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182 SCIPAD - BIG IDEAS - BOOK 2
THE BASIS OF HEREDITY
Building a Geological Timescale
You are going to make a ‘time line’ showing how life on Earth has changed over the past 4 600
million years. First, you will assemble the time line from all its different periods. Then you will work
out when particular types of animals and plants first appeared. You will also see when two ‘mass
extinctions’ killed off many species, including the dinosaurs. Because the later stages of evolution
occurred relatively recently, you will expand the second part of your time line, covering the last
542 million years.
Instructions
1 Carefully colour in and cut out the different geological periods (white), making sure you
do not cut off the tabs. The numbers on each tab indicates the number of millions of years
before the present.
2 Line up the major eras , which are shaded to help you identify them. Put tabs with the same
number on top of one another.
3. Start gluing from left - i.e. the “Precambrian” period should be the first to be glued and
the “Paleozoic” period should be glued so that its tab is on top the Precambrian’s 542 tab.
Don’t forget we are going forwards in time so ‘0’ will be on the right.
4600 542
Precambrian
542 251
Paleozoic
4600 542
Precambrian 542 251
Paleozoic
251 65
Mesozoic 0
65 Cenozoic
Triassic
251 200 200
146
Jurassic
Cretaceous
146
65
251 65
Mesozoic 0
65 Cenozoic
Triassic
251 200 200
146
Jurassic Cretaceous
146
65
4600 542
Precambrian 542
488
542
Cambrian
Trilobites
520
Bacteria
3800
Multicelluar organisms
1000
Single cells
1800
4600 542
Precambrian
Bacteria
3800
Multicelluar organisms
1000
Single cells
1800
488
542
Cambrian
Trilobites
520
4. Place the geological periods on top of the eras in the correct place according to their
age. Again, starting on the left-hand side, glue in the periods.
5. Once your time frame is complete, cut out the different organisms and the mass extinctions
on the next page. The numbers on the tabs show how long ago they first appeared. Decide
where they should be located on your time line. Glue them to the main time line.
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