The Young Scientist Program http://ysp.wustl.edu
Washington University School of Medicine
Rope of Life
Number of Volunteers : 1 volunteer for every 4 students
Amount of Set-up Time : 10 minutes
Amount of Running Time : 10-20 minutes
Just how old is the earth? Students learn to think in terms of evolutionary time scales by retracing key events in the history of our planet along the Rope of Life. A rope with lines on it marking millions of years is laid out around the room, and students place note cards along the rope to guess when they think particular events occurred, such as the appearance of land plants, and the appearance of mammals. Then students will be given a new set of cards with the actual dates of the events, and will place them in the correct order. As a group, we will discuss with the students which events they had originally guessed correctly and what they were surprised about.
Note : there is no student worksheet accompanying this activity. It is purely discussionbased.
Missouri Science Standards
EC.4.3.A.9-12.b. Evidence for the nature and rates of evolution can be found in anatomical and molecular characteristics of organisms and in the fossil record: Evaluate the evidence that supports the theory of biological evolution (e.g., fossil records, similarities between DNA and protein structures, similarities between developmental stages of organisms, homologous and vestigial structures).
1. Describe how the composition of life on Earth has changed over time
2. Understand that for the first billion years of Earth’s 4.54 billion-year history, there were no living organisms
3. Understand that there is feedback between Earth and the organisms living on it. For example: a. Microbial life (bacteria) on land increased the formation of soil, which in turn allowed for the evolution of land plants b. Photosynthetic life (plants) changed the atmosphere by producing oxygen, which in turn allowed for the evolution of animal life (animals need oxygen to breathe)
This activity takes around 30 minutes to complete.
-Long rope (with tape marking every 50 million years)
“Events” note cards (each has an evolutionary event, such as “land plants first appear” or “mammals first appear”)
“Dates” note cards (each has the evolutionary event AND its actual date)

The Young Scientist Program http://ysp.wustl.edu
Washington University School of Medicine
Rope of Life
Based on past experience running this activity, you can expect…
-many students will be surprised at how long it took for life to first appear on earth
-they might think dinosaurs existed right after the earth formed
-they might think humans have been around much longer than we have
-they are surprised that a lot of major life events are bunched up towards the present
This kit is to help students visualize the key events that took place over the history of our planet.
The earth is around 4.5 billion years old and has provided an environment for the evolution of single celled organisms to multicellular organisms. Evolution is not a process that moves in a certain direction but instead it is stochastic. It is hard for some students to comprehend that much time has taken place. The basic timeline that is presented below lists the dates of the events that will be given to the students. The two that are not on there are: Dinosaurs first appeared on earth around 230 million years ago, Recorded history began around 5,000 years ago.
http://www.bbc.co.uk/nature/history_of_the_earth http://en.wikipedia.org/wiki/Timeline_of_evolutionary_history_of_life#Basic_timeline

The Young Scientist Program http://ysp.wustl.edu
Washington University School of Medicine
Rope of Life
1. Lay out the rope around the perimeter of the classroom. Make it clear which end represents the present, and which end represents 4.54 billion years ago.
2. Hand each student one or more “Events” note cards. Ask them to place each card where they think it goes on the rope. (It doesn’t matter if they have no idea where the cards go—just tell them to guess.)
3. Then give students the “Dates” note cards and have students place them in the correct places along the rope.
4. As a group, discuss with the students which events they had originally guessed correctly and what they were surprised about.

The Young Scientist Program http://ysp.wustl.edu
Washington University School of Medicine
Rope of Life
Note card
Note card
Present
4.54 million years ago
Note card
Note card
Examples of questions you might ask the students:
1) What is the oldest form of life on Earth?
2) How long have humans been around on Earth? Compared to other organisms, is this very long?
3) Why do you think bacteria appeared before land plants?
4) Why do you think plants appeared before animals? Could animals have arisen without plants? Why or why not?
5) Do you think the composition of life on Earth stays the same over time? What do you expect will happen to life on Earth in the future?
1) What is the oldest form of life on Earth? Bacteria (prokaryotes first appeared 3.6 billion years ago).
2) How long have humans been around on Earth? Compared to other organisms, is this very long? Humans have only been around for 200,000 years. This is a very small amount of time.
3) Why do you think bacteria appeared before land plants? Bacteria on land increased the formation of soil, which in turn allowed for the evolution of land plants
4) What do you think plants appeared before animals? Could animals have arisen without plants? Why or why not? Plants changed the atmosphere by producing oxygen (through photosynthesis), which in turn allowed for the evolution of animal life. Animals could not have arisen without plants, because animals need oxygen to breathe (and there was not nearly enough oxygen in the atmosphere until plants evolved).
5) Do you think the composition of life on Earth stays the same over time? What do you expect will happen to life on Earth in the future? The composition of life on Earth is constantly changing. All expectations are for it to continue this way, because organisms continue to adapt to

The Young Scientist Program http://ysp.wustl.edu
Washington University School of Medicine
Rope of Life the changing biotic and abiotic environment (plus, there are always mutations in DNA, which also bring about change).