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Thus, heterotrophs – all animals, almost all fungi, as well as most bacteria and protozoa – depend on autotrophs, or primary producers, for the raw materials and fuel they need. Heterotrophs obtain energy by breaking down carbohydrates or oxidizing organic molecules (carbohydrates, fats, and proteins) obtained in food.
Autotrophs use energy from sunlight (photoautotrophs) or oxidation of inorganic compounds (lithoautotrophs) to convert inorganic carbon dioxide to organic carbon compounds and energy to sustain their life. Comparing the two in basic terms, heterotrophs (such as animals) eat either autotrophs (such as plants) or other heterotrophs, or both.
All eukaryotes except for green plants and algae are unable to manufacture their own food: They obtain food from other organisms. This mode of nutrition is also known as heterotrophic nutrition . All heterotrophs (except blood and gut parasites ) have to convert solid food into soluble compounds which are capable of being absorbed (digestion).
Herbivores and carnivores are examples of organisms that obtain carbon and electrons or hydrogen from living organic matter. Chemoorganotrophs are organisms which use the chemical energy in organic compounds as their energy source and obtain electrons or hydrogen from the organic compounds, including sugars (i.e. glucose), fats and proteins. [2]
Autotrophs are classified as either photoautotrophs (which get energy from the sun, like plants) or chemoautotrophs (which get energy from chemical bonds, like certain bacteria). Consumers are typically viewed as predatory animals such as meat-eaters. However, herbivorous animals and parasitic fungi are also consumers.
There are different ecological dimensions that can be mapped to create more complicated food webs, including: species composition (type of species), richness (number of species), biomass (the dry weight of plants and animals), productivity (rates of conversion of energy and nutrients into growth), and stability (food webs over time). A food web ...
Essential amino acids cannot be made by the animal. Some of the amino acids are convertible (with the expenditure of energy) to glucose and can be used for energy production just as ordinary glucose. By breaking down existing protein, some glucose can be produced internally; the remaining amino acids are discarded, primarily as urea in urine.
Food energy is chemical energy that animals (including humans) derive from their food to sustain their metabolism, including their muscular activity. [ 1 ] Most animals derive most of their energy from aerobic respiration , namely combining the carbohydrates , fats , and proteins with oxygen from air or dissolved in water . [ 2 ]