Autotrophs in ecology are organisms that produce or manufacture their food and these include plants, algae, and cyanobacteria which are some of the autotrophs examples. Almost all autotrophs get their energy from the sun (light) or from inorganic substances (chemical).
Table of Contents
Autotrophs meaning
Autotrophs are also known as primary producers. They are organisms that have the ability to create their own food from organic compounds from light energy or chemical energy (e.g. inorganic sources) through photosynthesis and chemosynthesis. Autotrophs can perform photosynthesis because they have chlorophyll which is a green pigment that helps them absorb light.
What are autotrophs?
These are organisms that can produce their own food. For the most part, this is accomplished through the use of light energy, water, and carbon dioxide. Rather than using solar energy, some biological entities will use chemical energy to produce their own food. Therefore, autotrophs make their own food using energy from sunlight or inorganic chemical reactions.
The term “autotroph” is derived from the basic terms “auto” and “troph,” which mean “self” and “food,” respectively.
Autotrophs are always referred to as primary producers because of their ability to produce their own food and thus occupy the bottom of the food chain.
In essence, they are the foundation of an ecosystem’s energy pyramid, providing the fuel that all heterotrophs (organisms that rely on others for food) require to survive. They also differ greatly from those found on land to those found in aquatic environments.
Autotrophic organisms are critical because, without them, no other kinds of life would be able to exist.
For instance, herbivorous animals and carnivorous animals that consume herbivores could not exist without plants that make sugars from carbon dioxide gas and sunlight through the process of photosynthesis.
How do autotrophs obtain energy?
Most autotrophs obtain energy through a process known as photosynthesis. Autotrophs use the sun’s energy to convert water from the soil and carbon dioxide from the air into glucose(a nutrient).
Autotrophs examples
- Plants
- Green algae
- Iron bacteria (Acidithiobacillus ferrooxidans)
- Cyanobacteria
- Phytoplankton
- Nitrosomonas
The above-listed are some examples of autotrophs which will be discussed below.
Plants
This is an autotroph example that ranges in size from microscopic species to massive redwoods that tower over the world. Surprisingly most plants are multicellular eukaryotic autotrophs and these diverse species all use the same photosynthetic mechanism known as photosynthesis which takes place in chloroplasts.
These chloroplasts are specialized organelles that contain pigments like chlorophyll.
This pigment (chlorophyll) is commonly found in light-harvesting complexes, which are a scaffold of membrane-bound proteins.
The process of food production in plants starts when the pigment loses an electron as a result of light-driven oxidation and the high-energy electron then joins an electron transport chain, where it loses energy as it moves from one protein to the next, accompanied by oxidation and reduction reactions.
During the whole process, a proton gradient across the membrane is also fueled by the transit of a charged particle along the electron transport chain.
Together, the proton gradient and the electron transport chain fuel the synthesis of Adenosine Triphosphate, the cell’s energy currency (ATP). When animals feed on plants, they are able to use the energy (ATP) and organic components produced by the plants for their own purposes.
Green algae
Another example of autotrophs is the green algae, which you may recognize as pond scum. The green algae are a broad, loosely defined group of algae that includes the Chlorophyta and Charophyta/Streptophyta, which are now divided into separate divisions, as well as the more primitive Mesostigmatophyceae, Chlorokybophyceae, and Spirotaenia.
The green algae is an example of autotrophs in the tropical rainforest because they produce their own food through photosynthesis.
Iron bacteria (Acidithiobacillus ferrooxidans)
Acidithiobacillus ferrooxidans is a bacteria that gets its energy from ferrous iron. It does this by converting iron atoms from a molecule state that can’t be dissolved in water to a molecular one that can. Hence, it is a chemosynthetic autotroph.
Cyanobacteria
Another good autotroph example is the photosynthesizing prokaryotes known as cyanobacteria that have a fossil record dating back over three billion years.
They are among the first life forms to have appeared on Earth. Over the course of two billion years, they also contributed to the creation of an oxygen-rich atmosphere, opening the path for the types of life forms we see today.
They were previously categorized as algae because of their photosynthetic activity, and the name ‘blue-green algae’ is still used informally to refer to these prokaryotes.
Cyanobacteria as an autotroph example are thought to have evolved into modern-day chloroplasts and inside their structure, membrane protein complexes are also found in the cell membranes of these prokaryotes. Some of these membranes create cylindrical thylakoid sheets, which are similar to chloroplasts’ internal structure.
The cyanobacteria are essential for the health and survival of marine ecosystems because they play an important role in the creation of bioavailable carbon and nitrogen, and they are among the most important marine primary producers because they are consumed by organisms on the ocean floor, in shallow waters, and in open seas.
Phytoplankton
Phytoplankton is microscopic free-floating plants that carry out the majority of the ocean’s photosynthetic activity. They are the foundation of marine ecosystems and keep the ocean and oxygen levels in the atmosphere in check.
They are eaten by zooplankton, which are minute herbivorous animals that are devoured by organisms higher up in the food chain. Therefore, phytoplanktons are eukaryotic autotrophs that float near the surface of water and are the basis of the food chain.
Phytoplankton’s arrival is thought to have aided a huge evolutionary boom 250 million years ago. Following a major extinction at the end of the Paleozoic era, more nutrients and less predation allowed these plants to thrive in the waters.
Their abundance and improved nutritional content also aided the proliferation of primary consumers such as zooplankton. Some populations diversified and adapted to new conditions as these groupings of organisms grew and colonized greater ocean tracts, resulting in an unprecedented increase in species variety in the oceans.
Nitrosomonas
Nitrosomonas is another autotroph example and it is a genus of nitrogen-fixing bacteria that convert molecular nitrogen into an organic form that plants in the soil can absorb. These are chemoautotrophs that use the energy produced by the chemical reaction to prepare food.
These organisms absorb nitrogen and convert it to nitrate, which is then incorporated into plants as amino acids. Thus, they obtain the energy required for amino acid preparation from the nitrogen fixation reaction.
Types of autotrophs
- Photoautotrophs
- Chemoautotrophs
The two main types of autotrophs are based on how they produce their food. These organisms live in various environments and generate energy through various mechanisms (and materials) as listed above.
Photoautotrophs
The autotrophs that utilize light as their energy source are called Photoautotrophs. They practice phototrophy which is defined as the use of light energy (from the sun) for photosynthesis. Light energy from the sun is used here to create food material (organic material) from carbon dioxide and water.
The majority of organisms that use this method to produce food have both chloroplasts (membrane-bound organelles) and a membrane-bound nucleus and they are, therefore, eukaryotic organisms. Examples of photoautotrophs are higher plants (maize plant, trees, and grass), euglena, green algae, and cyanobacteria. Cyanobacteria is the only prokaryote that uses phototrophy.
All photoautotrophs have chlorophyll (or other equivalent pigments that allow them to absorb light energy) that allow them to capture light energy.
Photoautotrophs and photosynthesis
Chlorophyll is found in all photoautotrophs, as previously stated even though some organisms, such as cyanobacteria, do not have a chloroplast that contains chlorophyll. Such organisms like the cyanobacteria have unbounded chlorophyll in place in their cell to capture light energy for photosynthesis.
Photosynthesis occurs in higher plants in the mesophyll layer of the leaf. The leaf contains chloroplasts and carbon dioxide, which is required for photosynthesis. This carbon dioxide enters the mesophyll layer via small openings on the leaves known as stomata.
Chemoautotrophs
Chemoautotrophs are organisms that get their energy from inorganic chemical reactions. They are commonly found in deep water environments with no sunlight. These organisms are also known as chemosynthetic autotrophs.
Many chemosynthetic autotrophs live near deep-sea volcanic vents, which generate enough heat to allow rapid metabolism.
Chemoautotrophs obtain their energy from volatile chemicals such as molecular hydrogen, hydrogen sulfide, elemental sulfur, ferrous iron, and ammonia. This makes them well-suited to living in environments that would be toxic to many other organisms, as well as in areas where there is no sunlight.
Chemoautotrophs are typically bacteria or archaebacteria because their metabolisms are inefficient enough to support multicellularity.
Chemosynthetic autotrophs are classified into two types namely chemoorganotrophs (which use organic molecules as a source of energy) and chemolithotrophs (which use inorganic molecules). We will concentrate on chemolithotrophs because they do not produce energy from organic molecules.
These organisms, also known as lithotrophs, include a variety of bacteria, such as nitrifying bacteria and bacteria found in deep-sea tubeworms. Even though these organisms live in environments with no sunlight, there is enough inorganic material for biosynthesis (biosynthesis is essentially the oxidation of inorganic material).
The cells of chemolithotrophs take in electron donors (like iron, elemental sulfur, and hydrogen sulfide) and oxidize them to produce energy.
For example, the oxidation of hydrogen sulfide generates electrons that are transported through the electron transport chain to be used in oxidative phosphorylation, which generates ATP energy. The chemical energy in the form of ATP is then used in biosynthesis to fix carbon and create organic compounds.
Autotrophs vs heterotrophs
In an attempt to compare and contrast autotrophs and heterotrophs or to show the difference between heterotrophs and autotrophs a table will be used as shown below.
The basis for Comparison between autotrophs and heterotrophs | Autotroph | Heterotroph |
Definition | An autotroph is a type of organism that can produce its own food by utilizing a variety of substances such as water, sunlight, air, and other chemicals. | A heterotroph is an organism that obtains its food from other organisms because it is unable to produce its own food. |
Source of energy | Autotrophs obtain their energy from either sunlight or chemical reactions. | In heterotrophs, autotrophs are their direct or indirect source of energy. |
Dependency | Autotrophs are self-sufficient and can generate their own food. | Heterotrophs are either directly or indirectly dependent on autotrophic organisms. |
Trophic level | Autotrophs occupy the lowest trophic level in the food chain. | Heterotrophs are classified as the second or third trophic level in the food chain. |
Solar energy | Some autotrophs can store solar energy. | Heterotrophs are incapable of storing or utilizing solar energy. |
Role | Autotrophs are producers. | Heterotrophs are consumers. |
Types | Photoautotrophs and chemoautotrophs are the two types of autotrophs. | The two types of heterotrophs are phytotoheterotrophs and chemoheterotrophs. |
Organisms | Plants, algae, and some bacteria are examples of autotrophic organisms. | Algae, animals, fungi, and some bacteria are examples of heterotrophs. |
Photosynthesis | Photosynthesis is the primary metabolic pathway for energy production in autotrophic organisms. | Heterotrophs do not engage in photosynthesis. |
Photosynthetic pigments | Photosynthetic pigments are commonly found. | There are no photosynthetic pigments. |
Carbon source | They obtain their carbon from inorganic carbon. | Heterotrophs obtain their carbon from organic carbon. |
External energy source | Autotrophs require a source of energy from outside the body, such as sunlight or chemical reactions. | Most heterotrophs do not require a separate source of energy. Although, photoheterotrophs may derive energy from sunlight. |
Availability | They produce food at a specific time. For instance, plants produce food during the day, whereas chemoautotrophs rely on chemical reactions. | Heterotrophs can find food almost at any time of day. |
Examples | Plants, algae, cyanobacteria | Humans, animals, fungi, and heterotrophic bacteria |
What is the difference between autotrophs and heterotrophs?
The mode of nutrition is the major factor used to compare heterotrophs with autotrophs. Autotrophs differ from heterotrophs in that only autotrophs manufacture or produce their own food from inorganic substances while heterotrophs do not produce their own food, but rely on autotrophic organisms for the needed nutrient to live, grow, reproduce and survive.
The picture chart below gives a pictorial view of the differences between autotrophs and heterotrophs with examples or in other words, it helps to distinguish between autotrophs and heterotrophs.
Functions of autotrophs
Autotrophs differ from heterotrophs because they manufacture their own food. Therefore, autotrophs are always the primary source of biomass and they are the first trophic level in every ecosystem forming the bottom occupants of all energy pyramids. They use energy from the sun or chemical reactions to fix inorganic carbon as carbohydrates.
Their role in carbon dioxide sequestration makes them critical for global weather patterns, ensuring optimal temperature and annual rainfall. As a byproduct of photosynthesis, oxygen is produced, which is consumed by all organisms in order to release the chemical energy stored in carbohydrates.
Lichens which are part of the autotrophs in the tropical rainforest play an important role in altering the abiotic environment to make it more habitable. Because they hasten weathering and increase organic matter deposition, resulting in the formation of soil.
Other tropical rainforest autotrophs examples include Orchids, Bamboo Trees, Rubber Trees, Ferns, Bromeliads, Banana Trees, etc.
Autotrophs, along with abiotic factors, play an important role in determining species diversity in a region. For instance, if plankton is the primary producer, filter-feeding herbivores will proliferate, followed by carnivores that can consume these organisms.
Regions with tall trees, on the other hand, will favor herbivores like giraffes that can reach the higher branches and will then favor predators that can hunt these fast animals. As a result, the primary producer serves as the foundation for the entire ecosystem in the biodiversity of species.
Autotrophs in different environments
- Autotrophs in aquatic ecosystems
- Auto trophs in terestrial ecosystems
Autotrophs in aquatic ecosystems
Plants such as seaweeds and grasses are primary producers in areas of shallow water where sunlight can reach the bottom. Whereas, in the region where sunlight cannot reach the bottom of the water, microscopic plant cells known as phytoplankton provide the majority of the food for aquatic life. In essence, these are eukaryotic autotrophs that float near the surface of the water and are the basis of the food chain.
The oceans account for roughly half of all photosynthesis. Here, phytoplankton absorbs carbon dioxide and water from their surroundings and uses solar energy to create carbohydrates. These organisms form the base of the food chain for the entire ocean population because they are the primary source of food for zooplankton.
Autotrophic organisms are also found in freshwater and shallow saltwater areas and they include phytoplankton like green algae, aquatic plants like seagrasses and seaweed, as well as larger rooted plants like cattails that grow on the water’s surface and provide not only food but also a shelter for larger aquatic life.
These autotrophic organisms or primary producers are fed upon by insects, fish, and amphibians, which are then eaten by members of the secondary consumers in the fresh and saltwater systems.
There are also parts of the aquatic systems where sunlight cannot reach like the ocean floor, where primary producers continue to thrive. In these parts, the autotrophic organisms that thrive here are known to be chemosynthetic.
Because microorganisms congregate in areas such as hydrothermal vents and cold seeps, they derive their energy from the metabolism of surrounding inorganic materials (chemicals), that seep up from the seafloor, rather than sunlight.
Autotrophs in terestrial ecosystems
In a terrestrial ecosystem, autotrophs live and grow in areas where nutrients (organic matter) are available because they cannot move. Here, autotrophic organisms extract nutrients from decomposed organic matter in the soil and convert them into food for themselves.
Autotrophic organisms in the terrestrial environment use photosynthesis, like their aquatic counterparts, to convert nutrients and organic materials from the soil into food sources for other plants and animals. These organisms live on or near the soil’s surface because they require sunlight to process nutrients.
Sunlight does not penetrate deep into caves like in the ocean floor. As a result, bacterial colonies in some limestone caves are chemoautotrophic, or “rock-eating.” These bacteria, like those found in the ocean depths, get their nutrition from nitrogen, sulfur, or iron compounds found in or on the surface of rocks carried there by water seeping through the porous surface.
The role of autotrophs in an ecosystem
Autotrophs are the primary producers in a food chain, and energy in most ecosystems must flow through autotrophs because they are at the bottom of the ecological pyramid.
They are self-feeding organisms, which means they do not require food from other organisms because they have their own biological machinery for producing food. Animals, which are not like autotrophic organisms, cannot produce their own food and thus rely on primary producers, either directly or indirectly.
Most autotrophs store energy in the form of carbohydrates, sugars, and starch, and this energy flows to other members of the food chain when they feed on them.
Autotrophs are always playing an important role in the ecosystem’s nutrient cycling. They autotrophically degrade compounds, converting them into simpler molecules or another form that is either released into the environment or stored in the organism.
In the carbon cycle, for example, their role is to use carbon from carbon dioxide molecules when creating carbon-containing sugar molecules (e.g. glucose, C6H12O6). They also serve as an oxygen source through transpiration, especially when they release oxygen into the environment.
FAQs
What is an autotroph?
In ecology, an autotroph is an organism that acts as the primary producer in a food chain. Autotrophs make their own food using energy from the sun or inorganic elements.
What is the autotrophs definition in biology?
Autotrophs are organisms that build complex organic compounds from simple carbon sources such as carbon dioxide and rely on light or inorganic chemical reactions for energy.
Do autotrophs need to carry out cellular respiration?
Yes, autotrophs need to carry out cellular respiration.
Are protists autotrophs?
Some protists are autotrophic and have chloroplasts, while others are heterotrophic and consume food through absorption or engulfment (phagocytosis)
What are some autotrophs examples?
Plants, algae, plankton, and bacteria are all examples of autotrophs.
Why are most autotrophs referred to as the producers of the biosphere?
Because all nonautotrophic organisms rely on them as their primary source of organic compounds.
What are the two methods of food production observed in autotrophs?
The 2 methods of food production observed in autotrophs are photoautotrophy and chemoautotrophy.
Are bacteria autotrophs or heterotrophs?
Bacteria are both autotrophic and heterotrophs. This is because there are some species of bacteria that synthesize their own food and other groups of bacteria that depend on already made food.
Are trees autotrophs?
Yes, trees are autotrophic because they manufacture their own foods.
Are mushrooms autotrophs?
Mushrooms are not autotrophs because they are heterotrophic.
Are animals autotrophs or heterotrophs?
Animals are heterotrophs because they cannot manufacture their food from inorganic matter like plants, rather, they depend on plants.
Are decomposers heterotrophs or autotrophs?
Decomposers are heterotrophic organisms that decompose and feed on the remains of dead organisms as well as other organic wastes such as feces. They release simple inorganic molecules into the environment as a result of this process.
Are algae autotrophs or heterotrophs?
Algae are autotrophic and not heterotrophic. They fall under the protists that are autotrophs that photosynthesize.
What is the energy autotrophs use to make food?
Most autotrophic organisms produce their food through a process known as photosynthesis. They use the sun’s energy to convert water from the soil and carbon dioxide from the air into glucose, a nutrient and most autotrophs store energy in the form of glucose, starch, and cellulose.
Are plants autotrophs or heterotrophs?
Plants are autotrophic, which means they can feed themselves.
Are archaea autotrophs or heterotrophs?
Archaea are autotrophs and not heterotrophs because they use chemical synthesis to manufacture or produce their own food. Hence, they are known as chemosynthetic autotrophs.
Plants are photosynthetic autotrophs what does it mean?
Plants are photosynthetic autotrophs means they can produce their own food using the process of photosynthesis.
What is the function of autotrophs in the carbon cycle?
In the carbon cycle, autotrophs use carbon dioxide from the atmosphere or bicarbonate ions from water to produce organic compounds such as glucose.
Are archaebacteria autotrophs or heterotrophs?
Archaebacteria can be heterotrophic, photoautotrophic, or chemoautotrophic because some species can obtain nutrition through absorption (heterotrophs), while others use chemosynthesis or photosynthesis.
Are all plants autotrophs?
Yes, all plants are autotrophs because they produce their own food either through the use of light or chemicals.
What do autotrophs do during photosynthesis?
Autotrophs convert energy during photosynthesis as they use the sun’s energy to convert water from the soil and carbon dioxide from the air into glucose, a nutrient.
What are some examples of autotrophs and heterotrophs?
Autotroph examples include plants, cyanobacteria, and algae. While heterotrophs examples include, animals, fungi, and humans.
Are humans autotrophs?
No, humans are not autotrophs because they depend on other sources like plants and animals for food.
Pandas eat bamboo for energy, what are pandas?
Pandas are heterotrophs and not autotrophs because they rely on bamboo for energy.
Important marine autotrophs that have silica incorporated into their cell walls are?
The important marine autotrophs that have silica incorporated into their cell walls are coccolithophorids.
What are some autotrophs in the tropical rainforest?
Canopy Trees, lianas, epiphytes, orchids, bromeliads, algae, moss, and fern.
What is the total biomass of photosynthetic autotrophs present in an ecosystem is known as?
The total biomass of photosynthetic autotrophs present in an ecosystem is known as the net primary productivity.
What are autotrophs and heterotrophs?
Autotrophs refer to organisms that are capable of making their own food from raw materials and energy, while heterotrophs are consumers of autotrophs.
What is the difference between heterotrophs and autotrophs?
Autotrophs and heterotrophs difference is based on how they obtain energy. Autotrophs differ from heterotrophs in that only autotrophs manufacture or produce their own food from inorganic substances while heterotrophs do not produce their own food, but rely on autotrophic organisms for the needed nutrient to live, grow, reproduce and survive.
Plants are photosynthetic autotrophs what does this mean?
Plants are photosynthetic autotrophs, which means they have the ability to produce their own food and do it through the process of photosynthesis.
What is the function of autotrophs in the carbon cycle
The function of autotrophs in the carbon cycle is to use carbon from carbon dioxide molecules when creating carbon-containing sugar molecules (e.g. glucose, C6H12O6). They also serve as an oxygen source through transpiration, especially when they release oxygen into the environment.
Which kingdom is composed of multicellular autotrophs?
Kingdom Plantae
Which protists are autotrophs that photosynthesize?
Autotrophic protists that use photosynthesis to make their own food are called algae. These include red, brown, and green algae, as well as diatoms, dinoflagellates, and euglena.
Which organisms are autotrophs?
Algae, plants, and some bacteria and fungi.
Which process is directly used by autotrophs to store energy in glucose?
The process used is called photosynthesis which stores light energy in the form of glucose.