相关背景内容： | Animals are multicellular, eukaryotic organisms of the kingdom Animalia (also called Metazoa). Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their lives. Most animals are motile, meaning they can move spontaneously and independently. All animals must ingest other organisms or their products for sustenance (see Heterotroph).
Most known animal phyla appeared in the fossil record as marine species during the Cambrian explosion, about 542 million years ago. Animals are divided into various sub-groups, some of which are: vertebrates (birds, mammals, amphibians, reptiles, fish); molluscs (clams, oysters, octopuses, squid, snails); arthropods (millipedes, centipedes, insects, spiders, scorpions, crabs, lobsters, shrimp); annelids (earthworms, leeches); sponges; and jellyfish.
All animals are heterotrophs, meaning that they feed directly or indirectly on other living things.[27] They are often further subdivided into groups such as carnivores, herbivores, omnivores, and parasites.[28]
Predation is a biological interaction where a predator (a heterotroph that is hunting) feeds on its prey (the organism that is attacked).[29] Predators may or may not kill their prey prior to feeding on them, but the act of predation almost always results in the death of the prey.[30] The other main category of consumption is detritivory, the consumption of dead organic matter.[31] It can at times be difficult to separate the two feeding behaviours, for example, where parasitic species prey on a host organism and then lay their eggs on it for their offspring to feed on its decaying corpse. Selective pressures imposed on one another has led to an evolutionary arms race between prey and predator, resulting in various antipredator adaptations.[32]
Most animals indirectly use the energy of sunlight by eating plants or plant-eating animals. Most plants use light to convert inorganic molecules in their environment into carbohydrates, fats, proteins and other biomolecules, characteristically containing reduced carbon in the form of carbon-hydrogen bonds. Starting with carbon dioxide (CO2) and water (H2O), photosynthesis converts the energy of sunlight into chemical energy in the form of simple sugars (e.g., glucose), with the release of molecular oxygen. These sugars are then used as the building blocks for plant growth, including the production of other biomolecules.[10] When an animal eats plants (or eats other animals which have eaten plants), the reduced carbon compounds in the food become a source of energy and building materials for the animal.[33] They are either used directly to help the animal grow, or broken down, releasing stored solar energy, and giving the animal the energy required for motion.[34][35]
Animals living close to hydrothermal vents and cold seeps on the ocean floor are not dependent on the energy of sunlight.[36] Instead chemosynthetic archaea and bacteria form the base of the food chain.[37]
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相关背景内容： | Grains are small, hard, dry seeds, with or without attached hulls or fruit layers, harvested for human or animal consumption.[1] Agronomists also call the plants producing such seeds "grain crops". The two main types of commercial grain crops are cereals such as wheat and rye, and legumes such as beans and soybeans.
After being harvested, dry grains are more durable than other staple foods such as starchy fruits like plantains and breadfruit and tubers like sweet potatoes and cassava. This durability has made grains well suited to industrial agriculture, since they can be mechanically harvested, transported by rail or ship, stored for long periods in silos, and milled for flour or pressed for oil. Thus, major global commodity markets exist for canola, maize, rice, soybeans, wheat, and other grains but not for tubers, vegetables, or other crops.
In botany, grains and cereals are synonymous with caryopses, the fruits of the grass family. In agronomy and commerce, seeds or fruits from other plant families are called grains if they resemble caryopses. For example, amaranth is sold as "grain amaranth", and amaranth products may be described as "whole grains". The pre-Hispanic civilizations of the Andes had grain-based food systems but, at the higher elevations, none of the grains was a cereal. All three grains native to the Andes are broad-leafed plants rather than grasses such as corn, rice, and wheat.[2] |
相关背景内容： | Sea turtles (superfamily Chelonioidea), sometimes called marine turtles[3] are reptiles of the order of Testudines. There are seven species of sea turtles. They are the leatherback sea turtle, green sea turtle, loggerhead sea turtle, Kemp's ridley sea turtle, hawksbill sea turtle, flatback sea turtle and olive ridley sea turtle. Four of the species have been identified as "endangered" or "critically endangered" with another two being classed as "vulnerable".
Sea turtles, along with other turtles and tortoises, are part of the order Testudines.
The seven living species of sea turtles are: leatherback sea turtle, green sea turtle, loggerhead sea turtle, Kemp's ridley sea turtle, hawksbill sea turtle, flatback sea turtle and olive ridley sea turtle.[4] All species except the leatherback are in the family Cheloniidae. The leatherback belongs to the family Dermochelyidae and is its only member.
The species are primarily distinguished by their anatomy: for instance, the prefrontal scales on the head, the number of and shape of scutes on the carapace, and the type of inframarginal scutes on the plastron. The leatherback is the only sea turtle that does not have a hard shell; instead, it bears a mosaic of bony plates beneath its leathery skin. It is the largest sea turtle, measuring 6 to 9 feet (1.8 to 2.7 m) in length at maturity, and 3 to 5 feet (0.91 to 1.52 m) in width, weighing up to 1,500 pounds (680 kg). Other species are smaller, being mostly 2 to 4 feet (0.61 to 1.22 m) and proportionally narrower.[5][not in citation given]
Sea turtles constitute a single radiation that became distinct from all other turtles at least 110 million years ago.
Sea turtles feed on a wide range of animals and plants. They are mostly omnivorous in their adult life, except the green sea turtle which is herbivorous, changing from a carnivorous diet when young. This diet shift has an effect on the green turtle's morphology. The turtles switch from an omnivorous diet of planktonic material as juveniles to an herbivorous diet of algae and seagrass material as adults, and there is a concurrent transformation of skull morphology.[20] This reflects how the morphological characteristics of turtles are correlated with the foods they consume. Some species specialise on certain prey; sea sponges are the principal food of hawksbill sea turtles, constituting 70–95% of their diets in the Caribbean.[21] Leatherback turtles feed almost exclusively on jellyfish and help control jellyfish populations.[22][23]
Aside from sponges, hawksbills also feed on algae and cnidarians (including the Portuguese man o' war), comb jellies and other jellyfish and sea anemones.[24] Green sea turtles are commonly found in seagrass meadows closer inshore as herbivorous grazers. The leatherback turtle eats a variety of organisms such as seagrass, marine invertebrates including molluscs, jellyfish and shrimp and also fishes. It also consumes of soft coral, sea cucumbers and other soft-bodied creatures.[25] The loggerhead sea turtle is omnivorous, feeding mainly on bottom-dwelling invertebrates, such as gastropods, bivalves, and decapods. The loggerhead has a greater list of known prey than any other sea turtle. Other food items include sponges, corals, sea pens, polychaete worms, sea anemones, cephalopods, barnacles, brachiopods, isopods, insects, bryozoans, sea urchins, sand dollars, sea cucumbers, starfish, fish (eggs, juveniles, and adults), hatchling turtles (including members of its own species), algae, and vascular plants.[26] During migration through the open sea, loggerheads eat jellyfish, floating molluscs, floating egg clusters, squid, and flying fish.[27] The Kemp's ridley turtle feeds on molluscs, crustaceans, jellyfish, algae or seaweed, and sea urchins. The olive ridley turtle is predominantly carnivorous, especially in immature stages of the life cycle. Animal prey consists of protochordates or invertebrates, which can be caught in shallow marine waters or estuarine habitats. Common prey items include jellyfish, tunicates, sea urchins, bryozoans, bivalves, snails, shrimp, crabs, rock lobsters, and sipunculid worms.[28] Aside from jellyfish, leatherbacks also feed on other soft-bodied organisms, such as tunicates and cephalopods.[29] |
