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.