Living things need to
acquire energy; this is
a characteristic of life.
Energy
What is Energy?
• The capacity to cause change
• The ability to do work
• The ability to rearrange matter
Law of Conservation of Energy
• Energy cannot be created or
destroyed
• Energy can be converted from
one form to another
Introduction to Energy
Energy is in two basic forms:
1. Potential energy - stored energy
i.e. car at top of hill, coiled spring, ball
ready to be dropped
2. Kinetic energy - energy in motion
i.e. car rolling, spring unwinding, ball
falling
Figure 5.2
Fuel rich in
chemical
energy
Energy conversion
Waste products
poor in chemical
energy
Heat
energy
Octane
(from gasoline)
Carbon dioxide
Combustion
Kinetic
energy of
movement
Oxygen
Energy conversion in a car
Water
Heat
energy
Glucose
(from food)
Oxygen
Cellular
respiration
Carbon dioxide
ATP
Energy for cellular work
Energy conversion in a cell
Water
Energy Flow
Origin of virtually all the energy on Earth is the Sun
1. How much sunlight
actually reaches the
Earth?
2. How much sunlight is
used to power Earth’s
physical processes?
3. How much sunlight
actually reaches
producers in the
biosphere?
From that little bit of light, we get over 170 billion tons of
organic matter each year
Flow of Energy
The flow of energy in ecosystems
occurs in one direction; energy does
not cycle.
Energy is eventually
released as heat
Energy is not created,
destroyed, or recycled
Sunlight
Incandescent Light
Fluorescent Light
Grow Light
Heat Lamp
Green Light
Questions
1. Compare potential and kinetic energy and give an example of each
2. Define energy
3. Even though the Law of Conservation of Energy says energy cannot be created or
destroyed, why do we talk about plants creating their own energy and animals
consuming or burning energy
4. Compare energy use in living things to energy use in a car
5. Virtually all the energy on Earth comes from the ______
6. Explain why there is no Energy Cycle
7. Why are leaves green and why do they change color in the fall?
8. Explain which light is best for growing plants
9. Many people complain that fluorescent lights give them headaches. Suggest why.
10. Some people think certain radiation is a health hazard. Other people disagree.
Why is there so much debate about this topic?
Questions
1. Compare potential and kinetic energy and give an example of each
Kinetic – Energy at work – Car rolling down hill, Motor Running
Potential – Stored energy – Car at top of hill, Battery, Food
2. Define energy
Ability to do work
3. Even though the Law of Conservation of Energy says energy cannot be created or
destroyed, why do we talk about plants creating their own energy and animals
consuming or burning energy
Plants convert sunlight energy into chemical energy. They are essentially
creating their own food. Animals eat plants and convert that chemical energy
into other forms as well.
Questions
4. Compare energy use in living things to energy use in a car
Both cars and living things burn fuel through a combustion reaction. All burning
is combustion. Fuel is different but still requires oxygen to burn. Through
combustion energy is released for doing work, waste energy is released as heat,
and water vapor and carbon dioxide are released as byproducts.
5. Virtually all the energy on Earth comes from the ______
Sun
6. Explain why there is no Energy Cycle
Energy does not cycle… it is a one way trip to the sun. Even the heat energy
which is released back into space does not return to the sun to create more
energy
Questions
7. Why are leaves green and why do they change color in the fall?
Leaves are green because we are seeing the light reflect off the chlorophyll in
the leaf. In the fall when the chlorophyll dries up we see the natural colors of
the leaves.
8. Explain which light is best for growing plants
Chlorophyll reflects green and yellow light which means it does not absorb
those colors. Blues and reds are the colors the leaf absorbs and uses to energize
photosynthesis.
Questions
9. Many people complain that fluorescent lights give them headaches. Suggest why.
When you look at the spectrum of fluorescent lights you see lots of missing
color from the rainbow. The spectrum is not a full spectrum which means the
light is not as natural as sunlight and strains our eyes and nerves.
10. Some people think certain radiation is a health hazard. Other people disagree.
Why is there so much debate about this topic?
We don’t know the answer yet. We know that some technology emits ionizing
radiation. Ionizing radiation causes cancer and mutations in DNA. However, it is
also an important part of photosynthesis. There is a lot we still don’t know
about radiation and its impacts on us.