2.5: Energy Flow in Ecosystems pg. 38 Radiant Energy: energy that travels through empty space. Producer: an organism that makes its own energy-rich food using the Sun s energy. Photosynthesis: the process by which the Sun s energy is converted into chemical energy. Consumers: organisms that obtain their energy by consuming other organisms, or the products of other organisms. Cellular Respiration: the process by which sugar and oxygen are converted into carbon dioxide, water, and energy to provide energy for the cell. The Sun is the primary source of energy for the planet Earth. All living things are dependent on the Sun for life. The Source of Energy Sun light is called radiant energy, which has the ability to pass through space and reach Earth from the Sun. Radiant energy is invisible; UV rays, Infrared, Microwaves, Radio Waves, and visible; white light made up red, orange, yellow, green, blue, indigo, and violet light. White light spectrum is the only light that can be detected by our eyes.
Where Does the Energy Go? The light that reaches Earth, 70% is absorbed by land, atmosphere, and water, and is converted to thermal energy, in the form of heat. This thermal energy warms the atmosphere (temperature changes) and influences weather patterns, as well as supports the water cycle. Only a small amount of energy is actually used by living things on the planet. All living things require an input of energy to survive. Organisms get their energy from the food they eat other then plants. Organisms can not use radiant or thermal energy as a source of survival. Radiant is converted to chemical potential energy (carbohydrates glucose) by plants through a process called photosynthesis. This chemical energy can be stored in organisms to be used later. Figure 1: How the Sun s radiant energy is distributed.
Photosynthesis Plants are producers they can make their own food. They are found on the first trophic level in a feeding relationship. Plants can photosynthesis, where they use radiant energy, carbon dioxide, and water to produce glucose and oxygen. Plants are green because their cells contain chlorophyll, which is a pigment that can trap radiant energy. The radiant energy is used to produce glucose and release oxygen into the atmosphere. Sun light + carbon dioxide + water glucose + oxygen Cellular Respiration Consumers are organisms that must consume food to obtain energy for survival. They are found on the second, third, four, and etc. trophic levels of a food chain or web. The food you eat is used by your cells in a process called cellular respiration. The glucose in your food and oxygen you breathe is used to release energy for life functions. The products from this process are carbon dioxide and water. Glucose + oxygen carbon dioxide + water + energy Cellular respiration is not breathing, gas exchange, it is a cellular activity.
Complementary Processes Photosynthesis and cellular respiration involve the same chemicals, carbon dioxide, water, oxygen, glucose (sugar), but in a different order, and each processes involve energy. The reactions are opposites of each other and produce different products. Photosynthesis: Sun light + carbon dioxide + water glucose + oxygen Cellular Respiration: Glucose + oxygen carbon dioxide + water + energy These processes are needed to sustain life on Earth. Figure 5: Photosynthesis and cellular respiration are processes that depend on each other.
Check Your Learning: Questions 1 7, pg. 41 Wrap Up: - Green plants are producers. Plants use photosynthesis to produce food and store the Sun s energy as chemical energy. - Consumers obtain energy when they eat other organisms or the products of other organisms. - Plants and animals perform cellular respiration to release energy from food. - Photosynthesis and cellular respiration are complementary processes.