Science 7
Unit 2
Earth & Life History
Name: ______________________________
Date: ______________ Period: __________
Sec 6.1 Earth Has Been Home to Living Things for About 3.8 Billion Years
BIG IDEA Species develop and change over time.
Vocabulary
1. extinction ________________________________________________________________________
2. mass extinction ___________________________________________________________________
Fossils provide evidence of earlier life.
3. What is one kind of evidence that is used to learn about early life? ______________________________
More complex organisms developed over time.
4. Did the first organisms have one cell or more than one cell? ________________________________
Early Forms of Life
5. Draw and label a picture to show what life on Earth was like 3.8 billion years ago.
Multicellular Organisms
6. Structures in organisms that used oxygen well were ____________________. Scientists think that they
joined with prokaryotes to become the first ____________________. The first eukaryotes had
____________________ cell. These eukaryotes later evolved into the first ____________________
animals.
7. How do scientists think that mitochondria helped in the evolution of multicellular eukaryotes? List 3
possible steps.
A. ___________________________________________________________________
B. ___________________________________________________________________
C. ___________________________________________________________________
Life on Land
8. What organisms were probably the first life forms to successfully move
from water to land? __________________________________________________
the first plants?__________________________________________
the first animals? ________________________________________
Earth’s history includes mass extinctions.
8. Fill in the main idea and details chart for the main idea shown.
Main Idea
Earth’s history includes mass
extinctions.
Details
 Extinctions means __________________
_________________________________
 Mass extinctions involve ______________
numbers of species disappearing in a
_________________ time.
 Fossil records show at least ____________
mass extinctions during _______________
10. Although the fossil record shows a pattern of mass extinction, two of these extinctions are particularly
interesting. In the chart below, fill in the missing information to describe each mass extinction.
Mass Extinction
When Did It
Happen?
What Happened?
Permian
a.
b.
Cretaceous
c.
d.
Possible Cause
land masses
moved together,
changing the
climate and
conditions within
Earth’s waters
an asteroid
collided with Earth