Photoautotrophs or
Phototroph (
GkGreek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical...
: photo = light, auto = self, troph = nourishment) are
organismIn biology, an organism is any living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homeostasis as a stable whole...
s (usually plants) that carry out
photosynthesisPhotosynthesis is a process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of Bacteria, but not in Archaea...
to acquire energy.
EnergyIn physics, energy is a scalar physical quantity that describes the amount of work that can be performed by a force, an attribute of objects and systems that is subject to a conservation law...
from
sunlightLight is electromagnetic radiation, particularly radiation of a wavelength that is visible to the human eye ....
,
carbon dioxideCarbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state...
and
waterWater is an ubiquitous chemical substance that is composed of hydrogen and oxygen and is essential for all known forms of life.In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam. Water covers 71%...
are converted into organic materials to be used in
cellularThe cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of an organism that is classified as living, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos...
functions such as
biosynthesisBiosynthesis is an enzyme-catalyzed process in cells of living organisms by which substrates are converted to more complex products. The biosynthesis process often consists of several enzymatic steps in which the product of one step is used as substrate in the following step...
and
respirationCellular respiration is one of the key ways a cell gains useful energy. It is the set of the metabolic reactions and processes that take place in organisms' cells to convert biochemical energy from nutrients into adenosine triphosphate , and then release waste products...
. In an
ecologicalEcology is the interdisciplinary scientific study of the interactions between organisms and the interactions of these organisms with their environment....
context, they provide nutrition for all other forms of life (besides other autotrophs such as
chemotrophChemotrophs are organisms that obtain energy by the oxidation of electron donating molecules in their environments. These molecules can be organic or inorganic . The chemotroph designation is in contrast to phototrophs which utilize solar energy...
s). In terrestrial environments
plantPlants are living organisms belonging to the kingdom Plantae. They include familiar organisms such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The scientific study of plants, known as botany, has identified about 350,000 extant species of plants, defined as seed plants,...
s are the predominant variety, while aquatic environments include a range of phototrophic organisms such as
algaeAlgae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms. The largest and most complex marine forms are called seaweeds. They are photosynthetic, like plants, and "simple" because they lack the many distinct organs found in...
(e.g.
Photoautotrophs or
Phototroph (
GkGreek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical...
: photo = light, auto = self, troph = nourishment) are
organismIn biology, an organism is any living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homeostasis as a stable whole...
s (usually plants) that carry out
photosynthesisPhotosynthesis is a process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of Bacteria, but not in Archaea...
to acquire energy.
EnergyIn physics, energy is a scalar physical quantity that describes the amount of work that can be performed by a force, an attribute of objects and systems that is subject to a conservation law...
from
sunlightLight is electromagnetic radiation, particularly radiation of a wavelength that is visible to the human eye ....
,
carbon dioxideCarbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state...
and
waterWater is an ubiquitous chemical substance that is composed of hydrogen and oxygen and is essential for all known forms of life.In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam. Water covers 71%...
are converted into organic materials to be used in
cellularThe cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of an organism that is classified as living, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos...
functions such as
biosynthesisBiosynthesis is an enzyme-catalyzed process in cells of living organisms by which substrates are converted to more complex products. The biosynthesis process often consists of several enzymatic steps in which the product of one step is used as substrate in the following step...
and
respirationCellular respiration is one of the key ways a cell gains useful energy. It is the set of the metabolic reactions and processes that take place in organisms' cells to convert biochemical energy from nutrients into adenosine triphosphate , and then release waste products...
. In an
ecologicalEcology is the interdisciplinary scientific study of the interactions between organisms and the interactions of these organisms with their environment....
context, they provide nutrition for all other forms of life (besides other autotrophs such as
chemotrophChemotrophs are organisms that obtain energy by the oxidation of electron donating molecules in their environments. These molecules can be organic or inorganic . The chemotroph designation is in contrast to phototrophs which utilize solar energy...
s). In terrestrial environments
plantPlants are living organisms belonging to the kingdom Plantae. They include familiar organisms such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The scientific study of plants, known as botany, has identified about 350,000 extant species of plants, defined as seed plants,...
s are the predominant variety, while aquatic environments include a range of phototrophic organisms such as
algaeAlgae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms. The largest and most complex marine forms are called seaweeds. They are photosynthetic, like plants, and "simple" because they lack the many distinct organs found in...
(e.g.
kelp{Taxobox| name =Kelp| image = Kelp In Freycinet Tasmania.jpg| image_width = 300px| image_caption = Kelp on rocky beach in Freycinet, Tasmania| regnum = Chromalveolata| phylum = Heterokontophyta| classis = Phaeophyceae| ordo = Laminariales...
), other
protistProtists , are a diverse group of eukaryotic microorganisms. Historically, protists were treated as the kingdom Protista but this group is no longer recognized in modern taxonomy...
s (such as
euglenaEuglena is a genus of unicellular protists, of the class Euglenoidea of the phylum Euglenozoa . They are single-celled organisms. Currently, over 1000 species of Euglena have been described. Marin et al. revised the genus to include several species without chloroplasts, formerly classified as...
) and
bacteriaThe bacteria are a large group of unicellular microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
(such as
cyanobacteriaCyanobacteria, also known as blue-green algae, blue-green bacteria or Cyanophyta, is a phylum of bacteria that obtain their energy through photosynthesis. The name "cyanobacteria" comes from the color of the bacteria = blue)...
). One product of this process is
starchStarch or amylum is a polysaccharide carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds.Starch is produced by all green plants as an energy store and is a major food source for humans....
, which is a storage or reserve form of
carbonCarbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
, which can be used when light conditions are too poor to satisfy the immediate needs of the organism. Photosynthetic bacteria have a substance called
bacteriochlorophyllBacteriochlorophylls are photosynthetic pigments that occur in various phototrophic bacteria. They are related to chlorophylls, which are the primary pigments in plants, algae, and cyanobacteria. Groups that contain bacteriochlorophyll conduct photosynthesis, but do not produce oxygen. They use...
, live in lakes and pools, and use the hydrogen from
hydrogen sulfideHydrogen sulfide is the chemical compound with the formula H
2S. This colorless, toxic and flammable gas is partially responsible for the foul odor of rotten eggs and flatulence....
instead of from water, for the chemical process. (The bacteriochlorophyll pigment absorbs light in the extreme UV and infra-red parts of the spectrum which is outside the range used by normal
chlorophyllChlorophyll is a green pigment found in most plants, algae, and cyanobacteria. Its name is derived from the Greek χλωρός and φύλλον...
). Cyanobacteria live in fresh water, seas,
soilSoil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics. It is composed of particles of broken rock that have been altered by chemical and...
and
lichenLichens are composite organisms consisting of a symbiotic association of a fungus with a photosynthetic partner , usually either a green alga or cyanobacterium...
, and use a plant-like photosynthesis.
A
photolithotrophic autotroph is an autotrophic organism that uses light energy, and an inorganic electron source (eg. H
2O, H
2, H
2S), and
CO2Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state...
as its
carbonCarbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
source. Examples include plants.
The depth to which sunlight or artificial light can penetrate into water, so that photosynthesis may occur, is known as the phototrophic zone.
Flowchart
- Autotroph
An autotroph is an organism that produces complex organic compounds from simple inorganic molecules using energy from light or inorganic chemical reactions....
- Chemoautotroph
- Photoautotroph
- Heterotroph
A Heterotroph is an organism that uses organic carbon for growth. This contrasts with autotrophs, such as plants, which are able to directly use sources of energy, such as light to produce organic substrates from inorganic carbon dioxide.- Ecology :Heterotrophs are known as consumers in food...
- Chemoheterotroph
- Photoheterotroph
Photoheterotrophs are heterotrophic organisms that use light for energy, but cannot use carbon dioxide as their sole carbon source. Consequently, they use organic compounds from the environment to satisfy their carbon requirements. They use compounds such as carbohydrates, fatty acids and...