Grade 9 Applied Science – Unit 1 Ecosystems
Energy in Ecosystems
Chapter 2.5 Pages 38-41
We have learned that all energy originates from the Sun as RADIANT ENERGY (…energy that travels through
empty space…) AND only a very, very small amount of this energy reaches the surface of the Earth and it absorbed
by living organisms.
All organisms need energy to grow, BUT many organisms CANNOT use directly the energy from the sun. Instead,
the Sun’s energy must be CONVERTED into a form that can be used. This form is CHEMICAL ENERGY.
Organisms that use the Sun’s energy to make their own food are called PRODUCERS. Plants are producers and the
conversion process is PHOTOSYNTHESIS.
Chemical Process of Photosynthesis
Carbon dioxide + water + light energy
Sugar + Oxygen
Organisms that obtain their energy by consuming (eating) other organisms (…or the products of other organisms…)
are called CONSUMERS. You are a consumer. The food contains stored energy. When you eat and digest the
food, the energy is released by a process called CELLULAR RESPIRATION
Chemical Process of Cellular Respiration
Sugar + Oxygen
Carbon dioxide + water + energy
NOTE: Cellular Respiration is not breathing. Cellular Respiration is a chemical process that occurs in the cells of
living things. Breathing is the process of taking air into the lungs to get oxygen into cells.
OBSERVING CARBON DIOXIDE IN CELLULAR RESPIRATION
All cells need a continuous supply of energy. When your lungs take in oxygen, your cells use the process of cellular
respiration to convert chemical energy into a form that can be used. The by-product is carbon dioxide.
Limewater turns cloudy when combined with carbon dioxide.
Materials
 Transparent cup
 Limewater
 Drinking straw
 Scissors
 5 cm X 5 cm cardboard
Methods
 Fill the cup 1/3 full of limewater
 Record the appearance of the limewater
 Cut a small opening into the cardboard just large enough to slip a straw through
 Slide the cardboard about halfway along the straw
 Place one end of the straw in the limewater with the cardboard just above the top of the cup
 Slowly breathe out a steady stream of air into the other end of the straw.
 Record any changes in the appearance of the limewater
 How did the experiment give you evidence that cellular respiration occurred? Explain.