Organisms that make their own food are called autotrophs, a term meaning “self-feeding.” These are the producers at the base of every food chain on Earth, building energy-rich carbohydrate molecules from simple raw materials like water, carbon dioxide, and either sunlight or chemical compounds. Plants are the most familiar example, but the group also includes algae, many bacteria, and some single-celled organisms in the deep ocean that never see a ray of light.
How Photosynthesis Works
The vast majority of food-making organisms rely on photosynthesis. The basic recipe is straightforward: water plus carbon dioxide, powered by sunlight, produces sugar and releases oxygen as a byproduct. This reaction happens inside tiny structures called chloroplasts, which contain the green pigment chlorophyll. When a photon of sunlight hits a chlorophyll molecule, it bumps an electron into a higher energy state, kicking off a chain of chemical reactions that ultimately store that solar energy in the bonds of sugar molecules.
The process has two main stages. In the light-dependent reactions, chlorophyll absorbs sunlight and splits water molecules apart, releasing oxygen into the air and generating two energy-carrying molecules. In the second stage, sometimes called the carbon-fixation cycle, those energy carriers power the conversion of carbon dioxide into carbohydrates. The plant then uses those carbohydrates as fuel for growth, reproduction, and every other life process.
Photosynthetic efficiency is surprisingly low. Typical plants convert only about 3% to 6% of the solar energy they receive into usable biomass, and the theoretical maximum tops out around 11%. Algae tend to outperform land plants in this regard, growing faster and capturing atmospheric carbon more efficiently per unit of surface area.
Chemosynthesis: Making Food Without Sunlight
Not all autotrophs need light. Deep on the ocean floor, near hydrothermal vents where superheated water gushes from cracks in the Earth’s crust, bacteria build organic molecules through chemosynthesis. Instead of capturing photons, these microbes harvest energy from chemical compounds like hydrogen sulfide and hydrogen gas rising out of the vents. They combine that chemical energy with oxygen or nitrate from the surrounding seawater to convert carbon dioxide into the biological building blocks of life.
These vent communities support entire ecosystems in total darkness, including giant tube worms, clams, and shrimp that depend on chemosynthetic bacteria for nutrition. It’s a vivid reminder that sunlight isn’t the only energy source capable of fueling life.
Which Organisms Are Autotrophs
The list is broader than most people realize. Land plants, from towering redwoods to lawn grass, are the most visible autotrophs. But marine organisms contribute an enormous share of global food production. Roughly half of all oxygen produced on Earth comes from the ocean, generated by photosynthetic plankton, algae, and cyanobacteria floating near the surface. One species in particular, Prochlorococcus, is the smallest photosynthetic organism on the planet, yet it alone produces up to 20% of the oxygen in the entire biosphere. That’s more than all the tropical rainforests combined.
Cyanobacteria deserve special mention. They are the only bacteria that perform oxygen-releasing photosynthesis, and they fundamentally shaped the planet. Around 2.4 billion years ago, cyanobacteria triggered the Great Oxidation Event, flooding Earth’s atmosphere with oxygen for the first time and making complex animal life possible. Their fossil record stretches back at least 1.9 billion years, making them among the oldest identifiable life forms preserved in rock.
Organisms That Blur the Line
Biology rarely draws clean boundaries, and food-making is no exception. Carnivorous plants like the Venus flytrap, sundews, and bladderworts photosynthesize like any other plant, but they also digest insects and absorb carbon from their prey. Research has shown that the Venus flytrap uses prey-derived carbon to fuel respiration in the trap that caught the insect, while sundews and butterworts actually move that carbon to other parts of the plant. Some aquatic bladderworts can even grow in complete darkness if given a carbohydrate-rich medium. Because these plants combine self-made food with nutrients absorbed from other organisms, scientists increasingly describe them as mixotrophs rather than pure autotrophs.
On the opposite end of the spectrum, some plants have completely lost the ability to make their own food. Ghost plant (Monotropa uniflora), a pale, waxy wildflower with no chlorophyll at all, gets its nutrition by tapping into underground fungal networks connected to the roots of nearby trees. Other examples include snow plant, coralroot orchids, and broomrapes. These plants are heterotrophs, fully dependent on other organisms for their carbon and energy, even though they’re still technically plants.
Why Autotrophs Matter to Every Living Thing
Every animal, fungus, and non-photosynthetic microbe on Earth depends, directly or indirectly, on organisms that make their own food. Autotrophs capture energy from the sun or from chemicals and lock it into organic molecules. Herbivores eat those molecules. Predators eat the herbivores. Decomposers break down whatever’s left. Remove the autotrophs and the entire system collapses.
This role is why ecologists call autotrophs “producers.” They don’t just feed themselves. They produce the chemical energy that flows through every food web on the planet, from a backyard garden to the deep-sea vent fields thousands of meters below the ocean surface.
Artificial Photosynthesis
Scientists are now trying to replicate what autotrophs do naturally. In 2025, researchers at Lawrence Berkeley National Laboratory unveiled an artificial leaf about the size of a postage stamp that converts carbon dioxide into useful chemical products using only sunlight. The device uses a light-absorbing material called perovskite to mimic chlorophyll and tiny copper structures to mimic the enzymes that regulate natural photosynthesis. It represents over 20 years of research and is part of a larger Department of Energy initiative called the Liquid Sunlight Alliance. The next steps involve scaling up the device and improving its efficiency, but the core achievement is real: a fully self-contained system that turns CO₂ and sunlight into carbon-based molecules, just like a leaf.