In a given ecosystem, food forms a
web of interlocking
chains with
primary producers at the bottom and
apex predators at the top. Other aspects of the web include
detrovores (that eat
detritis) and
decomposers (that break down dead organisms). Primary consumers are the
herbivores that consume the plants, and secondary consumers are the
carnivores that consume those herbivores. Some organisms, including most mammals and birds, have diets consisting of both animals and plants, and are considered omnivores. The chain ends with the apex predators, the animals that have no known predators in its ecosystem. Humans are considered apex predators. Humans are omnivores, finding sustenance in vegetables, fruits, cooked meat, milk, eggs, mushrooms and seaweed.
Corn (maize), wheat, and rice account for 87% of all grain production worldwide. Just over half of the world's crops are used to feed humans (55 percent), with 36 percent grown as animal feed and 9 percent for
biofuels. Fungi and bacteria are also used in the preparation of
fermented foods like
bread,
wine,
cheese and
yogurt.
Photosynthesis During
photosynthesis, energy from the sun is absorbed and used to transform water and carbon dioxide in the air or soil into oxygen and glucose. The oxygen is then released, and the glucose stored as an energy reserve. Photosynthetic plants, algae and certain bacteria often represent the lowest point of the food chains, making photosynthesis the primary source of energy and food for nearly all life on earth.
Plants also absorb important nutrients and minerals from the air, natural waters, and soil. Carbon, oxygen and hydrogen are absorbed from the air or water and are the basic nutrients needed for plant survival. The three main nutrients absorbed from the soil for plant growth are nitrogen, phosphorus and potassium, with other important nutrients including calcium, sulfur, magnesium, iron boron, chlorine, manganese, zinc, copper molybdenum and nickel. Bacteria provide a source of food for protozoa, who in turn provide a source of food for other organisms such as small invertebrates. Other organisms that feed on bacteria include nematodes, fan worms, shellfish and a species of snail. In the marine environment, plankton (which includes
bacteria,
archaea,
algae,
protozoa and microscopic
fungi) provide a crucial source of food to many small and large aquatic organisms. Without bacteria, life would scarcely exist because bacteria convert atmospheric nitrogen into nutritious
ammonia. Ammonia is the precursor to proteins, nucleic acids, and most vitamins. Since the advent of the industrial process for nitrogen fixation, the
Haber-Bosch Process, the majority of ammonia in the world is human-made.
Plants Plants as a food source are divided into seeds, fruits, vegetables, legumes, grains and nuts. Where plants fall within these categories can vary, with botanically described fruits such as the tomato, squash, pepper and eggplant or seeds like peas commonly considered vegetables. Food is a fruit if the part eaten is derived from the
reproductive tissue, so seeds, nuts and grains are technically fruit. From a culinary perspective, fruits are generally considered the remains of botanically described fruits after grains, nuts, seeds and fruits used as vegetables are removed. and pulses coming from the
Fabaceae (legume) family.
Whole grains are foods that contain all the elements of the original seed (bran, germ, and
endosperm). Nuts are dry fruits, distinguishable by their woody shell. Fleshy fruits (distinguishable from dry fruits like grain, seeds and nuts) can be further classified as
stone fruits (cherries and peaches),
pome fruits (apples, pears),
berries (blackberry, strawberry),
citrus (oranges, lemon),
melons (watermelon, cantaloupe), Mediterranean fruits (grapes, fig),
tropical fruits (banana, pineapple). These include
root vegetables (potatoes and carrots), bulbs (onion family), flowers (cauliflower and broccoli),
leaf vegetables (
spinach and lettuce) and
stem vegetables (celery and
asparagus).
potassium, dietary fiber,
folate and vitamins and low in fat and calories. Grains are more starch based Complicated chemical interactions can enhance or depress bioavailability of certain nutrients.
Phytates can prevent the release of some sugars and vitamins. while leaf and shoot eaters are
folivores (pandas) and wood eaters termed
xylophages (termites).
Frugivores include a diverse range of species from annelids to elephants, chimpanzees and many birds. About 182 fish consume seeds or fruit. Animals (domesticated and wild) use as many types of grasses that have adapted to different locations as their main source of nutrients. Humans eat thousands of plant species; there may be as many as 75,000 edible species of
angiosperms, of which perhaps 7,000 are often eaten. Plants can be processed into breads, pasta, cereals, juices and jams or raw ingredients such as sugar, herbs, spices and oils can be extracted. Many plants and animals have
coevolved in such a way that the fruit is a good source of nutrition for the animal, who then excretes the seeds some distance away, allowing greater dispersal. Even
seed predation can be mutually beneficial, as some seeds can survive the digestion process. Insects are major eaters of seeds, with ants being the only real seed dispersers. Birds, although being major dispersers, only rarely eat seeds as a source of food and can be identified by their thick beak that is used to crack open the seed coat. Mammals eat a more diverse range of seeds, as they are able to crush harder and larger seeds with their teeth.
Animals Animals are used as food either directly or indirectly. This includes meat, eggs, shellfish and dairy products like milk and cheese. They are an important source of protein and are considered complete proteins for human consumption as they contain all the essential amino acids that the human body needs. One steak, chicken breast or pork chop contains about 30 grams of protein. One large egg has 7 grams of protein. A serving of cheese has about 15 grams of protein. And of milk has about 8 grams of protein. ==Taste==