Name: _________________________________ Date: ______________________ Period: _____

Freshmen Biology

Modeling Earth’s History Week #____ So far we have learned about inheritance and how our traits are passed on. But where and how were these traits passed on in the first place? Where did living things even come from? We will investigate these questions by creating Earth’s timeline and then analyzing how life began.

Directions: Order the events by writing a number in each box. 1 is the oldest, or first event to occur.

Algae

(Multicellular life)

Amphibians

Land Plants

Single-celled Eukaryotes

Rapid Growth of

Continents

Hominids

(Early Humans)

Bacteria (First life)

Birds

Flowering Plants

Animals with

Shells

Soft Bodied

Animals

Modern Humans

Formation of the

Earth

Dinosaurs

Directions: Read and annotate the passage below, paying attention to the major events from above.

Earth began about 4.6 billion (4,600,000,000) years ago. Scientists estimate this is the age of the Earth based on the oldest materials found on the planet. Earth’s early existence was a violent one, with a constant bombardment from meteorites. When this ended, the Earth’s surface cooled and solidified into a crust. There were no continents yet – just a global ocean. With erosion and sedimentation, large continents formed around 4.1 billion years ago. However the continents that we know and recognize today formed much later – 3.5 billion years later. After a turbulent beginning, somehow life began with the appearance of single celled prokaryotes (bacteria) about 3.8 billion years ago. These single-celled bacteria were able to survive in an incredibly harsh environment. As the environment changed, more complex cells, eukaryotes were able to evolve, around 2.7 billion years ago. After the appearance of eukaryotes, multicellular organisms like algae appeared 2.1 billion years ago. These relatively simple multicellular organisms became more and more complex over the next 1 billion years. The last billion years has shown a tremendous diversity of life. First, soft-bodied animals appeared 600 million (0.6 billion) years ago and animals with shells appeared 60 million (0.06 billion) years later. Land plants then appeared, around 0.47 billion years ago. After the arrival of land plants, amphibians evolved about 370 million (0.37 billion) years ago. The era of large dinosaurs began 225 million (0.225 billion) years ago with birds evolving 150 million years ago. Flowering plants appeared only 20 million years after birds. The ancestors to humans arrived relatively recently, only 2.5 million (0.0025 billion) years ago with modern humans arriving 200,000 years ago, or 0.0002 billion years ago.

Name: ________________________________ Date: _______________________ Period: _____

Freshmen Biology

Directions: Use the events from the previous page to complete a timeline of Earth’s history. Refer to the passage in order to determine the proper placement of each event. This will be a draft of a larger timeline that you will create in class.

Present

1 Bya

2 Bya

3 Bya

4 Bya

5 Bya