<\/span><\/h2>\nSome organisms, called autotrophs, also known as “self-feeders,” can make their own food, or organic compounds, from simple molecules such as carbon dioxide.<\/span><\/p>\nThere are two main types of autotrophs: Photo autotrophs, such as plants, use energy from sunlight to make organic compounds (sugars) from carbon dioxide in photosynthesis.<\/span><\/p>\nOther examples of photoautotrophs include algae and cyanobacteria.<\/span><\/p>\nChemoautotrophs use energy from chemicals to form organic compounds from carbon dioxide or similar molecules. This is called chemosynthesis. For example, there are chemoautotrophic bacteria that oxidize hydrogen sulfide found in submarine communities where light cannot reach.<\/span><\/p>\nAutotrophs are the basis of the entire ecosystem on the planet. Autotrophs form the basis of food chains and food webs with the energy they capture from light or chemicals. They feed on all other organisms in the community.<\/span><\/p>\nAlso known as other feeders, heterotrophs cannot capture light or chemical energy to extract their own food from carbon dioxide. For example, humans are heterotrophs. Instead, heterotrophs take up organic molecules by eating other organisms or their byproducts.<\/span><\/p>\nAnimals, fungi, and many bacteria are heterotrophs. When we talk about the role of heterotrophs in food chains, we can call them consumers.<\/span><\/p>\n
\n<\/span> Food chain<\/span><\/span><\/h2>\n
<\/span><\/p>\nA food chain is a linear series of organisms through which nutrients and energy pass as a whole. Organisms eat one another. A typical food chain consists of consumers, starting at the bottom and moving upwards.<\/span><\/p>\nPrimary producers are at the base of the food chain. Primary producers are autotrophs. They are mostly photosynthetic organisms such as plants, algae or cyanobacteria. Organisms that eat primary producers are called primary consumers. The primary consumers are usually herbivores, plant eaters, but can be algae eaters or bacteria eaters.<\/span><\/p>\nOrganisms that eat secondary consumers are called tertiary consumers. These are carnivorous carnivores such as eagles or big fish. Some food chains have additional levels, such as quaternary consumers (carnivores that eat tertiary consumers). Organisms that eat primary consumers are called secondary consumers. Secondary consumers are usually meat eaters, i.e. carnivores.<\/span><\/p>\nOrganisms at the top of the food chain are called apex consumers.<\/span><\/p>\nGreen algae are primary producers, primary consumers, eaten by mollusks.<\/span><\/p>\nEach of the above categories is called the trophic level and reflects how many energy and nutrient transfers\u2014how many consumption stages\u2014separate an organism from the original energy source of the food chain, such as light. Assigning organisms to trophic levels is not always clear. For example, humans are omnivores that can eat both plants and animals.<\/span><\/p>\nAs an example of the food chain;<\/span><\/p>\nAquatic plants – fish – heron<\/span><\/p>\nAquatic plant waste – bacteria – shrimp – fish<\/span><\/p>\nPhytoplankton – zooplankton – small sea creatures – Big fish – predators<\/span><\/p>\nGrass- deer- tiger<\/span><\/p>\ngrass-rabbit-fox-wolf<\/span><\/p>\ngrass – sheep – human<\/span><\/p>\n
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