Where does all the bear's energy come from?
Bears get their energy from their food. Brown bears eat a varied diet, from nuts and berries to fish and other animals. When bears eat a berry, they are obtaining energy that the plant originally captured from the sun. Even when the bear eats an animal, the energy in that animal ultimately came from eating a producer that captured the sun's energy.
Energy is the ability to do work. In organisms, this work can be physical work, like walking or jumping, or it can be the work used to carry out the chemical processes in their cells. Every biochemical reaction that occurs in an organism's cells needs energy. All organisms need a constant supply of energy to stay alive.
Some organisms can get the energy directly from the sun. Other organisms get their energy from other organisms. Through predator-prey relationships, the energy of one organism is passed on to another. Energy is constantly flowing through a community. With just a few exceptions, all life on Earth depends on the sun’s energy for survival.
The energy of the sun is first captured by producers (Figure below), organisms that can make their own food. Many producers make their own food through the process of photosynthesis. The "food" the producers make is the sugar, glucose. Producers make food for the rest of the ecosystem. As energy is not recycled, energy must consistently be captured by producers. This energy is then passed on to the organisms that eat the producers, and then to the organisms that eat those organisms, and so on.
Recall that the only required ingredients needed for photosynthesis are sunlight, carbon dioxide (CO2), and water (H2O). From these simple inorganic ingredients, photosynthetic organisms produce the carbohydrate glucose (C6H12O6), and other complex organic compounds. Essentially, these producers are changing the energy from the sunlight into a usable form of energy.
The survival of every ecosystem is dependent on the producers. Without producers capturing the energy from the sun and turning it into glucose, an ecosystem could not exist. On land, plants are the dominant producers. Phytoplankton, tiny photosynthetic organisms, are the most common producers in the oceans and lakes. Algae, which is the green layer you might see floating on a pond, are an example of phytoplankton.
There are also bacteria that use chemical processes to produce food. They get their energy from sources other than the sun, but they are still called producers. This process is known as chemosynthesis, and is common in ecosystems without sunlight, such as certain marine ecosystems.
Producers include plants (a), algae (b), and diatoms (c).
chemosynthesis: Process of using the energy in chemical compounds to make food; characteristic of producers in ecosystems without sunlight.
energy: Ability to do work.
glucose: Simple sugar molecule with the chemical formula C6H12O6.
photosynthesis: Process by which specific organisms (including all plants) use the sun's energy to make their own food from carbon dioxide and water; process that converts the energy of the sun, or solar energy, into carbohydrates, a type of chemical energy.
phytoplankton: Tiny photosynthetic organisms that are producers in aquatic ecosystems.
predator-prey relationship: Interaction between two organisms of unlike species; one organism acts as predator that captures and feeds on the other organism, which serves as the prey.
producer: Organism that produces food (glucose) for itself and other organisms.
- With just a few exceptions, all life on Earth depends on the sun’s energy for survival.
- Producers make food for the rest of the ecosystem through the process of photosynthesis, where the energy of the sun is used to convert carbon dioxide and water into glucose.
Use the resource below to answer the questions that follow.
- Can producers function without sunlight? Why or why not? Explain your answer fully.
- What are some examples of producers? Why are they called autotrophs?
- How do some producers use sunlight to make "food"? What other resources do they require?
- Where does all the energy in an ecosystem ultimately come from?
- What "ingredients" are needed for the process of photosynthesis?