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Branchiopoda Genera
Branchiopoda is a class of crustaceans. It comprises fairy shrimp, clam shrimp, Diplostraca (or Cladocera), Notostraca and the Devonian ''Lepidocaris''. They are mostly small, freshwater animals that feed on plankton and detritus. Description Members of the Branchiopoda are unified by the presence of gills on many of the animals' appendages, including some of the mouthparts. This is also responsible for the name of the group (from the grc, βράγχια, gills, akin to , windpipe; el, πούς, foot). They generally possess compound eyes and a carapace, which may be a shell of two valves enclosing the trunk (as in most Cladocera), broad and shallow (as in the Notostraca), or entirely absent (as in the Anostraca). In the groups where the carapace prevents the use of the trunk limbs for swimming (Cladocera, clam shrimp and the extinct Lipostraca), the antennae are used for locomotion, as they are in the nauplius. Male fairy shrimp have an enlarged pair of antennae with which ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Triops
''Triops'' is a genus of small crustaceans in the order Notostraca (tadpole shrimp). The long-lasting resting eggs of several species of ''Triops'' are commonly sold in kits as a pet. The animals hatch upon contact with fresh water. Most adult-stage ''Triops'' have a life expectancy of up to 90 days and can tolerate a pH range of 6–10. In nature, they often inhabit temporary pools. Relatives and fossil record The genus ''Triops'' can be distinguished from the only other living genus of Notostraca, ''Lepidurus'', by the form of the telson (the end of its 'tail'), which bears only a pair of long, thin caudal extensions in ''Triops'', while ''Lepidurus'' also bears a central platelike process. Only 24 hours after hatching they already resemble miniature versions of the adult form. ''Triops'' are sometimes called "living fossils", since fossils that have been attributed to this genus have been found in rocks hundreds of millions of years old. However, careful analysis of these ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Compound Eye
A compound eye is a visual organ found in arthropods such as insects and crustaceans. It may consist of thousands of ommatidia, which are tiny independent photoreception units that consist of a cornea, lens, and photoreceptor cells which distinguish brightness and color. The image perceived by this arthropod eye is a combination of inputs from the numerous ommatidia, which are oriented to point in slightly different directions. Compared with single-aperture eyes, compound eyes have poor image resolution; however, they possess a very large view angle and the ability to detect fast movement and, in some cases, the polarization of light. Because a compound eye is made up of a collection of ommatidia, each with its own lens, light will enter each ommatidium instead of using a single entrance point. The individual light receptors behind each lens are then turned on and off due to a series of changes in the light intensity during movement or when an object in moving, creating a flic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vernal Pool
Vernal pools, also called vernal ponds or ephemeral pools, are seasonal pools of water that provide habitat for distinctive plants and animals. They are considered to be a distinctive type of wetland usually devoid of fish, and thus allow the safe development of natal amphibian and insect species unable to withstand competition or predation by fish. Certain tropical fish lineages (such as killifishes) have however adapted to this habitat specifically. Vernal pools are a type of wetland. They can be surrounded by many communities/species including deciduous forest, grassland, lodgepole pine forest, blue oak woodland, sagebrush steppe, succulent coastal scrub and prairie. These pools are characteristic of Mediterranean climates, but occur in many other ecosystems. Generation and annual development During most years, a vernal pool basin will experience inundation from rain/precipitation, followed by desiccation from evapotranspiration. These conditions are commonly associated with M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Freshwater
Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include non- salty mineral-rich waters such as chalybeate springs. Fresh water may encompass frozen and meltwater in ice sheets, ice caps, glaciers, snowfields and icebergs, natural precipitations such as rainfall, snowfall, hail/ sleet and graupel, and surface runoffs that form inland bodies of water such as wetlands, ponds, lakes, rivers, streams, as well as groundwater contained in aquifers, subterranean rivers and lakes. Fresh water is the water resource that is of the most and immediate use to humans. Water is critical to the survival of all living organisms. Many organisms can thrive on salt water, but the great majority of higher plants and most insects, amphibians, reptiles, mammals and birds need fresh water to survive. Fresh wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cladocera
The Diplostraca or Cladocera, commonly known as water fleas, are a superorder of small crustaceans that feed on microscopic chunks of organic matter (excluding some predatory forms). Over 1000 species have been recognised so far, with many more undescribed. The oldest fossils of diplostracans date to the Jurassic, though their modern morphology suggests that they originated substantially earlier, during the Paleozoic. Some have also adapted to a life in the ocean, the only members of Branchiopoda to do so, even if several anostracans live in hypersaline lakes. Most are long, with a down-turned head with a single median compound eye, and a carapace covering the apparently unsegmented thorax and abdomen. Most species show cyclical parthenogenesis, where asexual reproduction is occasionally supplemented by sexual reproduction, which produces resting eggs that allow the species to survive harsh conditions and disperse to distant habitats. Description They are mostly long, with t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Food
Food is any substance consumed by an organism for nutritional support. Food is usually of plant, animal, or fungal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals. The substance is ingested by an organism and assimilated by the organism's cells to provide energy, maintain life, or stimulate growth. Different species of animals have different feeding behaviours that satisfy the needs of their unique metabolisms, often evolved to fill a specific ecological niche within specific geographical contexts. Omnivorous humans are highly adaptable and have adapted to obtain food in many different ecosystems. The majority of the food energy required is supplied by the industrial food industry, which produces food with intensive agriculture and distributes it through complex food processing and food distribution systems. This system of conventional agriculture relies heavily on fossil fuels, which means that the food and agricu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as well as with other compounds. Oxygen is Earth's most abundant element, and after hydrogen and helium, it is the third-most abundant element in the universe. At standard temperature and pressure, two atoms of the element bind to form dioxygen, a colorless and odorless diatomic gas with the formula . Diatomic oxygen gas currently constitutes 20.95% of the Earth's atmosphere, though this has changed considerably over long periods of time. Oxygen makes up almost half of the Earth's crust in the form of oxides.Atkins, P.; Jones, L.; Laverman, L. (2016).''Chemical Principles'', 7th edition. Freeman. Many major classes of organic molecules in living organisms contain oxygen atoms, such as proteins, nucleic acids, carbohydrates, and fats, as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metachronal Rhythm
A metachronal rhythm or metachronal wave refers to wavy movements produced by the sequential action (as opposed to synchronized) of structures such as cilia, segments of worms, or legs. These movements produce the appearance of a travelling wave. A Mexican wave is a large scale example of a metachronal wave. This pattern is found widely in nature such as on the cilia of many aquatic organisms such as ctenophores, molluscs, ciliates as well as on the epithelial surfaces of many body organs. Individual cilia, when part of a metachronal wave being used for protist locomotion, individually beat in a pattern similar to the planar stroke of a flagellum. The difference is that the recovery stroke is at 90 degrees to the power stroke, so that the cilia avoid hitting each other. Metachronal rhythms may be seen in the coordinated movements of the legs of millipedes and other multi-legged land invertebrates, as well as in the coordinated movements of social insects. Such metachronal mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vestigiality
Vestigiality is the retention, during the process of evolution, of genetically determined structures or attributes that have lost some or all of the ancestral function in a given species. Assessment of the vestigiality must generally rely on comparison with homologous features in related species. The emergence of vestigiality occurs by normal evolutionary processes, typically by loss of function of a feature that is no longer subject to positive selection pressures when it loses its value in a changing environment. The feature may be selected against more urgently when its function becomes definitively harmful, but if the lack of the feature provides no advantage, and its presence provides no disadvantage, the feature may not be phased out by natural selection and persist across species. Examples of vestigial structures (also called degenerate, atrophied, or rudimentary organs) are the loss of functional wings in island-dwelling birds; the human vomeronasal organ; and the hi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bottom Feeder
A bottom feeder is an aquatic animal that feeds on or near the bottom of a body of water. Biologists often use the terms ''benthos''—particularly for invertebrates such as shellfish, crabs, crayfish, sea anemones, starfish, snails, bristleworms and sea cucumbers—and ''benthivore'' or ''benthivorous'', for fish and invertebrates that feed on material from the bottom. However the term benthos includes all aquatic life that lives on or near the bottom, which means it also includes non-animals, such as plants and algae. Biologists also use specific terms that refer to bottom feeding fish, such as demersal fish, groundfish, benthic fish and benthopelagic fish. Examples of bottom feeding fish species groups are flatfish (halibut, flounder, plaice, sole), eels, cod, haddock, bass, grouper, carp, bream ( snapper) and some species of catfish and shark. Feeding strategies Some bottom feeders are detritivores taking advantage of organic materials that sink down through ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nauplius (larva)
Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a ecdysis, moult, in which the hard exoskeleton is shed to allow the animal to grow. The larvae of crustaceans often bear little resemblance to the adult, and there are still cases where it is not known what larvae will grow into what adults. This is especially true of crustaceans which live as benthic adults (on the sea bed), more-so than where the larvae are planktonic, and thereby easily caught. Many crustacean larvae were not immediately recognised as larvae when they were discovered, and were described as new genera and species. The names of these genera have become generalised to cover specific larval stages across wide groups of crustaceans, such as ''zoea'' and ''nauplius''. Other terms described forms which are only found in particular groups, such as the ''glaucothoe'' of hermit crabs, or the ''phyllosoma'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antenna (biology)
Antennae ( antenna), sometimes referred to as "feelers", are paired appendages used for sensing in arthropods. Antennae are connected to the first one or two segments of the arthropod head. They vary widely in form but are always made of one or more jointed segments. While they are typically sensory organs, the exact nature of what they sense and how they sense it is not the same in all groups. Functions may variously include sensing touch, air motion, heat, vibration (sound), and especially smell or taste. Antennae are sometimes modified for other purposes, such as mating, brooding, swimming, and even anchoring the arthropod to a substrate. Larval arthropods have antennae that differ from those of the adult. Many crustaceans, for example, have free-swimming larvae that use their antennae for swimming. Antennae can also locate other group members if the insect lives in a group, like the ant. The common ancestor of all arthropods likely had one pair of uniramous (unbranched ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
