L4 The History of Life on Earth

L4 The History of Life on Earth

At the end of this lesson, you should be able to describe the evolution of life on Earth over time, using the geologic time scale.

VOCABULARY

Multiple Choice

A ________ is a trace or imprint of a living thing that is preserved by geological processes.

• fossil

• fossil record

• extinction

• geological time scale

Multiple Choice

All the fossils that have been discovered worldwide make up the ______ ________.

• fossil

• fossil record

• extinction

• geological time scale

Multiple Choice

An _______ happens when every individual of a species dies.

• fossil

• fossil record

• extinction

• geologic time scale

Multiple Choice

The ___________ is the standard method used to divide Earth's long 4.6-billion-year natural history into manageable parts.

• fossil

• fossil record

• extinction

• geologic time scale

How do we learn about ancient life?

• Paleontologist look for clues to understand what happened in the past.

• A paleontologist is a scientist who studies the fossilized remains of all kinds of organisms.

• Fossils of single-celled organisms date as far back as 3.8 billion years.

• A fossil is a trace or imprint of a living thing that is preserved by geological processes.

• When an organism is trapped in mud or sediment, the resulting fossil becomes part of that sedimentary layer of rock.

What can we learn from fossils?

• How life forms have changed over time

• when extinction occurred

Fossil Record

• All the fossils that have been discovered worldwide make up the fossil record. The fossil record gives evidence of many of the different organisms that have lived during Earth's long history.

• Each fossil gives information about a single organism.

• But overall, it helps us to understand larger patterns of change.

Ways to describe the age of fossils

• Relative dating - determines whether a fossil was formed before or after another fossil

• Absolute dating - estimate the age of a fossil in years

Look at picture and observe Fossil A on Page 40.

Example:

• Relative Dating : Organism A lived more recently than organism B. OR Organism A is younger than Organism B.

• Absolute Dating : Organism A lived between 75 and 130 million years ago.

Open Ended

Look at the picture on page 40.

What does relative dating tell you about FOSSIL B?

Open Ended

Look at the picture on page 40.

What does absolute dating tell you about FOSSIL B?

How Life Forms Have Changed Over Time

• Over many generations, populations change.

• Fossils show the gradual change in limb structure.

• Other species have survived for a long time without much change.

Open Ended

What changes do you see in the limb structure of the three animals on page 41?

When Extinction Occurs

• An extinction happens when every individual of a species dies.

• A mass extinction happens when a large number of species go extinct during a relatively short amount of time.

• Gradual environmental changes and catastrophic events can cause mass extinctions.

Poll

How old is the Earth?

• 4.2 million years old

• 56.3 million years old

• 4.6 billion years old

• 7.3 billion years old

What is the geologic time scale?

• To keep track of Earth's long history, scientists have developed the geologic time scale.

• The geologic time scale is the standard method used to divide Earth's long 4.6-billion-year natural history into manageable parts.

• A tool to Earth's history.

Open Ended

When did the Paleozoic era begin and end?

A tool to Organize Earth's History

• Time intervals correspond to significant changes in Earth's history.

• Some are defined by mass extinctions or significant changes in the number of species

• Others are defined by major changes in the Earth's surface or climate.

• The largest divisions of the geologic time scale are eons.

Open Ended

How long do you think an eon is?

• Eons are divided into eras.

• Eras are characterized by the type of organism that dominated the Earth at the time.

• Each era began with a change in the type of organism that was most dominant.

• Eras are further divided into periods.

• Periods are divided into epochs.

Multiple Select

Which three periods make up the Mesozoic era?

• Triassic

• Jurassic

• Permian

• Cretaceous

Poll

During the Precambrian time, where did prokaryotes live?

• on land

• in the ocean

Multiple Select

What defined the Paleozoic era?

• Organism continued to live in water

• Life moved onto land

Multiple Choice

What defined the Mesozoic era?

• Monkeys dominated the Earth.

• Prokaryotes dominated the Earth.

• Dinosaurs dominated the Earth.

• Human beings dominated the Earth.

Multiple Choice

During which era did primates evolved?

• Precambrian time

• Paleozoic era

• Mesozoic era

• Cenozoic era