Overview of cycle between autotrophs and heterotrophs

A heterotroph (/ˈhɛtərɵtroʊf/; ἕτερος heteros = "another", "different" and τροφή trophe = "nutrition") is an organism that cannot fix carbon and uses organic carbon for growth.^[1] This contrasts with autotrophs, such as plants and algae, which can use energy from sunlight (photoautotrophs) or inorganic compounds (lithoautotrophs) to produce organic compounds such as carbohydrates, fats, and proteins from inorganic carbon dioxide. These reduced carbon compounds can be used as an energy source by the autotroph and provide the energy in food consumed by heterotrophs.

Types[link]

Heterotrophs can be divided into two broad classes: photoheterotrophs and chemoheterotrophs. Photoheterotrophs, including most purple bacteria and green bacteria, produce ATP from light and use organic compounds to build structures. They consume little or none of the energy produced during photosynthesis to reduce NADP⁺ to NADPH for use in the Calvin cycle, as they do not need to use the Calvin cycle if carbohydrates are available in their diets.^[2] Chemoheterotrophs produce ATP by oxidizing chemical substances. There are two types of chemoheterotrophs: chemoorganoheterotrophs and chemolithoheterotrophs.^[2][3][4][5]

Chemoorganoheterotrophs (or simply organotrophs) exploit reduced carbon compounds as energy sources, such as carbohydrates, fats, and proteins from plants and animals. Chemolithoheterotrophs (or lithotrophic heterotrophs) such as colorless sulfur bacteria (e.g., Beggiatoa and Thiobacillus) and sulfate-reducing bacteria utilize inorganic substances to produce ATP, including hydrogen sulfide, elemental sulfur, thiosulfate, and molecular hydrogen.^[2][6][7][8] They use organic compounds to build structures. They do not fix carbon dioxide and apparently do not have the Calvin cycle.^[2] Chemolithoheterotrophs can be distinguished from mixotrophs (or facultative chemolithotroph), which can utilize either carbon dioxide or organic carbon as the carbon source.^[6][4]

Heterotrophs, by consuming reduced carbon compounds, are able to use all the energy that they obtain from food for growth and reproduction, unlike autotrophs, which must use some of their energy for carbon fixation. Heterotrophs are unable to make their own food, however, and whether using organic or inorganic energy sources, they can die from a lack of food. This applies not only to animals and fungi but also to bacteria.^[2]

Flowchart to determine if a species is autotroph, heterotroph, or a subtype

Ecology[link]

Most heterotrophs are chemoorganoheterotrophs (or simply organotrophs) and utilize organic compounds both as a carbon source and an energy source. The term "heterotroph" very often refers to chemoorganoheterotrophs. Heterotrophs function as consumers in food chains: they obtain organic carbon by eating other heterotrophs or autotrophs. They break down complex organic compounds (e.g., carbohydrates, fats, and proteins) produced by autotrophs into simpler compounds (e.g., carbohydrates into glucose, fats into fatty acids and glycerol, and proteins into amino acids). They release energy by oxidizing carbon and hydrogen atoms present in carbohydrates, lipids, and proteins to carbon dioxide and water, respectively.

Most opisthokonts and prokaryotes are heterotrophic; in particular, all animals and fungi are heterotrophs.^[9] Some animals, such as corals, form symbiotic relationships with autotrophs and obtain organic carbon in this way. Furthermore, some parasitic plants have also turned fully or partially heterotrophic, while carnivorous plants consume animals to augment their nitrogen supply while remaining autotrophic.

See also[link]

• Primary nutritional groups
• Auxotrophy
• Saprotrophic nutrition

References[link]

v t e Feeding behaviours Carnivores adult Hematophagy Insectivore Lepidophagy Man-eater Molluscivore Mucophagy Myrmecophagy Ophiophagy Piscivore Avivore Spongivore Vermivore Herpetivore reproductive Oophagy Paedophagy Placentophagy Breastfeeding Weaning cannibalistic Cannibalism Human cannibalism Self-cannibalism Sexual cannibalism Herbivores Folivore Frugivore Graminivore Granivore Nectarivore Palynivore Xylophagy Osteophagy Cellular Phagocytosis Myzocytosis Others Bacterivore Fungivore Coprophagia Detritivore Geophagy Omnivore Methods Apex predator Bait balls Bottom feeding Browsing Feeding frenzy Filter feeding Grazing Hypercarnivore Intraguild predation Kleptoparasitism Scavenging Trophallaxis Predation Antipredator adaptation Carnivorous plant Carnivorous fungus Carnivorous protist Category:Eating behaviors

v t e Modelling ecosystems – trophic components General Abiotic component Abiotic stress Behaviour Biogeochemical cycle Biomass Biotic component Biotic stress Carrying capacity Competition Ecosystem Ecosystem ecology Ecosystem model Keystone species List of feeding behaviours Metabolic theory of ecology Productivity Producers Autotrophs Chemosynthesis Chemotrophs Foundation species Mixotrophs Myco-heterotrophy Mycotroph Organotrophs Photoheterotrophs Photosynthesis Photosynthetic efficiency Phototrophs Primary nutritional groups Primary production Consumers Apex predator Bacterivore Carnivores Chemoorganotroph Foraging Generalist and specialist species Intraguild predation Herbivores Heterotroph Heterotrophic nutrition Insectivore Mesopredator release hypothesis Omnivores Optimal foraging theory Predation Prey switching Decomposers Chemoorganoheterotrophy Decomposition Detritivores Detritus Microorganisms Archaea Bacteriophage Environmental microbiology Lithoautotroph Lithotrophy Microbial cooperation Microbial ecology Microbial food web Microbial intelligence Microbial loop Microbial mat Microbial metabolism Phage ecology Food webs Biomagnification Ecological efficiency Ecological pyramid Energy flow Food chain Trophic level Example webs Cold seeps Hydrothermal vents Intertidal Kelp forests Lakes North Pacific Subtropical Gyre Rivers San Francisco Estuary Soil Tidal pool Processes Ascendency Bioaccumulation Cascade effect Climax community Competitive exclusion principle Consumer-resource systems Copiotrophs Dominance Ecological network Ecological succession Energy quality Energy Systems Language f-ratio Feed conversion ratio Feeding frenzy Mesotrophic soil Nutrient cycle Oligotroph Paradox of the plankton Trophic cascade Trophic mutualism Trophic state index Defense/counter Animal coloration Antipredator adaptations Camouflage Herbivore adaptations to plant defense Mimicry Plant defense against herbivory Predator avoidance in schooling fish

v t e Modelling ecosystems – other components Population ecology Abundance Allee effect Depensation Ecological yield Effective population size Intraspecific competition Logistic function Malthusian growth model Maximum sustainable yield Overpopulation in wild animals Overexploitation Population cycle Population dynamics Population modeling Population size Predator–prey equations Recruitment Resilience Small population size Stability Species Biodiversity Density-dependent inhibition Ecological effects of biodiversity Ecological extinction Endemic species Flagship species Gradient analysis Indicator species Introduced species Invasive species Latitudinal gradients in species diversity Minimum viable population Neutral theory Occupancy-abundance relationship Population viability analysis Priority effect Rapoport's rule Relative abundance distribution Relative species abundance Species diversity Species homogeneity Species richness Species distribution Species-area curve Umbrella species Species interaction Antibiosis Biological interaction Commensalism Community ecology Ecological facilitation Interspecific competition Mutualism Storage effect Spatial ecology Biogeography Cross-boundary subsidy Ecocline Ecotone Ecotype Disturbance Edge effect Foster's rule Habitat fragmentation Ideal free distribution Intermediate Disturbance Hypothesis Island biogeography Landscape ecology Landscape epidemiology Landscape limnology Metapopulation Patch dynamics r/K selection theory Source–sink dynamics Niche Ecological niche Ecological trap Ecosystem engineer Environmental niche modelling Guild Habitat Limiting similarity Niche apportionment models Niche construction Niche differentiation Other networks Assembly rules Bateman's principle Bioluminescence Ecological collapse Ecological debt Ecological deficit Ecological energetics Ecological indicator Ecological threshold Ecosystem diversity Emergence Extinction debt Kleiber's law Liebig's law of the minimum Marginal value theorem Thorson's rule Xerosere Other Allometry Alternative stable state Balance of nature Biological data visualization Constructal theory Ecocline Ecological economics Ecological footprint Ecological forecasting Ecological humanities Ecological stoichiometry Ecopath Ecosystem based fisheries Endolith Evolutionary ecology Functional ecology Industrial ecology Macroecology Microecosystem Natural environment Systems ecology Theoretical ecology List of ecology topics