Visualizing Time in a Biological Context
(modified version of the TimeLine)
How long is a million years? How long is a billion years? The vast amount of time
that has passed since the origin of Earth is difficult for most people to imagine.
However, when events in time are considered in relationship to one another, the
concept of time is easier to grasp. A time line helps to place events in context
with one another so that the vast amounts of time involved in Earth’s history
can be understood more easily.
Objectives:
 Construct a small timeline
 Explore the relationships of time and various events
 Describe the geological and evolutionary events in terms of time
Vocabulary Terms: (Definitions taken from Holt Biology Book)
Hominids- Primates that walk upright on two legs, characterized by opposable
thumbs, no tail, longer lower limbs; examples include modern humans and
ancestors
Pangea- All Earth’s landmasses connected into one huge supercontinent
Evolution- a change in the characteristics of a population from one generation
to the next; gradual development of organisms
Procedure:
1. Make a time line of 25 centimeters along the length of a sheet of paper given.
Mark this line on the left end “5,000,000” and on the right end “Present”. Every
centimeter on this line will represent 200,000 years. Mark and Label every
centimeter to as a guide.
2. Transfer only the events that have occurred during the last 5 million years
onto the timeline.
3. On this timeline, make a drawing that represents each of the events on your
timeline.
4. Then using ALL the Events in Earth’s History, place them in order on the
Table provided.
EVENTS IN EARTH’S HISTORY
Earth’s formation – 4.5 billion years ago
Fossil evidence of organisms in the Genus, Homo - 2 million years ago
Art Drawn in caves – 30,000 years ago
Evolution of modern humans -100000 years ago
Humans on Moon – ~40 years ago
Hominid Fossil footprints- 3.75 million years ago
Domination of the landscape by ferns – 225 million years ago
Evolution of land plants – 500 million years ago
First life forms in fossil record – 3.5 billion years ago
Hominid Fossils – 3.3 million years ago
Use of stone tools by humans – 2.5 million years ago
Evolution of vertebrates – 500 million years ago
Beginning of agriculture – 30000 years ago
Invention of spears – 300000 years ago
Evolution of eukaryotic cells – 2 billion years ago
Colonization of Europe by hominids – 700000 years ago
Formation of Pangea- 225 million years ago
Continents reach present positions – 55 million years ago
Invention of writing – 5000 years ago
Breaking apart of Pangea – 200 million years ago
TABLE 1:
Major Events in Earth’s History
Oldest to Most Recent
Event
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
Time
1. Analyzing Information:
How long has life existed on Earth?
_______________________________________
How long did only unicellular life-forms exist?
_______________________________________
2. Summarizing Information: Identify the major developments in life-forms
that have occurred in the last 3.5 billion years.
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
3. Inferring Relationships:
Look at the Geologic Time Scale on page 421. Which time period and Era
occurred in the past 5 million years. Mark these on your timeline.
___________________________________________________________
___________________________________________________________
4. Justifying Conclusions:
Cyanobacteria, the first prokaryotes to appear, are thought to be responsible
for adding oxygen to the Earth’s atmosphere. Using your book and knowledge,
justify this conclusion.
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
5. Determine the amount of time, as a percentage of the time that life has
existed on Earth, that humans (Homo sapiens) have existed. ______________
6. Using section 17-3 of your textbook, Make a timeline of the different eras
and Periods that have been documented. Remember to label your time line
dates.