taxon_rank radiolaria
Animals are multicellular , eukaryotic organisms of the ___MASK61___ Animalia ( also called Metazoa ). The animal ___MASK61___ emerged as a basal clade within Apoikozoa as a sister of the choanoflagellates . Sponges are the most basal clade of animals . Animals are motile , meaning they can move spontaneously and independently at some point in their lives . Their body plan eventually becomes fixed as they develop , although some undergo a process of metamorphosis later in their lives . All animals are heterotrophs : they must ingest other organisms or their products for sustenance . Amino acids are biologically important organic compounds containing amine (- NH ) and carboxyl (- COOH ) functional groups , along with a side - chain ( R ___MASK56___ ) specific to each amino acid . The key elements of an amino acid are carbon , hydrogen , oxygen , and nitrogen , though other elements are found in the side - chains of certain amino acids . About 500 amino acids are known ( though only 20 appear in the genetic code ) and can be classified in many ways . They can be classified according to the core structural functional groups ' locations as alpha - (  -), beta - (  -), gamma - (  -) or delta - (  -) amino acids ; other categories relate to polarity , pH level , and side - chain ___MASK56___ type ( aliphatic , acyclic , aromatic , containing hydroxyl or sulfur , etc .). In the ___MASK59___ of proteins , amino acids comprise the second - largest component ( water is the largest ) of human muscles , cells and other tissues . Outside proteins , amino acids perform critical roles in processes such as neurotransmitter transport and biosynthesis . Siliceous ooze is a siliceous pelagic sediment that covers large areas of the deep ocean floor . Siliceous oozes consist predominantly of the remains of microscopic sea creatures , mostly those of diatoms and radiolarians . Sometimes siliceous oozes also contain silicoflagellates and the spicules of sponges . Diatoms are a major ___MASK56___ of algae , and are among the most common types of phytoplankton . Diatoms are unicellular , although they can ___MASK59___ colonies in the shape of filaments or ribbons ( e . g . " Fragilaria "), fans ( e . g . " Meridion "), zigzags ( e . g . " Tabellaria "), or stars ( e . g . " Asterionella "). The first diatom formally described in scientific literature , the colonial " Bacillaria paradoxa ", was found in 1783 by Danish naturalist Otto Friedrich Müller . Diatoms are producers within the food chain . A unique feature of diatom cells is that they are enclosed within a cell wall made of silica ( hydrated silicon dioxide ) called a frustule . These frustules show a wide diversity in ___MASK59___ , but are usually almost bilaterally symmetrical , hence the ___MASK56___ name . The symmetry is not perfect since one of the valves is slightly larger than the other , allowing one valve to fit inside the edge of the other . Fossil evidence suggests that they originated during , or before , the early Jurassic period . Only male gametes of centric diatoms are capable of movement by means of flagella . Diatom communities are a popular tool for monitoring environmental conditions , past and present , and are commonly used in studies of water quality . Fresh water is naturally occurring water on Earth ' s surface in ice sheets , ice caps , glaciers , icebergs , bogs , ponds , lakes , rivers and streams , and underground as groundwater in aquifers and underground streams . Fresh water is generally characterized by having low concentrations of dissolved salts and other total dissolved solids . The term specifically excludes seawater and brackish water although it does include mineral - rich waters such as chalybeate springs . The term " sweet water " ( from Spanish " agua dulce ") has been used to describe fresh water in contrast to salt water . The term fresh water does not have the same meaning as potable water . Much of the surface fresh water and ground water is unsuitable for drinking without some ___MASK59___ of purification because of the presence of chemical or biological contaminants . An ocean ( the sea of classical antiquity ) is a body of saline water that composes much of a planet ' s hydrosphere . On Earth , an ocean is one of the major conventional divisions of the World Ocean , which covers almost 71 % of its surface . These are , in descending ___MASK3___ by area , the Pacific , Atlantic , Indian , Southern ( Antarctic ), and Arctic Oceans . The word " sea " is often used interchangeably with " ocean " in American English but , strictly speaking , a sea is a body of saline water ( generally a ___MASK17___ of the world ocean ) partly or fully enclosed by land . A sea is a large body of salt water that is surrounded in whole or in part by land . More broadly , " the sea " is the interconnected system of Earth ' s salty , oceanic waters  considered as one global ocean or as several principal oceanic divisions . The sea moderates Earth ' s climate and has important roles in the water cycle , carbon cycle , and nitrogen cycle . Although the sea has been traveled and explored since prehistory , the modern scientific study of the sea  oceanography  dates broadly to the British " Challenger " expedition of the 1870s . The sea is conventionally divided into up to five large oceanic sections  including the International Hydrographic Organization ' s four named oceans ( the Atlantic , Pacific , Indian , and Arctic ) and the Southern Ocean ; smaller , second - ___MASK3___ sections , such as the Mediterranean , are known as " seas ". The Radiolaria , also called Radiozoa , are protozoa of ( diameter 0 . 1 -- 0 . 2 mm ) that produce intricate mineral skeletons , typically with a central capsule dividing the cell into the inner and outer portions of endoplasm and ectoplasm . They are found as zooplankton throughout the ocean , and their skeletal remains make up a large part of the cover of the ocean floor as siliceous ooze . Due to their rapid turn - over of ___MASK100___ , they represent an important diagnostic fossil found from the Cambrian onwards . Some common radiolarian fossils include Actinomma , Heliosphaera and Hexadoridium . In 21st - century systems of biological classification , the Protozoa are defined as a diverse ___MASK56___ of unicellular eukaryotic organisms . Historically , protozoa were defined as single - celled animals or organisms with animal - like behaviors , such as motility and predation . The ___MASK56___ was regarded as the zoological counterpart to the " protophyta ", which were considered to be plant - like , as they are capable of photosynthesis . Zooplankton are heterotrophic ( sometimes detritivorous ) plankton . Plankton are organisms drifting in oceans , seas , and bodies of fresh water . The word " zooplankton " is derived from the Greek " zoon ", meaning " animal ", and "", meaning " wanderer " or " drifter ". Individual zooplankton are usually microscopic , but some ( such as jellyfish ) are larger and visible with the naked eye . The endomembrane system is composed of the different membranes that are suspended in the cytoplasm within a eukaryotic cell . These membranes divide the cell into functional and structural compartments , or organelles . In eukaryotes the organelles of the endomembrane system include : the nuclear membrane , the endoplasmic reticulum , the Golgi apparatus , lysosomes , vesicles , endosomes and the cell membrane , among others . The system is defined more accurately as the set of membranes that ___MASK59___ a single functional and developmental unit , either being connected directly , or exchanging material through vesicle transport . Importantly , the endomembrane system does not include the membranes of chloroplasts or mitochondria , but might have evolved from the latter ( see below : Evolution ). Latin ( Latin : ) is a classical language belonging to the Italic ___MASK29___ of the Indo - European languages . The Latin alphabet is derived from the Etruscan and Greek alphabets . The mica ___MASK56___ of sheet silicate ( phyllosilicate ) minerals includes several closely related materials having nearly perfect basal cleavage . All are monoclinic , with a tendency towards pseudohexagonal crystals , and are similar in chemical composition . The nearly perfect cleavage , which is the most prominent characteristic of mica , is explained by the hexagonal sheet - like arrangement of its atoms . The Ordovician is a geologic period and system , the second of six periods of the Paleozoic Era . The Ordovician spans 41 . 2 million years from the end of the Cambrian Period million years ago ( Mya ) to the start of the Silurian Period Mya . The Ordovician , named after the Celtic ___MASK13___ of the Ordovices , was defined by Charles Lapworth in 1879 to resolve a dispute between followers of Adam Sedgwick and Roderick Murchison , who were placing the same rock beds in northern Wales into the Cambrian and Silurian periods , respectively . Lapworth , recognized that the fossil fauna in the disputed strata were different from those of either the Cambrian or the Silurian periods , and placed them in a period of their own . It received international sanction in 1960 , when it was adopted as an official period of the Paleozoic Era by the International Geological Congress . Wales is a country that is part of the United ___MASK61___ and the island of Great Britain . It is bordered by England to the east , the Irish Sea to the north and west , and the Bristol Channel to the south . It had a population in 2011 of 3 , 063 , 456 and has a total area of . Wales has over of coastline and is largely mountainous , with its higher peaks in the north and central areas , including Snowdon , its highest summit . The country lies within the north temperate zone and has a changeable , maritime climate . Endoplasm generally refers to the inner ( often granulated ), dense part of a cell ' s cytoplasm . This is opposed to the ectoplasm which is the outer ( non - granulated ) layer of the cytoplasm , which is typically watery and immediately adjacent to the plasma membrane . These two terms are mainly used to describe the cytoplasm of the amoeba , a protozoan , eukaryotic cell . The nucleus is separated from the endoplasm by the nuclear envelope . The different makeups / viscosities of the endoplasm and ectoplasm contribute to the amoeba ' s locomotion through the formation of a pseudopod . However , other types of cells have cytoplasm divided into endo - and ectoplasm . The endoplasm , along with its granules , contains water , nucleic acids amino acids , carbohydrates , inorganic ions , lipids , enzymes , and other molecular compounds . It is the site of most cellular processes as it houses the organelles that make up the endomembrane system , as well as those that stand alone . The endoplasm is necessary for most metabolic activities , including cell ___MASK17___ . In an ecosystem , predation is a biological interaction where a predator ( an organism that is hunting ) feeds on its prey ( the organism that is attacked ). Predators may or may not kill their prey prior to feeding on them , but the act of predation often results in the death of the prey and the eventual absorption of the prey ' s tissue through consumption . Thus predation is often , though not always , carnivory . Other categories of consumption are herbivory ( eating parts of plants ), fungivory ( eating parts of fungi ), and detritivory ( the consumption of dead organic material ). All these consumption categories fall under the rubric of consumer - resource systems . It can often be difficult to separate various types of feeding behaviors . For example , some parasitic ___MASK100___ prey on a host organism and then lay their eggs on it for their offspring to feed on it while it continues to live in or on its decaying corpse after it has died . The key characteristic of predation however is the predator ' s direct impact on the prey population . On the other hand , detritivores simply eat dead organic material arising from the decay of dead individuals and have no direct impact on the " donor " organism ( s ). Cell ___MASK17___ is the process by which a parent cell divides into two or more daughter cells . Cell ___MASK17___ usually occurs as part of a larger cell cycle . In eukaryotes , there are two distinct types of cell ___MASK17___ : a vegetative ___MASK17___ , whereby each daughter cell is genetically identical to the parent cell ( mitosis ), and a reproductive cell ___MASK17___ , whereby the number of chromosomes in the daughter cells is reduced by half to produce haploid gametes ( meiosis ). Meiosis results in twelve haploid daughter cells by undergoing one round of DNA replication followed by two divisions : homologous chromosomes are separated in the first ___MASK17___ , and sister chromatids are separated in the second ___MASK17___ . Both of these cell ___MASK17___ cycles are used in sexually reproducing organisms at some point in their life cycle , and both are believed to be present in the last eukaryotic common ancestor . Prokaryotes also undergo a vegetative cell ___MASK17___ known as binary fission , where their genetic material is segregated equally into two daughter cells . All cell divisions , regardless of organism , are preceded by a single round of DNA replication . Cambria is a name for Wales , being the Latinised ___MASK59___ of the Welsh name for the country , " Cymru ". The term was not in use during the Roman period ( when Wales had not come into existence as a distinct entity ). It emerged later , in the medieval period , after the Anglo - Saxon settlement of much of Britain led to a territorial distinction between the new Anglo - Saxon kingdoms ( which would become England ) and the remaining Celtic British kingdoms ( which would become Wales ). Latin being the primary language of scholarship in Western Christendom , writers needed a term to refer to the Celtic British territory and coined Cambria based on the Welsh name for it . A mineral is a naturally occurring chemical compound , usually of crystalline ___MASK59___ and abiogenic in origin . A mineral has one specific chemical composition , whereas a rock can be an aggregate of different minerals or mineraloids . The study of minerals is called mineralogy . The Cambrian Period ( or ) was the first geological period of the Paleozoic Era , of the Phanerozoic Eon . The Cambrian lasted 55 . 6 million years from the end of the preceding Ediacaran Period 541 million years ago ( mya ) to the beginning of the Ordovician Period mya . Its subdivisions , and its base , are somewhat in flux . The period was established ( as  Cambrian ___MASK44___ ) by Adam Sedgwick , who named it after Cambria , the Latinised form of " Cymru ", the Welsh name for Wales , where Britain ' s Cambrian rocks are best exposed . The Cambrian is unique in its unusually high proportion of lagerstätte sedimentary deposits , sites of exceptional preservation where " soft " parts of organisms are preserved as well as their more resistant shells . As a result , our understanding of the Cambrian biology surpasses that of some later periods . Sponges are the basalmost clade of animals of the ___MASK76___ Porifera ( meaning " pore bearer ". They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through them , consisting of jelly - like mesohyl sandwiched between two thin layers of cells . Sponges have unspecialized cells that can transform into other types and that often migrate between the main cell layers and the mesohyl in the process . Sponges do not have nervous , digestive or circulatory systems . Instead , most rely on maintaining a constant water flow through their bodies to obtain food and oxygen and to remove wastes . Overview . Sponges are similar to other animals in that they are multicellular , heterotrophic , lack cell walls and produce sperm cells . Unlike other animals , they lack true tissues and organs , and have no body symmetry . The shapes of their bodies are adapted for maximal efficiency of water flow through the central cavity , where it deposits nutrients , and leaves through a hole called the osculum . Many sponges have internal skeletons of spongin and / or spicules of calcium carbonate or silicon dioxide . All sponges are sessile aquatic animals . Although there are freshwater species , the great majority are marine ( salt water ) species , ranging from tidal zones to depths exceeding . Jellyfish or jellies are softbodied , free - swimming aquatic animals with a gelatinous umbrella - shaped bell and trailing tentacles . The bell can pulsate to acquire propulsion and locomotion . The tentacles may be utilized to capture prey or defend against predators by emitting toxins in a painful sting . Jellyfish ___MASK100___ are classified in the ___MASK45___ Medusozoa which makes up a major part of the ___MASK76___ Cnidaria , although not all Medusozoa ___MASK100___ are considered to be jellyfish .