Also these changes in environment causes about 100 kins of organisms to become extinct each day.

Guided Practice:* Have Students read the did you know on Pages 350 and 351. Show this geologic time clock1 or clock 2.

Independent Practice:* Students will complete the worksheet, "Eras in the Geologic Time Scale: Terms Review"

Check for Understanding:* Students will take the quiz on Lesson 3, "Eras in the Geologic Time Scale"

 

Duration:

30 minutes + 10-15 for Independent Practice (Could be longer if taken for homework).

Alaska Content Standards Addressed in this lesson: