Final answer:
Organisms such as plants (autotrophs) capture energy from sunlight and store it in chemical compounds through photosynthesis. Animals and humans (heterotrophs) then obtain energy by consuming autotrophs or other heterotrophs. This represents an essential energy cycle that sustains life on Earth.
Step-by-step explanation:
In order to stay alive, organisms need to carry out reactions that require energy. Autotrophs, like plants, get that energy by trapping and storing the energy from sunlight in energy-rich compounds like carbohydrates through a process known as photosynthesis. Heterotrophs, which include humans and animals, get their energy when they consume these autotrophs or other heterotrophs. Humans release the energy needed for growth, breathing, thinking, and even dreaming through the chemical reactions that occur when they metabolize or break down digested food.
Where do living organisms get this chemical energy? Directly or indirectly, the process of photosynthesis provides most of the energy required by living things on Earth. During photosynthesis, autotrophs convert solar energy into chemical energy, which is then used to build carbohydrate molecules. The energy stored in the bonds of these molecules is released when an organism breaks down food. Cells use this energy to perform work, such as movement, and to maintain life's processes.
Heterotrophs, including humans, rely on consuming other organisms to obtain the chemical energy necessary for life. This energy flow is fundamental to ecosystems and is illustrated by food-web diagrams. The intake and metabolism of nutrients are critical for organisms to build complex organic molecules, maintain organized states, and perform the many tasks required by life's processes.