Download Scientific Theories and Laws in Biology

Scientific Theories and Laws
in Biology
Mrs. Dignan’s Science Class
There are 3 Theories and a Law that support
most of what we know about Biology.
 1. What is a Scientific Theory?


An explanation of something in nature that is
widely accepted and heavily supported by
experimental data. It has not yet been disproven.

2. What is a a Scientific Law?

A description of the way things work in our
universe. They are generally much shorter than
theories
The 1st Law of thermodynamics
Matter and energy
cannot be created or
destroyed.
 They can change
forms, though.
 4. Give an example
of a reaction where
matter changes forms
but DOES NOT lose
mass.

The 1st Law of thermodynamics

5. Describe the energy
transformations shown in
the picture at right.
The Atomic Theory
All matter is made of
atoms
 Atoms of one element
have unique
properties and are
identical
 Atoms of different
elements are
distinctly different
 Atoms can bond with
other atoms to form

compounds
The Atomic Theory
Atoms are made of smaller
particles (protons,
electrons, and neutrons)
 The protons and neutrons
have the most mass and
occupy the solid nucleus at
the center of the atom
 The electrons orbit around
the nucleus at distinct
energy levels

The Atomic Theory



4.
5.
Protons have a positive
charge
Neutrons have a neutral
charge
Electrons have a negative
charge
Draw the model of the
carbon atom in your
notebook
How many electrons are
there in the 1st Energy
Level?
The Atomic Theory
6. Draw a model of an
Oxygen atom in your
notebook.
7. Draw a model of a
Hydrogen atom in your
notebook.
Cell Theory


All living things are
made out of at least
one cell (some are
made of trillions).
All cells come from
other cells.
Cell Theory
Cells are able to copy
themselves
 Cells contain special
machines in them
called “organelles” that
carry out operations
within the cell.
 All cells contain DNA,
the instructions for
making more cells.

The Theory of Evolution
DNA changes over
time through random
mutations
 Some mutations are
helpful and are kept
 Living things change
over time
 Eventually living things
can become separate
species.

The Germ Theory of Disease
Validated by Luis
Pasteur in the 19th
century.
 All living things come
from other living things.
 All living things will die.
 Living organisms must
enter an closed system
in order to grow in it.
