1.
Cell (biology)
–
The cell is the basic structural, functional, and biological unit of all known living organisms. A cell is the smallest unit of life that can replicate independently, the study of cells is called cell biology. Cells consist of cytoplasm enclosed within a membrane, which contains many such as proteins. Organisms can be classified as unicellular or multicellular, while the number of cells in plants and animals varies from species to species, humans contain more than 10 trillion cells. Most plant and animal cells are only under a microscope. The cell was discovered by Robert Hooke in 1665, who named the unit for its resemblance to cells inhabited by Christian monks in a monastery. Cells emerged on Earth at least 3.5 billion years ago, Cells are of two types, eukaryotic, which contain a nucleus, and prokaryotic, which do not. Prokaryotes are single-celled organisms, while eukaryotes can be either single-celled or multicellular, prokaryotic cells were the first form of life on Earth, characterised by having vital biological processes including cell signaling and being self-sustaining. They are simpler and smaller than eukaryotic cells, and lack membrane-bound organelles such as the nucleus, prokaryotes include two of the domains of life, bacteria and archaea. The DNA of a prokaryotic cell consists of a chromosome that is in direct contact with the cytoplasm. The nuclear region in the cytoplasm is called the nucleoid, most prokaryotes are the smallest of all organisms ranging from 0.5 to 2.0 µm in diameter. Though most prokaryotes have both a cell membrane and a wall, there are exceptions such as Mycoplasma and Thermoplasma which only possess the cell membrane layer. The envelope gives rigidity to the cell and separates the interior of the cell from its environment, the cell wall consists of peptidoglycan in bacteria, and acts as an additional barrier against exterior forces. It also prevents the cell from expanding and bursting from osmotic pressure due to a hypotonic environment, some eukaryotic cells also have a cell wall. Inside the cell is the region that contains the genome, ribosomes. The genetic material is found in the cytoplasm. Prokaryotes can carry extrachromosomal DNA elements called plasmids, which are usually circular, linear bacterial plasmids have been identified in several species of spirochete bacteria, including members of the genus Borrelia notably Borrelia burgdorferi, which causes Lyme disease. Though not forming a nucleus, the DNA is condensed in a nucleoid, plasmids encode additional genes, such as antibiotic resistance genes
2.
Mammal
–
Mammals are any vertebrates within the class Mammalia, a clade of endothermic amniotes distinguished from reptiles by the possession of a neocortex, hair, three middle ear bones and mammary glands. All female mammals nurse their young with milk, secreted from the mammary glands, Mammals include the largest animals on the planet, the great whales. The basic body type is a quadruped, but some mammals are adapted for life at sea, in the air, in trees. The largest group of mammals, the placentals, have a placenta, Mammals range in size from the 30–40 mm bumblebee bat to the 30-meter blue whale. With the exception of the five species of monotreme, all modern mammals give birth to live young, most mammals, including the six most species-rich orders, belong to the placental group. The largest orders are the rodents, bats and Soricomorpha, the next three biggest orders, depending on the biological classification scheme used, are the Primates, the Cetartiodactyla, and the Carnivora. Living mammals are divided into the Yinotheria and Theriiformes There are around 5450 species of mammal, in some classifications, extant mammals are divided into two subclasses, the Prototheria, that is, the order Monotremata, and the Theria, or the infraclasses Metatheria and Eutheria. The marsupials constitute the group of the Metatheria, and include all living metatherians as well as many extinct ones. Much of the changes reflect the advances of cladistic analysis and molecular genetics, findings from molecular genetics, for example, have prompted adopting new groups, such as the Afrotheria, and abandoning traditional groups, such as the Insectivora. The mammals represent the only living Synapsida, which together with the Sauropsida form the Amniota clade, the early synapsid mammalian ancestors were sphenacodont pelycosaurs, a group that produced the non-mammalian Dimetrodon. At the end of the Carboniferous period, this group diverged from the line that led to todays reptiles. Some mammals are intelligent, with some possessing large brains, self-awareness, Mammals can communicate and vocalize in several different ways, including the production of ultrasound, scent-marking, alarm signals, singing, and echolocation. Mammals can organize themselves into fission-fusion societies, harems, and hierarchies, most mammals are polygynous, but some can be monogamous or polyandrous. They provided, and continue to provide, power for transport and agriculture, as well as commodities such as meat, dairy products, wool. Mammals are hunted or raced for sport, and are used as model organisms in science, Mammals have been depicted in art since Palaeolithic times, and appear in literature, film, mythology, and religion. Defaunation of mammals is primarily driven by anthropogenic factors, such as poaching and habitat destruction, Mammal classification has been through several iterations since Carl Linnaeus initially defined the class. No classification system is accepted, McKenna & Bell and Wilson & Reader provide useful recent compendiums. Though field work gradually made Simpsons classification outdated, it remains the closest thing to a classification of mammals
3.
Plant
–
Plants are mainly multicellular, predominantly photosynthetic eukaryotes of the kingdom Plantae. The term is generally limited to the green plants, which form an unranked clade Viridiplantae. This includes the plants, conifers and other gymnosperms, ferns, clubmosses, hornworts, liverworts, mosses and the green algae. Green plants have cell walls containing cellulose and obtain most of their energy from sunlight via photosynthesis by primary chloroplasts and their chloroplasts contain chlorophylls a and b, which gives them their green color. Some plants are parasitic and have lost the ability to produce amounts of chlorophyll or to photosynthesize. Plants are characterized by sexual reproduction and alternation of generations, although reproduction is also common. There are about 300–315 thousand species of plants, of which the great majority, green plants provide most of the worlds molecular oxygen and are the basis of most of Earths ecologies, especially on land. Plants that produce grains, fruits and vegetables form humankinds basic foodstuffs, Plants play many roles in culture. They are used as ornaments and, until recently and in variety, they have served as the source of most medicines. The scientific study of plants is known as botany, a branch of biology, Plants are one of the two groups into which all living things were traditionally divided, the other is animals. The division goes back at least as far as Aristotle, who distinguished between plants, which generally do not move, and animals, which often are mobile to catch their food. Much later, when Linnaeus created the basis of the system of scientific classification. Since then, it has become clear that the plant kingdom as originally defined included several unrelated groups, however, these organisms are still often considered plants, particularly in popular contexts. When the name Plantae or plant is applied to a group of organisms or taxon. The evolutionary history of plants is not yet settled. Those which have been called plants are in bold, the way in which the groups of green algae are combined and named varies considerably between authors. Algae comprise several different groups of organisms which produce energy through photosynthesis, most conspicuous among the algae are the seaweeds, multicellular algae that may roughly resemble land plants, but are classified among the brown, red and green algae. Each of these groups also includes various microscopic and single-celled organisms
4.
Granulocyte
–
Granulocytes are a category of white blood cells characterized by the presence of granules in their cytoplasm. They are also called polymorphonuclear leukocytes because of the shapes of the nucleus. This distinguishes them from the mononuclear agranulocytes, in common parlance, the term polymorphonuclear leukocyte often refers specifically to neutrophil granulocytes, the most abundant of the granulocytes, the other types have lower numbers. Granulocytes are produced via granulopoiesis in the bone marrow, neutrophils are normally found in the bloodstream and are the most abundant type of phagocyte, constituting 50% to 60% of the total circulating white blood cells. One litre of blood contains about five billion neutrophils, which are about 12–15 micrometers in diameter. Once neutrophils have received the signals, it takes them about thirty minutes to leave the blood. Neutrophils do not return to the blood, they turn into pus cells, mature neutrophils are smaller than monocytes, and have a segmented nucleus with several sections, each section is connected by chromatin filaments. Neutrophils do not normally exit the bone marrow until maturity, neutrophils have three strategies for directly attacking micro-organisms, phagocytosis, release of soluble anti-microbials, and generation of neutrophil extracellular traps. Neutrophils are professional phagocytes, they are ferocious eaters and rapidly engulf invaders coated with antibodies and complement, the intracellular granules of the human neutrophil have long been recognized for their protein-destroying and bactericidal properties. Neutrophils can secrete products that stimulate monocytes and macrophages, these secretions increase phagocytosis, neutrophils have two types of granules, primary granules and secondary granules. In addition, secretions from the granules of neutrophils stimulate the phagocytosis of IgG antibody-coated bacteria. The secondary granules contain compounds that are involved in the formation of oxygen compounds, lysozyme. Neutrophil extracellular traps comprise a web of fibers composed of chromatin and serine proteases that trap, trapping of bacteria is a particularly important role for NETs in sepsis, where NET are formed within blood vessels. Eosinophils also have kidney-shaped lobed nuclei, the number of granules in an eosinophil can vary because they have a tendency to degranulate while in the blood stream. A polypeptide called interleukin-5 interacts with eosinophils and causes them to grow and differentiate, basophils are one of the least abundant cells in bone marrow and blood. Like neutrophils and eosinophils, they have lobed nuclei, however, basophils have receptors that can bind to IgE, IgG, complement, and histamine. The cytoplasm of basophils contains an amount of granules, these granules are usually numerous enough to partially conceal the nucleus. Granule contents of basophils are abundant with histamine, heparin, chondroitin sulfate, peroxidase, platelet-activating factor, when an infection occurs, mature basophils will be released from the bone marrow and travel to the site of infection
5.
Slime mold
–
Slime molds were formerly classified as fungi but are no longer considered part of that kingdom. Although not related to one another, they are sometimes grouped for convenience within the paraphyletic group referred to as kingdom Protista. More than 500 species of slime mold occur all over the world and their common name refers to part of some of these organisms life cycles where they can appear as gelatinous slime. This is mostly seen with the myxogastria, which are the only macroscopic slime molds, most slime molds are smaller than a few centimeters, but some species may reach sizes of up to several square meters and masses of up to 30 grams. Many slime molds, mainly the cellular slime molds, do not spend most of their time in this state, as long as food is abundant, these slime molds exist as single-celled organisms. When food is in supply, many of these single-celled organisms will congregate. In this state they are sensitive to chemicals and can detect food sources. They feed on microorganisms that live in any type of plant material. They contribute to the decomposition of dead vegetation, and feed on bacteria, yeasts, for this reason, slime molds are usually found in soil, lawns, and on the forest floor, commonly on deciduous logs. However, in areas they are also common on inflorescences, fruits. In urban areas, they are found on mulch or even in the mold in gutters. Slime molds, as a group, are polyphyletic and they were originally represented by the subkingdom Gymnomycota in the Fungi kingdom and included the defunct phyla Myxomycota, Acrasiomycota and Labyrinthulomycota. Today, slime molds have been divided among several supergroups, none of which is included in the kingdom Fungi, Slime molds can generally be divided into two main groups. A plasmodial slime mold is enclosed within a single membrane without walls and is one large cell and this supercell is essentially a bag of cytoplasm containing thousands of individual nuclei. By contrast, cellular slime molds spend most of their lives as individual unicellular protists, in more strict terms, slime molds comprise the mycetozoan group of the amoebozoa. Mycetozoa include the three groups, Myxogastria or myxomycetes, syncytial or plasmodial slime molds Dictyosteliida or dictyostelids, cellular slime molds. Even at this level of classification there are conflicts to be resolved, recent molecular evidence shows that, while the first two groups are likely to be monophyletic, the protosteloids are likely to be polyphyletic. For this reason, scientists are trying to understand the relationships among these three groups
6.
Placenta
–
The placenta provides oxygen and nutrients to growing babies and removes waste products from the babys blood. The placenta attaches to the wall of the uterus, and the umbilical cord develops from the placenta. The umbilical cord is what connects the mother and the baby, Placentas are a defining characteristic of placental mammals, but are also found in some non-mammals with varying levels of development. The homology of structures in various viviparous organisms is debatable. The classical plural is placentae, but the form placentas is common in modern English, prototherial and metatherial mammals produce a choriovitelline placenta that, while connected to the uterine wall, provides nutrients mainly derived from the egg sac. In humans, the placenta averages 22 cm in length and 2–2.5 cm in thickness, with the center being the thickest, and it typically weighs approximately 500 grams. It has a dark reddish-blue or crimson color and it connects to the fetus by an umbilical cord of approximately 55–60 cm in length, which contains two umbilical arteries and one umbilical vein. The umbilical cord inserts into the chorionic plate, vessels branch out over the surface of the placenta and further divide to form a network covered by a thin layer of cells. This results in the formation of villous tree structures, on the maternal side, these villous tree structures are grouped into lobules called cotyledons. In humans, the placenta usually has a shape. The placental flora more closely resembles that of the oral microbiome than either the vaginal or rectal microbiome, in non-human animals, part of the microbiome is passed onto offspring even before the offspring are born. Bacteriologists assume that the same holds true for humans. The placenta begins to develop upon implantation of the blastocyst into the maternal endometrium, the outer layer of the blastocyst becomes the trophoblast, which forms the outer layer of the placenta. This outer layer is divided into two layers, the underlying cytotrophoblast layer and the overlying syncytiotrophoblast layer. The syncytiotrophoblast is a continuous cell layer that covers the surface of the placenta. It forms as a result of differentiation and fusion of the underlying cytotrophoblast cells, the syncytiotrophoblast, thereby contributes to the barrier function of the placenta. Development of the blood supply to the placenta is complete by the end of the first trimester of pregnancy. In preparation for implantation of the blastocyst, the uterine endometrium undergoes decidualisation, spiral arteries in decidua are remodeled so that they become less convoluted and their diameter is increased
7.
Mold
–
A mold or mould is a fungus that grows in the form of multicellular filaments called hyphae. In contrast, fungi that can adopt a single-celled growth habit are called yeasts, molds are a large and taxonomically diverse number of fungal species in which the growth of hyphae results in discoloration and a fuzzy appearance, especially on food. The network of these tubular branching hyphae, called a mycelium, is considered a single organism, the hyphae are generally transparent, so the mycelium appears like very fine, fluffy white threads over the surface. Cross-walls may delimit connected compartments along the hyphae, each containing one or multiple, the dusty texture of many molds is caused by profuse production of asexual spores formed by differentiation at the ends of hyphae. The mode of formation and shape of spores is traditionally used to classify molds. Many of these spores are colored, making the much more obvious to the human eye at this stage in its life-cycle. Molds are considered to be microbes and do not form a taxonomic or phylogenetic grouping. In the past, most molds were classified within the Deuteromycota, molds cause biodegradation of natural materials, which can be unwanted when it becomes food spoilage or damage to property. They also play important roles in biotechnology and food science in the production of foods, beverages, antibiotics, pharmaceuticals. There are thousands of species of molds, which have diverse life-styles including saprotrophs, mesophiles, psychrophiles and thermophiles. They all require moisture for growth and some live in aquatic environments, like all fungi, molds derive energy not through photosynthesis but from the organic matter on which they live, utilising heterotrophy. Typically, molds secrete hydrolytic enzymes, mainly from the hyphal tips and these enzymes degrade complex biopolymers such as starch, cellulose and lignin into simpler substances which can be absorbed by the hyphae. In this way molds play a role in causing decomposition of organic material. Many molds also synthesise mycotoxins and siderophores which, together with lytic enzymes, molds can also grow on stored food for animals and humans, making the food unpalatable or toxic and are thus a major source of food losses and illness. Many strategies for food preservation are to prevent or slow growth as well as growth of other microbes. Molds reproduce by producing large numbers of spores, which may contain a single nucleus or be multinucleate. Mold spores can be asexual or sexual, many species can produce both types, other mold spores have slimy sheaths and are more suited to water dispersal. Mold spores are spherical or ovoid single cells, but can be multicellular
8.
Myxogastria
–
Myxogastria/Myxogastrea or Myxomycetes, is a grouping of slime molds that contains 5 orders,14 families,62 genera and 888 species. They are colloquially known as the plasmodial or acellular slime moulds, all species pass through several, very different morphologic phases, such as microscopic individual cells, slimy amorphous organisms visible with the naked eye and conspicuously shaped fruit bodies. Although they are monocellular, they can reach immense widths and weights, in extreme cases they can be up to 1 metre across and weigh up to 20 kilograms. The class Myxogastria is distributed worldwide, but it is common in temperate regions where it has a higher biodiversity than in polar regions. They are mainly found in forests, but also in extreme regions such as deserts. They also occur on the bark of trees, sometimes high in the canopy and these are known as corticolous myxomycetes. The Latin name Myxomycota comes from the Ancient Greek words μύξα, which means mucus, and μύκης, the name Myxogastria was introduced in 1970 by Lindsay Shepherd Olive to describe the family Myxogastridae, which was introduced in 1899 by Thomas Huston Macbride. Swedish mycologist Elias Magnus Fries described numerous slime moulds as Myxogasteres in 1829, species in the class Myxomycota are colloquially known as plasmodial or acellular slime moulds. Some consider the Myxomycota to be a kingdom, with an unsettled phylogeny because of conflicting molecular. The relations among Myxogastrid orders are as yet unclear, the continuous classification of new taxa reveals that the class is not fully described. The class comprises around 900 to 1000 species, according to a 2000 inquiry, there were 1012 officially accepted taxa, including 866 on species level. Another study in 2007 stated a number of more than 1000, in which the Myxogastria comprised the biggest group of slime moulds, on the basis of sequenced environmental samples it is estimated that the group has between 1200 and 1500 species, more than previously estimated. In the past authors have tried to describe a new taxon based on a small number of examples. For example, Squamuloderma nullifila is actually a species from the genus Didymium, the following classification is based on Adl et al. 2005, while the classes and further divisions on Dykstra and Keller 2000, the sister taxon is the subclass Dictyostelia. Together with the Protostelia they formed the taxon of the Eumycetozoae, molecular genetical studies confirm and stabilise this classification. The most basal group is Echinosteliida, other groups further contain two superclades, which are morphologically definable by spore colour. The spores of Myxogastria are haploid, mainly round and measure between 5 µm and 20 µm, rarely up to 24 µm in diameter and their surface is generally reticular, sharp, warty or spiky and very rarely smooth
9.
Plasmodium
–
Plasmodium is a genus of parasitic alveolates, many of which cause malaria in their hosts. The parasite always has two hosts in its cycle, a Dipteran insect host and a vertebrate host. Sexual reproduction always occurs in the insect, making it the definitive host, the life-cycles of Plasmodium species involve several different stages both in the insect and the vertebrate host. These stages include sporozoites, which are injected by the vector into the vertebrate hosts blood. Sporozoites infect the host liver, giving rise to merozoites and hypnozoites and these move into the blood where they infect red blood cells. In the red cells, the parasites can either form more merozoites to infect more red blood cells. In the insect host, gametocytes merge to sexually reproduce, after sexual reproduction, parasites grow into new sporozoites, which move to the insects salivary glands, from which they can infect a vertebrate host bitten by the insect. The genus Plasmodium was first described in 1885 and it now contains about 200 species, which are spread across the world where both the insect and vertebrate hosts are present. Five species regularly infect humans, while many others infect birds, reptiles, rodents, Plasmodium was first identified when Charles Louis Alphonse Laveran described parasites in the blood of malaria patients in 1880. He named the parasite Oscillaria malariae, the fact that several species may be involved in causing different forms of malaria was first recognized by Camillo Golgi in 1886. Soon thereafter, Giovanni Batista Grassi and Raimondo Filetti named the parasites causing two different types of human malaria Plasmodium vivax and Plasmodium malariae, in 1897, William Welch identified and named Plasmodium falciparum. This was followed by the recognition of the two species of Plasmodium which infect humans, Plasmodium ovale and Plasmodium knowlesi. The contribution of insect hosts to the Plasmodium life cycle was described in 1897 by Ronald Ross and in 1899 by Giovanni Batista Grassi, Amico Bignami, the life cycle of Plasmodium involves several distinct stages in the insect and vertebrate hosts. In infected mosquitoes, parasites in the gland are called sporozoites. When the mosquito bites a vertebrate host, sporozoites are injected into the host with the saliva, from there, the sporozoites enter the bloodstream and are transported to the liver, where they invade and replicate within hepatocytes. At this point, some species of Plasmodium can form a dormant stage called a hypnozoite which can remain in the liver for many years. The parasites that emerge from infected hepatocytes are called merozoites, within the red blood cells, the merozoites grow first to a ring-shaped form and then to a larger form called a trophozoite. Trophozoites then mature to schizonts which divide several times to produce new merozoites, the infected red blood cell eventually bursts, allowing the new merozoites to travel within the bloodstream to infect new red blood cells
10.
Parasitism
–
In biology/ecology, parasitism is a non-mutual relationship between species, where one species, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred primarily to organisms visible to the naked eye, Parasites can be microparasites, which are typically smaller, such as protozoa, viruses, and bacteria. Examples of parasites include the plants mistletoe and cuscuta, and animals such as hookworms, unlike predators, parasites typically do not kill their host, are generally much smaller than their host, and will often live in or on their host for an extended period. Both are special cases of consumer-resource interactions, Parasites show a high degree of specialization, and reproduce at a faster rate than their hosts. Classic examples of parasitism include interactions between vertebrate hosts and tapeworms, flukes, the Plasmodium species, and fleas, parasitism differs from the parasitoid relationship in that parasitoids generally kill their hosts. Parasites reduce host biological fitness by general or specialized pathology, such as parasitic castration and impairment of secondary sex characteristics, Parasites increase their own fitness by exploiting hosts for resources necessary for their survival, e. g. food, water, heat, habitat, and transmission. Although parasitism applies unambiguously to many cases, it is part of a continuum of types of interactions between species, rather than an exclusive category, in many cases, it is difficult to demonstrate harm to the host. In others, there may be no apparent specialization on the part of the parasite, coined in English in 1611, the word parasitism comes from the Greek παρά + σιτισμός feeding, fattening. Parasites are classified based on their interactions with their hosts and on their life cycles, an obligate parasite is totally dependent on the host to complete its life cycle, while a facultative parasite is not. A direct parasite has one host while an indirect parasite has multiple hosts. For indirect parasites, there always be a definitive host. Parasites that live on the outside of the host, either on the skin or the outgrowths of the skin, are called ectoparasites and those that live inside the host are called endoparasites. Endoparasites can exist in one of two forms, intercellular parasites or intracellular parasites, intracellular parasites, such as protozoa, bacteria or viruses, tend to rely on a third organism, which is generally known as the carrier or vector. The vector does the job of transmitting them to the host, an example of this interaction is the transmission of malaria, caused by a protozoan of the genus Plasmodium, to humans by the bite of an anopheline mosquito. Those parasites living in a position, being half-ectoparasites and half-endoparasites, are called mesoparasites. An epiparasite is one that feeds on another parasite and this relationship is also sometimes referred to as hyperparasitism, exemplified by a protozoan living in the digestive tract of a flea living on a dog. Social parasites take advantage of interactions between members of social organisms such as ants, termites, and bumblebees, an extreme example of social parasitism is the ant species of Tetramorium inquilinum of the Alps, which spend their whole lives on the back of Tetramorium host ants. With tiny and deprecated bodies they have evolved for one single task, if they fall off, they most likely would not have the strength to climb back on top of another ant, and eventually they will die
11.
Eukaryote
–
A eukaryote is any organism whose cells contain a nucleus and other organelles enclosed within membranes. Eukaryotes belong to the taxon Eukarya or Eukaryota, the presence of a nucleus gives eukaryotes their name, which comes from the Greek εὖ and κάρυον. Eukaryotic cells also contain other membrane-bound organelles such as mitochondria and the Golgi apparatus, in addition, plants and algae contain chloroplasts. Eukaryotic organisms may be unicellular or multicellular, only eukaryotes form multicellular organisms consisting of many kinds of tissue made up of different cell types. Eukaryotes can reproduce asexually through mitosis and sexually through meiosis and gamete fusion. In mitosis, one cell divides to produce two identical cells. In meiosis, DNA replication is followed by two rounds of division to produce four daughter cells each with half the number of chromosomes as the original parent cell. These act as sex cells resulting from genetic recombination during meiosis, the domain Eukaryota appears to be monophyletic, and so makes up one of the three domains of life. The two other domains, Bacteria and Archaea, are prokaryotes and have none of the above features, eukaryotes represent a tiny minority of all living things. However, due to their larger size, eukaryotes collective worldwide biomass is estimated at about equal to that of prokaryotes. Eukaryotes first developed approximately 1. 6–2.1 billion years ago, in 1905 and 1910, the Russian biologist Konstantin Mereschkowsky argued three things about the origin of nucleated cells. Firstly, plastids were reduced cyanobacteria in a symbiosis with a non-photosynthetic host, secondly, the host had earlier in evolution formed by symbiosis between an amoeba-like host and a bacteria-like cell that formed the nucleus. Thirdly, plants inherited photosynthesis from cyanobacteria, the split between the prokaryotes and eukaryotes was introduced in the 1960s. The concept of the eukaryote has been attributed to the French biologist Edouard Chatton, the terms prokaryote and eukaryote were more definitively reintroduced by the Canadian microbiologist Roger Stanier and the Dutch-American microbiologist C. B. van Niel in 1962. In his 1938 work Titres et Travaux Scientifiques, Chatton had proposed the two terms, calling the bacteria prokaryotes and organisms with nuclei in their cells eukaryotes. However he mentioned this in one paragraph, and the idea was effectively ignored until Chattons statement was rediscovered by Stanier. In 1967, Lynn Margulis provided microbiological evidence for endosymbiosis as the origin of chloroplasts and mitochondria in cells in her paper. In the 1970s, Carl Woese explored microbial phylogenetics, studying variations in 16S ribosomal RNA and this helped to uncover the origin of the eukaryotes and the symbiogenesis of two important eukaryote organelles, mitochondria and chloroplasts
12.
Douglas fir
–
Pseudotsuga menziesii, commonly known as Douglas fir or Douglas-fir, is an evergreen conifer species native to western North America. The common name honors David Douglas, a Scottish botanist and collector who first reported the extraordinary nature, the common name is misleading since it is not a true fir, i. e. not a member of the genus Abies. For this reason the name is written as Douglas-fir. The specific epithet, menziesii, is after Archibald Menzies, a Scottish physician, Menzies first documented the tree on Vancouver Island in 1791. Colloquially, the species is known simply as Doug-fir or as Douglas pine. One Coast Salish name for the tree, used in the Halkomelem language, is lá, one variety, coast Douglas fir, grows in the coastal regions, from west-central British Columbia southward to central California. In Oregon and Washington, its range is continuous from the edge of the Cascades west to the Pacific Coast Ranges. In California, it is found in the Klamath and California Coast Ranges as far south as the Santa Lucia Range, in the Sierra Nevada, it ranges as far south as the Yosemite region. It occurs from sea level along the coast to 1,800 m above sea level in the mountains of California. Further inland, coast Douglas fir is replaced by another variety, mexican Douglas fir, which ranges as far south as Oaxaca, is often considered a variety of P. menziesii. Coast Douglas fir is currently the second-tallest conifer in the world. Extant coast Douglas fir trees 60–75 m or more in height and 1. 5–2 m in diameter are common in old growth stands, Douglas firs commonly live more than 500 years and occasionally more than 1,000 years. The bark on trees is thin, smooth, and gray. On mature trees, it is thick and corky, the shoots are brown to olive-green, turning gray-brown with age, smooth, though not as smooth as fir shoots, and finely pubescent with short, dark hairs. The buds are a distinctive, narrow, conic shape, 4–8 mm long. Unlike the Rocky Mountain Douglas fir, coast Douglas fir foliage has a noticeable sweet fruity-resinous scent, the mature female seed cones are pendulous, 5–8 cm long, 2–3 cm wide when closed, opening to a 4 cm width. They are produced in spring, green at first, maturing orange-brown in the autumn 6–7 months later, the seeds are 5–6 mm long and 3–4 mm wide, with a 12–15-mm wing. The male cones are 2–3 cm long, dispersing yellow pollen in spring, in forest conditions, old individuals typically have a narrow, cylindric crown beginning 20–40 m above a branch-free trunk
