Final answer:
Plants are autotrophs that use photosynthesis to convert sunlight, carbon dioxide, and water into glucose and oxygen. The energy produced through this process is passed along food chains and ultimately released as heat after organisms use it. Cellular respiration in organisms like humans allows them to use the energy stored in food, producing carbon dioxide and water as byproducts.
Step-by-step explanation:
What is Photosynthesis?
Plants, being producers or autotrophs, create their own food through a process called photosynthesis. This process involves plants taking in carbon dioxide from the air, water from the soil, and energy from sunlight. Within the chloroplasts of plant cells, these materials undergo a chemical reaction to produce glucose, a sugar molecule, and oxygen, which is released as a byproduct into the atmosphere. The glucose functions as an energy source for the plant, while the oxygen contributes to the air that many organisms, including humans, need to breathe.
Flow of Energy in Ecosystems
The energy harnessed by photosynthesis flows through ecosystems via food chains. It starts with plants, the primary producers, which are eaten by herbivores, then by predators, and so on. At each step, energy is transferred, but some is also lost as heat. The original source of this energy is the sun, which is transformed into chemical energy within glucose molecules during photosynthesis. The ultimate form of energy, after being used by organisms, is largely heat that dissipates into the environment.
Cellular Respiration
Conversely, organisms like humans obtain energy by eating food, which includes plants or other organisms that have eaten plants. The stored energy in food originates primarily from photosynthesis. Through a process known as cellular respiration, cells break down glucose to release the energy and produce ATP, which powers cellular processes. The breakdown of food into energy results in carbon dioxide and water as byproducts, mirroring the reactants taken in during the photosynthesis process.