The Importance of Plants

1
The Importance of Plants
Chapter 1 Lesson 3
2

• In this lesson you will learn how plants make
  food.

3
Photosynthesis

• All living things need energy to survive.
• A plant gets this energy from light, especially
  sunlight.
• Light is a form of energy that plants use to make
  their food.
• The food-making process that uses sunlight is
  called photosynthesis.

4
Photosynthesis

• Sunlight strikes the green part of a plant, such
  as a leaf.
• The leaf contains a green chemical called
  chlorophyll, which helps the plant make its food.
• Inside the leaf, water and carbon dioxide from
  the air combine to make sugar and oxygen.
• This reaction could not take place without the
  help of light energy.

5
Photosynthesis

• The sugar produced by the Sun's energy goes to
  all parts of the plant.
• The oxygen produced by the plant goes into the
  air.
• Animals must breathe oxygen to stay alive.
• At the same time, animals breathe out carbon
  dioxide, which plants need.

6
Changing Leaves

• Leaves of all plants, except evergreens, appear
  to change color in the fall.
• Actually, all the yellows and oranges you see in
  fall have been present in the leaves since
  summer.
• However, you could not see them because of the
  large amount of green chlorophyll inside the
  leaves.
• As the temperature begins to drop, the leaves of
  trees other than evergreens stop making
  chlorophyll.
• Slowly the chlorophyll that remains begins to
  break down and vanish.
• Now you can see the yellow and orange colors.
• If the weather is especially cool and the sky is
  clear most of the time, the color red will appear
  in leaves.
• This extra color was not in the leaves to begin
  withit is made only by leaves in places where
  the climate is cool and clear.

7

• A plant must efficiently move water from its
  roots to all its parts.
• The cells of every part of a plant need water to
  carry out vital chemical reactions, including
  photosynthesis.
• Water also helps plants stay firm.
• Plants constantly lose water through
  transpiration.

8
The Importance of Plants

• Whether you know it or not, you have probably
  eaten all parts of a plant roots, stems, leaves,
  seeds, fruit, and even bark and sap.
• Plants are the food and oxygen producers. They
  provide the food we eat and the oxygen we
  breathe.
• Plants and animals need each other in order to
  survive.
• Animals need the food and oxygen plants make
  during photosynthesis.
• Plants need the carbon dioxide animals give off
  when they breathe out.