Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can be released to fuel the organisms' activities. This chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water – hence the name photosynthesis, from the Greek φῶς, phōs, "light", σύνθεσις, synthesis, "putting together". In most cases, oxygen is released as a waste product. Most plants, most algae, cyanobacteria perform photosynthesis. Photosynthesis is responsible for producing and maintaining the oxygen content of the Earth's atmosphere, supplies all of the organic compounds and most of the energy necessary for life on Earth. Although photosynthesis is performed differently by different species, the process always begins when energy from light is absorbed by proteins called reaction centres that contain green chlorophyll pigments. In plants, these proteins are held inside organelles called chloroplasts, which are most abundant in leaf cells, while in bacteria they are embedded in the plasma membrane.
In these light-dependent reactions, some energy is used to strip electrons from suitable substances, such as water, producing oxygen gas. The hydrogen freed by the splitting of water is used in the creation of two further compounds that serve as short-term stores of energy, enabling its transfer to drive other reactions: these compounds are reduced nicotinamide adenine dinucleotide phosphate and adenosine triphosphate, the "energy currency" of cells. In plants and cyanobacteria, long-term energy storage in the form of sugars is produced by a subsequent sequence of light-independent reactions called the Calvin cycle. In the Calvin cycle, atmospheric carbon dioxide is incorporated into existing organic carbon compounds, such as ribulose bisphosphate. Using the ATP and NADPH produced by the light-dependent reactions, the resulting compounds are reduced and removed to form further carbohydrates, such as glucose; the first photosynthetic organisms evolved early in the evolutionary history of life and most used reducing agents such as hydrogen or hydrogen sulfide, rather than water, as sources of electrons.
Cyanobacteria appeared later. Today, the average rate of energy capture by photosynthesis globally is 130 terawatts, about eight times the current power consumption of human civilization. Photosynthetic organisms convert around 100–115 billion tonnes of carbon into biomass per year. Photosynthetic organisms are photoautotrophs, which means that they are able to synthesize food directly from carbon dioxide and water using energy from light. However, not all organisms use carbon dioxide as a source of carbon atoms to carry out photosynthesis. In plants and cyanobacteria, photosynthesis releases oxygen; this is called oxygenic photosynthesis and is by far the most common type of photosynthesis used by living organisms. Although there are some differences between oxygenic photosynthesis in plants and cyanobacteria, the overall process is quite similar in these organisms. There are many varieties of anoxygenic photosynthesis, used by certain types of bacteria, which consume carbon dioxide but do not release oxygen.
Carbon dioxide is converted into sugars in a process called carbon fixation. Carbon fixation is an endothermic redox reaction. In general outline, photosynthesis is the opposite of cellular respiration: while photosynthesis is a process of reduction of carbon dioxide to carbohydrate, cellular respiration is the oxidation of carbohydrate or other nutrients to carbon dioxide. Nutrients used in cellular respiration include amino acids and fatty acids; these nutrients are oxidized to produce carbon dioxide and water, to release chemical energy to drive the organism's metabolism. Photosynthesis and cellular respiration are distinct processes, as they take place through different sequences of chemical reactions and in different cellular compartments; the general equation for photosynthesis as first proposed by Cornelis van Niel is therefore: CO2carbondioxide + 2H2Aelectron donor + photonslight energy → carbohydrate + 2Aoxidizedelectrondonor + H2OwaterSince water is used as the electron donor in oxygenic photosynthesis, the equation for this process is: CO2carbondioxide + 2H2Owater + photonslight energy → carbohydrate + O2oxygen + H2OwaterThis equation emphasizes that water is both a reactant in the light-dependent reaction and a product of the light-independent reaction, but canceling n water molecules from each side gives the net equation: CO2carbondioxide + H2O water + photonslight energy → carbohydrate + O2 oxygen Other processes substitute other compounds for water in the electron-supply role.
In the first stage, light-dependent reactions or light reactions capture the energy of light and use it to make the energy-storage molecules ATP and NADPH. During the second stage, the light-independent reactions use these products to capture and reduce carbon dioxid
Binomial nomenclature called binominal nomenclature or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, although they can be based on words from other languages. Such a name is called a binomen, binominal name or a scientific name; the first part of the name – the generic name – identifies the genus to which the species belongs, while the second part – the specific name or specific epithet – identifies the species within the genus. For example, humans belong within this genus to the species Homo sapiens. Tyrannosaurus rex is the most known binomial; the formal introduction of this system of naming species is credited to Carl Linnaeus beginning with his work Species Plantarum in 1753. But Gaspard Bauhin, in as early as 1623, had introduced in his book Pinax theatri botanici many names of genera that were adopted by Linnaeus; the application of binomial nomenclature is now governed by various internationally agreed codes of rules, of which the two most important are the International Code of Zoological Nomenclature for animals and the International Code of Nomenclature for algae and plants.
Although the general principles underlying binomial nomenclature are common to these two codes, there are some differences, both in the terminology they use and in their precise rules. In modern usage, the first letter of the first part of the name, the genus, is always capitalized in writing, while that of the second part is not when derived from a proper noun such as the name of a person or place. Both parts are italicized when a binomial name occurs in normal text, thus the binomial name of the annual phlox is now written as Phlox drummondii. In scientific works, the authority for a binomial name is given, at least when it is first mentioned, the date of publication may be specified. In zoology "Patella vulgata Linnaeus, 1758"; the name "Linnaeus" tells the reader who it was that first published a description and name for this species of limpet. "Passer domesticus". The original name given by Linnaeus was Fringilla domestica; the ICZN does not require that the name of the person who changed the genus be given, nor the date on which the change was made, although nomenclatorial catalogs include such information.
In botany "Amaranthus retroflexus L." – "L." is the standard abbreviation used in botany for "Linnaeus". "Hyacinthoides italica Rothm. – Linnaeus first named this bluebell species Scilla italica. The name is composed of two word-forming elements: "bi", a Latin prefix for two, "-nomial", relating to a term or terms; the word "binomium" was used in Medieval Latin to mean a two-term expression in mathematics. Prior to the adoption of the modern binomial system of naming species, a scientific name consisted of a generic name combined with a specific name, from one to several words long. Together they formed a system of polynomial nomenclature; these names had two separate functions. First, to designate or label the species, second, to be a diagnosis or description. In a simple genus, containing only two species, it was easy to tell them apart with a one-word genus and a one-word specific name; such "polynomial names" may sometimes look like binomials, but are different. For example, Gerard's herbal describes various kinds of spiderwort: "The first is called Phalangium ramosum, Branched Spiderwort.
The other... is aptly termed Phalangium Ephemerum Virginianum, Soon-Fading Spiderwort of Virginia". The Latin phrases are short descriptions, rather than identifying labels; the Bauhins, in particular Caspar Bauhin, took some important steps towards the binomial system, by pruning the Latin descriptions, in many cases to two words. The adoption by biologists of a system of binomial nomenclature is due to Swedish botanist and physician Carl von Linné, more known by his Latinized name Carl Linnaeus, it was in his 1753 Species Plantarum that he first began using a one-word "trivial name" together with a generic name in a system of binomial nomenclature. This trivial name is what is now known as specific name; the Bauhins' genus names were retained in many of these, but the descriptive part was reduced to a single word. Linnaeus's trivial names introduced an important new idea, namely that the function of a name could be to give a species a unique label; this meant. Thus Gerard's Phalangium ephemerum virginianum became Tradescantia virgi
A flagellum is a lash-like appendage that protrudes from the cell body of certain bacteria and eukaryotic cells termed as flagellates. A flagellate can have several flagella; the primary function of a flagellum is that of locomotion, but it often functions as a sensory organelle, being sensitive to chemicals and temperatures outside the cell. The similar structure in the archaea functions in the same way but is structurally different and has been termed the archaellum. Flagella are organelles defined by function rather than structure. Flagella vary greatly. Both prokaryotic and eukaryotic flagella can be used for swimming but they differ in protein composition and mechanism of propulsion; the word flagellum in Latin means whip. An example of a flagellated bacterium is the ulcer-causing Helicobacter pylori, which uses multiple flagella to propel itself through the mucus lining to reach the stomach epithelium. An example of a eukaryotic flagellate cell is the mammalian sperm cell, which uses its flagellum to propel itself through the female reproductive tract.
Eukaryotic flagella are structurally identical to eukaryotic cilia, although distinctions are sometimes made according to function or length. Fimbriae and pili are thin appendages, but have different functions and are smaller. Three types of flagella have so far been distinguished: bacterial and eukaryotic; the main differences among these three types are: Bacterial flagella are helical filaments, each with a rotary motor at its base which can turn clockwise or counterclockwise. They provide two of several kinds of bacterial motility. Archaeal flagella are superficially similar to bacterial flagella, but are different in many details and considered non-homologous. Eukaryotic flagella—those of animal and protist cells—are complex cellular projections that lash back and forth. Eukaryotic flagella are classed along with eukaryotic motile cilia as undulipodia to emphasize their distinctive wavy appendage role in cellular function or motility. Primary cilia are immotile, are not undulipodia; the bacterial flagellum is made up of the protein flagellin.
Its shape is a 20-nanometer-thick hollow tube. It has a sharp bend just outside the outer membrane. A shaft runs between the hook and the basal body, passing through protein rings in the cell's membrane that act as bearings. Gram-positive organisms have two of these basal body rings, one in the peptidoglycan layer and one in the plasma membrane. Gram-negative organisms have four such rings: the L ring associates with the lipopolysaccharides, the P ring associates with peptidoglycan layer, the M ring is embedded in the plasma membrane, the S ring is directly attached to the plasma membrane; the filament ends with a capping protein. The flagellar filament is the long, helical screw that propels the bacterium when rotated by the motor, through the hook. In most bacteria that have been studied, including the Gram-negative Escherichia coli, Salmonella typhimurium, Caulobacter crescentus, Vibrio alginolyticus, the filament is made up of 11 protofilaments parallel to the filament axis; each protofilament is a series of tandem protein chains.
However, Campylobacter jejuni has seven protofilaments. The basal body has several traits in common with some types of secretory pores, such as the hollow, rod-like "plug" in their centers extending out through the plasma membrane; the similarities between bacterial flagella and bacterial secretory system structures and proteins provide scientific evidence supporting the theory that bacterial flagella evolved from the type-three secretion system. The bacterial flagellum is driven by a rotary engine made up of protein, located at the flagellum's anchor point on the inner cell membrane; the engine is powered by proton motive force, i.e. by the flow of protons across the bacterial cell membrane due to a concentration gradient set up by the cell's metabolism. The rotor transports protons across the membrane, is turned in the process; the rotor alone can operate at 6,000 to 17,000 rpm, but with the flagellar filament attached only reaches 200 to 1000 rpm. The direction of rotation can be changed by the flagellar motor switch instantaneously, caused by a slight change in the position of a protein, FliG, in the rotor.
The flagellum is energy efficient and uses little energy. The exact mechanism for torque generation is still poorly understood; because the flagellar motor has no on-off switch, the protein epsE is used as a mechanical clutch to disengage the motor from the rotor, thus stopping the flagellum and allowing the bacterium to remain in one place. The cylindrical shape of flagella is suited to locomotion of microscopic organisms; the rotational speed of flagella varies in response to the intensity of the proton motive force, thereby permitting certain forms of speed control, permitting some types of bacteria to attain remarkable speeds in proportion to their size. At such a speed, a bacterium would take about 245 days to cover 1 km. In comparison to macroscopic life forms, it is fast indeed when expressed in terms of number of body lengths p
Animals are multicellular eukaryotic organisms that form the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, grow from a hollow sphere of cells, the blastula, during embryonic development. Over 1.5 million living animal species have been described—of which around 1 million are insects—but it has been estimated there are over 7 million animal species in total. Animals range in length from 8.5 millionths of a metre to 33.6 metres and have complex interactions with each other and their environments, forming intricate food webs. The category includes humans, but in colloquial use the term animal refers only to non-human animals; the study of non-human animals is known as zoology. Most living animal species are in the Bilateria, a clade whose members have a bilaterally symmetric body plan; the Bilateria include the protostomes—in which many groups of invertebrates are found, such as nematodes and molluscs—and the deuterostomes, containing the echinoderms and chordates.
Life forms interpreted. Many modern animal phyla became established in the fossil record as marine species during the Cambrian explosion which began around 542 million years ago. 6,331 groups of genes common to all living animals have been identified. Aristotle divided animals into those with those without. Carl Linnaeus created the first hierarchical biological classification for animals in 1758 with his Systema Naturae, which Jean-Baptiste Lamarck expanded into 14 phyla by 1809. In 1874, Ernst Haeckel divided the animal kingdom into the multicellular Metazoa and the Protozoa, single-celled organisms no longer considered animals. In modern times, the biological classification of animals relies on advanced techniques, such as molecular phylogenetics, which are effective at demonstrating the evolutionary relationships between animal taxa. Humans make use of many other animal species for food, including meat and eggs. Dogs have been used in hunting, while many aquatic animals are hunted for sport.
Non-human animals have appeared in art from the earliest times and are featured in mythology and religion. The word "animal" comes from the Latin animalis, having soul or living being; the biological definition includes all members of the kingdom Animalia. In colloquial usage, as a consequence of anthropocentrism, the term animal is sometimes used nonscientifically to refer only to non-human animals. Animals have several characteristics. Animals are eukaryotic and multicellular, unlike bacteria, which are prokaryotic, unlike protists, which are eukaryotic but unicellular. Unlike plants and algae, which produce their own nutrients animals are heterotrophic, feeding on organic material and digesting it internally. With few exceptions, animals breathe oxygen and respire aerobically. All animals are motile during at least part of their life cycle, but some animals, such as sponges, corals and barnacles become sessile; the blastula is a stage in embryonic development, unique to most animals, allowing cells to be differentiated into specialised tissues and organs.
All animals are composed of cells, surrounded by a characteristic extracellular matrix composed of collagen and elastic glycoproteins. During development, the animal extracellular matrix forms a flexible framework upon which cells can move about and be reorganised, making the formation of complex structures possible; this may be calcified, forming structures such as shells and spicules. In contrast, the cells of other multicellular organisms are held in place by cell walls, so develop by progressive growth. Animal cells uniquely possess the cell junctions called tight junctions, gap junctions, desmosomes. With few exceptions—in particular, the sponges and placozoans—animal bodies are differentiated into tissues; these include muscles, which enable locomotion, nerve tissues, which transmit signals and coordinate the body. There is an internal digestive chamber with either one opening or two openings. Nearly all animals make use of some form of sexual reproduction, they produce haploid gametes by meiosis.
These fuse to form zygotes, which develop via mitosis into a hollow sphere, called a blastula. In sponges, blastula larvae swim to a new location, attach to the seabed, develop into a new sponge. In most other groups, the blastula undergoes more complicated rearrangement, it first invaginates to form a gastrula with a digestive chamber and two separate germ layers, an external ectoderm and an internal endoderm. In most cases, a third germ layer, the mesoderm develops between them; these germ layers differentiate to form tissues and organs. Repeated instances of mating with a close relative during sexual reproduction leads to inbreeding depression within a population due to the increased prevalence of harmful recessive traits. Animals have evolved numerous mechanisms for avoiding close inbreeding. In some species, such as the splendid fairywren, females benefit by mating with multiple males, thus producing more offspring of higher genetic quality; some animals are capable of asexual reproduction, which results
Algae is an informal term for a large, diverse group of photosynthetic eukaryotic organisms that are not closely related, is thus polyphyletic. Including organisms ranging from unicellular microalgae genera, such as Chlorella and the diatoms, to multicellular forms, such as the giant kelp, a large brown alga which may grow up to 50 m in length. Most are aquatic and autotrophic and lack many of the distinct cell and tissue types, such as stomata and phloem, which are found in land plants; the largest and most complex marine algae are called seaweeds, while the most complex freshwater forms are the Charophyta, a division of green algae which includes, for example and the stoneworts. No definition of algae is accepted. One definition is that algae "have chlorophyll as their primary photosynthetic pigment and lack a sterile covering of cells around their reproductive cells". Although cyanobacteria are referred to as "blue-green algae", most authorities exclude all prokaryotes from the definition of algae.
Algae constitute a polyphyletic group since they do not include a common ancestor, although their plastids seem to have a single origin, from cyanobacteria, they were acquired in different ways. Green algae are examples of algae that have primary chloroplasts derived from endosymbiotic cyanobacteria. Diatoms and brown algae are examples of algae with secondary chloroplasts derived from an endosymbiotic red alga. Algae exhibit a wide range of reproductive strategies, from simple asexual cell division to complex forms of sexual reproduction. Algae lack the various structures that characterize land plants, such as the phyllids of bryophytes, rhizoids in nonvascular plants, the roots and other organs found in tracheophytes. Most are phototrophic, although some are mixotrophic, deriving energy both from photosynthesis and uptake of organic carbon either by osmotrophy, myzotrophy, or phagotrophy; some unicellular species of green algae, many golden algae, euglenids and other algae have become heterotrophs, sometimes parasitic, relying on external energy sources and have limited or no photosynthetic apparatus.
Some other heterotrophic organisms, such as the apicomplexans, are derived from cells whose ancestors possessed plastids, but are not traditionally considered as algae. Algae have photosynthetic machinery derived from cyanobacteria that produce oxygen as a by-product of photosynthesis, unlike other photosynthetic bacteria such as purple and green sulfur bacteria. Fossilized filamentous algae from the Vindhya basin have been dated back to 1.6 to 1.7 billion years ago. The singular alga retains that meaning in English; the etymology is obscure. Although some speculate that it is related to Latin algēre, "be cold", no reason is known to associate seaweed with temperature. A more source is alliga, "binding, entwining"; the Ancient Greek word for seaweed was φῦκος, which could mean either the seaweed or a red dye derived from it. The Latinization, fūcus, meant the cosmetic rouge; the etymology is uncertain, but a strong candidate has long been some word related to the Biblical פוך, "paint", a cosmetic eye-shadow used by the ancient Egyptians and other inhabitants of the eastern Mediterranean.
It could be any color: black, green, or blue. Accordingly, the modern study of marine and freshwater algae is called either phycology or algology, depending on whether the Greek or Latin root is used; the name Fucus appears in a number of taxa. The algae contain chloroplasts. Chloroplasts contain circular DNA like that in cyanobacteria and are interpreted as representing reduced endosymbiotic cyanobacteria. However, the exact origin of the chloroplasts is different among separate lineages of algae, reflecting their acquisition during different endosymbiotic events; the table below describes the composition of the three major groups of algae. Their lineage relationships are shown in the figure in the upper right. Many of these groups contain some members; some retain plastids, but not chloroplasts. Phylogeny based on plastid not nucleocytoplasmic genealogy: Linnaeus, in Species Plantarum, the starting point for modern botanical nomenclature, recognized 14 genera of algae, of which only four are considered among algae.
In Systema Naturae, Linnaeus described the genera Volvox and Corallina, a species of Acetabularia, among the animals. In 1768, Samuel Gottlieb Gmelin published the Historia Fucorum, the first work dedicated to marine algae and the first book on marine biology to use the new binomial nomenclature of Linnaeus, it included elaborate illustrations of seaweed and marine algae on folded leaves. W. H. Harvey and Lamouroux were the first to divide macroscopic algae into four divisions based on their pigmentation; this is the first use of a biochemical criterion in plant systematics. Harvey's four divisions are: red algae, brown algae, green algae, Diatomaceae. At this time, microscopic algae were discovered and reported by a different group of workers studying the Infusoria. Unlike macroalgae, which were viewed as plants, microalgae were considered animals because they are motile; the nonmotile microalgae were sometimes seen as stages of the lifecycle of plants, macroalgae, or animals. Although used as a taxonomic category in some pre-D
The Heliomonadida are a small group of heliozoan amoeboids that are unusual in possessing flagella throughout their life cycle. Genetic studies place them among the Cercozoa, a group including various other flagellates that form filose pseudopodia; this order has been placed into the new class of naked filose cercozoans called Granofilosea. There are two genera in this order: Heliomorpha, a tiny organism found in freshwater the larger Tetradimorpha, distinguished by having four rather than two flagella. Bundles of microtubules in square array, arise from a body near the flagellar bases and support the numerous axopods that project from the cell surface. Dimorphids have a single nucleus, mitochondria with tubular cristae
A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word flagellate describes a particular construction characteristic of many prokaryotes and eukaryotes and their means of motion; the term presently does not imply any specific relationship or classification of the organisms that possess flagellae. However, the term "flagellate" is included in other terms. Eukaryotic flagella are supported by microtubules in a characteristic arrangement, with nine fused pairs surrounding two central singlets; these arise from a basal body. In some flagellates, flagella direct food into a cytostome or mouth, where food is ingested. Flagella support hairs, called mastigonemes, or contain rods, their ultrastructure plays an important role in classifying eukaryotes. Among protoctists and microscopic animals, a flagellate is an organism with one or more whip-like organelles called flagella; some cells in animals may be flagellate, for instance the spermatozoa of most phyla. Flowering plants do not produce flagellate cells, but ferns, green algae, some gymnosperms and related plants do so.
Most fungi do not produce cells with flagellae, but the primitive fungal chytrids do. Many protists take the form of single-celled flagellates. Flagella are used for propulsion, they may be used to create a current that brings in food. In most such organisms, one or more flagella are located at or near the anterior of the cell, e.g. Euglena. There is one directed forwards and one trailing behind. Among animals, which are part of a group called the opisthokonts, there is a single posterior flagellum, they are from the phylum Mastigophora. They can cause diseases and are heterotrophic, they reproduce by binary fission. They spend most of their existence feeding. Many parasites that affect human health or economy are flagellates. Flagellates are the major consumers of primary and secondary production in aquatic ecosystems - consuming bacteria and other protists. An overview of the occurrence of flagellated cells in eukaryote groups, as specialized cells of multicellular organisms or as life cycle stages, is given below: Archaeplastida: most green algae, pteridophytes, some gymnosperms Stramenopiles: centric diatoms, brown algae, hyphochytrids, labyrinthulomycetes, some chrysophytes, some xanthophytes, eustigmatophytes Alveolata: some apicomplexans Rhizaria: some radiolarians, foraminiferans Cercozoa: plasmodiophoromycetes, chlorarachniophytes Amoebozoa: myxogastrids Opisthokonta: most metazoans, chytrid fungi Excavata: some acrasids In older classifications, flagellated protozoa were grouped in Flagellata, sometimes divided in Phytoflagellata and Zooflagellata.
They were sometimes grouped with Sarcodina in the group Sarcomastigophora. The autotrophic flagellates were grouped to the botanical schemes used for the corresponding algae groups; the colourless flagellates were customary grouped in three groups artificial: Protomastigineae, in which absorption of food-particles in holozoic nutrition occurs at a localised point of the cell surface at a cytostome, although many groups were saprophytes. Presently, these groups are known to be polyphyletic. In modern classifications of the protists, the principal flagellated taxa are placed in the following eukaryote groups, which include non-flagellated forms: Archaeplastida: volvocids, glaucophytes Stramenopiles: bicosoecids, opalines, most chrysophytes, part of xanthophytes, raphidophytes/chloromonads, silicoflagellates, pedinellids Alveolata: dinoflagellates, Colpodella Rhizaria Cercozoa: cercomonads, thaumatomonads, cryomonads, heliomonads/dimorphids, ebriids Amoebozoa: Multicilia, some archamoebae Opisthokonta: choanoflagellates Excavata Discoba: jakobids, euglenids, some heteroloboseans Metamonada: diplomonads, Preaxostyla/anaeromonads, parabasalids Eukaryota incertae sedis: haptophytes, kathablepharids, collodictyonids/diphylleids and about a hundred generaAlthough the taxonomic group Flagellata was abandoned, the term "flagellate" is still used as the description of a level of organization and as an ecological functional group.
Another term used is "monadoid", from monad. as