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 SC.6.N.2.2: Explain that scientific knowledge is
durable because it is open to change as new evidence
or interpretations are encountered.
 SC.7.N.3.1: Recognize and explain the difference
between theories and laws and give several examples
of scientific theories and the evidence that supports
Bell Ringer
1. During the nineteenth century, biologists knew that South
America and Africa contained similar fossils. These fossils led them
to believe that a temporary land bridge between South America and
Africa allowed ancient species to move between both continents. In
the twentieth century, evidence showed that South America and
Africa were once part of the same larger continent and that there
were no land bridges between them. How should biologists respond
to the new geological finding?
A. Biologists should reject the geological finding, because it is new.
B. Biologists should ask physicists what to do, because physics is a
more exact science.
C. Biologists should reject the belief in ancient species, because
there were no land bridges.
D. Biologists should update the history of life, because it should
include the new geological finding.
Bell Ringer
3. The validity of scientific theories and laws depends on evidence. Which of the following
statements of evidence supports a law rather than a theory?
Electrons orbit the nucleus of an atom within a certain radius.
DNA analysis reveals that a modern species is related to an extinct species.
Seafloor spreading occurs at a rate of three centimeters per year in the mid-Atlantic.
The amount of matter in a closed system is the same at the start of a reaction as at the
end of the reaction.
4. There are many important laws and theories in science. Which of the following is a law
of science?
A living thing is made of at least one cell.
An atom is made of electrons orbiting a nucleus.
Gravity will pull two objects toward each other.
Natural selection will change species to fit their environments.
Item Drop
Seafloor Spreading
• One demonstration supports a theory, while the other can be
describe by a law.
• Scientific laws are like legal laws.
• both describe events.
• Scientific theories are more like a legal case or defense.
• both are used to explain events
Law vs. Theory
A law summarizes what happens
 A theory (model) is an attempt to
explain why it happens.
Law of Universal Gravitation
Law of Superposition
Law of Conservation of Mass
Law of Conservation of Energy
 A scientific law is a statement
that describes what scientists
expect to happen every time
under a particular set of
conditions. For example, the
law of gravity states that all
objects in the universe attract
each other. Unlike a theory, a
scientific law describes an
observed pattern in nature
without attempting to explain
it. Both scientific theories and
scientific laws are developed
slowly through repeated
observation and
The Theory of Evolution
Cell Theory
Atomic Theory
Theory of Plate Tectonics
 Scientific knowledge changes as a result
of new evidence or new interpretations
of existing evidence. For example,
thousands of years went by with people
thinking the sun revolved around the
Earth. To them, it made sense with
information they had. The sun would
rise on one side of the sky, move across
the sky, and set on the opposite side.
 A scientific theory is a well-tested
explanation for a wide range of
observations or experimental results. A
scientific theory connects large sets of
related observations by one explanation.
Examples of scientific theories include
the atomic theory and the cell theory.
The atomic theory states that all
substances are made up of tiny particles
called atoms. The cell theory states that
cells are the basic units of structure and
function in living things.
LEFT Side- Theories and Laws
Fill in the table below focusing on the difference
between what makes something a theory or a law.
Theories and Laws
Brief Description
Law of Universal
All objects in the
Universe attract each
Theory of Plate
All tectonic plates
were once connected
in a super continent
(Pangea). Now they
are moving apart.
Law of Superposition
The oldest layer of
rocks is always at the
Atomic Theory
Everything is made
up of tiny particles
Law of Conservation of Mass cannot be
created or destroyed.
Why is it a theory or a law?
Because it has been proven to be true every
Because scientists have enough evidence to
support it. Example all continents fit
together like a puzzle and there are similar
Because it is something scientists expect to
be true every time!!!!
There has been a lot of experimentation
with a lot of supporting evidence.
It has been proven true.
Exit Ticket
 Identify several theories and laws. Describe why each
is a law or a theory.
 Explain the difference between a scientific theory and
a scientific law.
 Explain why theories may be modified, but rarely