Life on Earth Fossil range: Late Hadean - Recent
These Escherichia coli cells provide an example of a prokaryotic microorganism
Scientific classification
(unranked) Life on Earth (Gaeabionta)
Domains and Kingdoms
Nanobes ? Acytota **? Cytota Bacteria * Neomura Archaea Eukaryota Bikonta Apusozoa Rhizaria Excavata Archaeplastida Rhodophyta Glaucophyta Plantae Heterokontophyta Haptophyta Cryptophyta Alveolata Unikonta Amoebozoa Opisthokonta Choanozoa Fungi Animalia

An ericoid mycorrhizal fungus

In biology, an organism is an individual living system (such as animal, plant, fungus, or micro-organism). Foundations of modern biology There are five unifying principles Life is a state that distinguishes Organisms from non-living objects such as non-life and dead organisms being manifested by growth through Metabolism In at least some form, all organisms are capable of reacting to stimuli, reproduction, growth and maintenance as a stable whole (after FAO^[1]). An organism may be unicellular or made up, as in humans, of many billions of cells grouped into specialized tissues and organs. A microorganism (also spelled micro organism or micro-organism and also called a microbe) is an Organism that is Microscopic (usually The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called Tissue is a cellular organizational level intermediate between cells and a complete organism In Biology, an organ ( Latin: organum, "instrument tool" from Greek όργανον - organon "organ instrument The phrase complex organism describes any organism with more than one cell. Multicellular organisms are Organisms consisting of more than one cell, and having Differentiated cells that perform specialized functions The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called

The term "organism" (Greek (οργανισμός - organismos, from Ancient Greek όργανον - organon "organ, instrument, tool") first appeared in the English language in 1701 and took on its current definition by 1834 (Oxford English Dictionary). Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly The Ancient Greek language is the historical stage in the development of the Hellenic language family spanning the Archaic (c

Organisms may be divided into the prokaryotic and eukaryotic groups. The prokaryotes (proʊˈkærioʊts singular prokaryote /proʊˈkæriət/ are a group of Organisms that lack a Cell nucleus (= karyon or any other Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex The prokaryotes represent two separate domains, the Bacteria and Archaea. The three-domain system is a Biological classification introduced by Carl Woese in 1990 that divides cellular life forms into Archaea, The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have ^[2] All fungi, animals and plants are eukaryotes. A fungus (ˈfʌŋgəs is a eukaryotic Organism that is a member of the kingdom Fungi (ˈfʌndʒaɪ Plants are living Organisms belonging to the kingdom Plantae.

The word "organism" may broadly be defined as an assembly of molecules that function as a more or less stable whole and has the properties of life. However, many sources propose definitions that exclude viruses and theoretically-possible man-made non-organic life forms. A virus (from the Latin virus meaning Toxin or Poison) is a sub-microscopic infectious agent that is unable Alternative biochemistry is the speculative Biochemistry of alien Life forms that differ radically from those on Earth. ^[3] Viruses are dependent on the biochemical machinery of a host cell for reproduction.

Chambers Online Reference provides a broad definition: "any living structure, such as a plant, animal, fungus or bacterium, capable of growth and reproduction"^[4]. The tenth edition of The Chambers Dictionary of the English language was published in 2006 by Chambers Harrap Publishers.

In multicellular life the word "organism" usually describes the whole hierarchical assemblage of systems (for example circulatory, digestive, or reproductive) themselves collections of organs; these are, in turn, collections of tissues, which are themselves made of cells. This is an article about the rock music band "Circulatory System" Digestion is the breaking down of chemicals in the body into a form that can be absorbed The reproductive system is a system of organs within an Organism which work together for the purpose of Reproduction. In Biology, an organ ( Latin: organum, "instrument tool" from Greek όργανον - organon "organ instrument The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called In some plants and the nematode Caenorhabditis elegans, individual cells are totipotent. The nematodes or roundworms ( Phylum Nematoda from Greek (nema "thread" + -ode "like" are one of the most common Caenorhabditis elegans (ˌsiːnoʊræbˈdaɪtɪs ˈɛlɪgænz is a free-living Nematode (roundworm about 1  mm in length which Totipotency is the ability of a single cell to divide and produce all the differentiated cells in an Organism, including extraembryonic tissues

A polypores mushroom has parasitic relationship with this Birch Tree

Herpes simplex virus

Viruses

Viruses are not typically considered to be organisms because they are incapable of "independent" reproduction or metabolism. Polypores are a group of tough leathery poroid Mushrooms similar to Boletes, but typically lacking a distinct stalk A mushroom is the fleshy Spore -bearing Fruiting body of a Fungus, typically produced above ground on soil or on its food source Parasitism is a type of symbiotic relationship between Organisms of different Species. Birch is the name of any Tree of the genus Betula ( Bé-tu-la) in the family Betulaceae, closely related to the A virus (from the Latin virus meaning Toxin or Poison) is a sub-microscopic infectious agent that is unable Reproduction is the Biological process by which new individual Organisms are produced Metabolism is the set of Chemical reactions that occur in living Organisms in order to maintain Life. This controversy is problematic, though, since some parasites and endosymbionts are also incapable of independent life. Parasitism is a type of symbiotic relationship between Organisms of different Species. An endosymbiont is any Organism that lives within the body or cells of another organism i Although viruses have enzymes and molecules characteristic of living organisms, they are incapable of reproducing outside a host cell and most of their metabolic processes require a host and its 'genetic machinery. Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called '

Superorganism

Main article: Superorganism

A superorganism is an organism consisting of many organisms. A superorganism is an Organism consisting of many organisms This is usually meant to be a Social unit of eusocial animals where Division of labour This is usually meant to be a social unit of eusocial animals, where division of labour is highly specialized and where individuals are not able to survive by themselves for extended periods of time. Eusociality ( Greek eu: "good" + "social" is a term used for the highest level of social organization in a hierarchical classification Division of labour or specialization is the specialization of cooperative labour in specific circumscribed tasks and roles intended to increase the Productivity Ants are the most well known example of such a superorganism. Ants are social Insects of the family Formicidae and along with the related families of Wasps and Bees belong to the order Thermoregulation, a feature usually exhibited by individual organisms, does not occur in individuals or small groups of honeybees of the species Apis mellifera. Thermoregulation is the ability of an Organism to keep its body temperature within certain boundaries even when temperature surrounding is very different This article refers collectively to all true honey bees for the "common" domesticated honey bee see European honey bee Honey bees When these bees pack together in clusters of between 5000 and 40000, the colony can thermoregulate. ^[5] James Lovelock, with his "Gaia Theory" has paralleled the work of Vladimir Vernadsky, who suggested the whole of the biosphere in some respects can be considered as a superorganism. Dr James Ephraim Lovelock, CH, CBE, FRS (born 26 July 1919) is an independent scientist author researcher environmentalist and The Gaia hypothesis is an ecological Hypothesis proposing that the Biosphere and the physical components of the Earth ( Atmosphere Vladimir Ivanovich Vernadsky (Володимир Іванович Вернадський/Владимир Иванович Вернадский ( - January 6 1945 The biosphere is the broadest level of ecological study the global sum of all Ecosystems.

A sea sponge is a very simple type of multicellular organism

The concept of superorganism is under dispute, as many biologists maintain that in order for a social unit to be considered an organism by itself, the individuals should be in permanent physical connection to each other, and its evolution should be governed by selection to the whole society instead of individuals. The sponges or poriferans (from Latin porus "pore" and ferre "to bear" are Animals Multicellular organisms are Organisms consisting of more than one cell, and having Differentiated cells that perform specialized functions Foundations of modern biology There are five unifying principles eVolution is the third Album by eLDee, it was due to be released in 2008 While it's generally accepted that the society of eusocial animals is a unit of natural selection to at least some extent, most evolutionists claim that the individuals are still the primary units of selection. Natural selection is the process by which favorable Heritable traits become more common in successive Generations of a Population of In the Creation-evolution controversy, those who accept the Scientific theory of biological Evolution by Natural selection or Genetic drift are

The question remains "What is to be considered the individual?". Darwinians like Richard Dawkins suggest that the individual selected is the "Selfish Gene". Darwinism is a term used for various different movements or concepts related to a greater or lesser extent to Charles Darwin 's work on Evolution. Clinton Richard Dawkins, FRS, FRSL (born 26 March 1941 is a British ethologist, evolutionary biologist, and Popular science Others believe it is the whole genome of an organism. E.O. Wilson has shown that with ant-colonies and other social insects it is the breeding entity of the colony that is selected, and not its individual members. Edward Osborne Wilson (born June 10, 1929) is an American biologist researcher ( Sociobiology, Biodiversity) theorist ( Insects ( Class Insecta) are a major group of Arthropods and the most diverse group of Animals on the Earth with over a million described This could apply to the bacterial members of a stromatolite, which, because of genetic sharing, in some way comprise a single gene pool. Stromatolites (from Greek στρώμα strōma, mattress bed stratum and λιθος lithos, rock are layered accretionary Structures formed in In Population genetics, a gene pool is the complete set of unique Alleles in a Species or Population. Gaian theorists like Lynn Margulis would argue this applies equally to the symbiogenesis of the bacterial underpinnings of the whole of the Earth. Lynn Margulis (born March 5, 1938) is an American Biologist and University Professor in the Department of Geosciences Symbiogenesis is the merging of two separate organisms to form a single new organism

It would appear, from computer simulations like Daisyworld that biological selection occurs at multiple levels simultaneously. Simulation is the imitation of some real thing state of affairs or process Daisyworld, a Computer simulation, is a hypothetical world Orbiting a Sun whose Temperature is slowly increasing in the simulation Natural selection is the process by which favorable Heritable traits become more common in successive Generations of a Population of

It is also argued that humans are actually a superorganism that includes microorganisms such as bacteria. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have It is estimated that "the human intestinal microbiota is composed of 10¹³ to 10¹⁴ microorganisms whose collective genome ("microbiome") contains at least 100 times as many genes as our own[. In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby . . ] Our microbiome has significantly enriched metabolism of glycans, amino acids, and xenobiotics; methanogenesis; and 2-methyl-D-erythritol 4-phosphate pathway–mediated biosynthesis of vitamins and isoprenoids. The term glycan refers to a Polysaccharide or Oligosaccharide. In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this A xenobiotic is a Chemical which is found in an Organism but which is not normally produced or expected to be present in it Methanogenesis or biomethanation is the formation of Methane by Microbes known as Methanogens Organisms capable of producing methane have been The terpenoids, sometimes referred to as isoprenoids, are a large and diverse class of naturally-occurring organic chemicals similar to Terpenes derived Thus, humans are superorganisms whose metabolism represents an amalgamation of microbial and human attributes. " ^[6]. An NIH-coordinated and -funded effort is currently in progress to characterize the human microbiome. "NIH" redirects here For other meanings of NIH see NIH (disambiguation. The Human microbiome project (HMP is a National Institutes of Health initiative with the goal of identifying and characterizing the Microorganisms which are found

Organizational terminology

All organisms are classified by the science of alpha taxonomy into either taxa or clades. Taxonomy, sometimes alpha taxonomy, is the Science of finding describing and categorising Organisms thus giving rise to taxonomic groups or taxa A taxon (plural taxa) or taxonomic unit, is a name designating an organism or a group of Organisms In Biological nomenclature according to A clade is a taxonomic group comprising a single Common ancestor and all the descendants of that ancestor

Taxa are ranked groups of organisms which run from the general (domain) to the specific (species). In biological Taxonomy, a domain (also superregnum, superkingdom, or empire) is the highest Taxonomic rank of Organisms In Biology, a species is one of the basic units of Biological classification and a Taxonomic rank. A broad scheme of ranks in hierarchical order is:

• Domain
• Kingdom
• Phylum
• Class
• Order
• Family
• Genus
• Species

To give an example, Homo sapiens is the Latin binomial equating to modern humans. In biological Taxonomy, a domain (also superregnum, superkingdom, or empire) is the highest Taxonomic rank of Organisms In biological Taxonomy, a kingdom or regnum is a Taxonomic rank in either (historically the highest rank or (in the new three-domain system A phylum ( Plural: phyla) is a Taxonomic rank between Kingdom and above Class. A class is the Taxonomic rank in the Biological classification of organisms in Biology below phylum and above order. This article is about the taxonomic rank for the sequence of species in a taxonomic list see Taxonomic order In scientific classification used In Biological classification, family ( Latin A genus (plural genera from Γένος Latin genus "descent family type gender" is a low-level Taxonomic In Biology, a species is one of the basic units of Biological classification and a Taxonomic rank. Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus All members of the species sapiens are, at least in theory, genetically able to interbreed. Several species may belong to a genus, but the members of different species within a genus are unable to interbreed to produce fertile offspring. Homo, however, only has one surviving species (sapiens); Homo erectus, Homo neanderthalensis, &c. Homo is the Genus that includes modern humans and their close relatives Homo erectus ( Latin: "upright man" is an extinct species of the genus Homo, believed to have been the first hominin The Neanderthal (neɪˈændərtɑːl also with /niː-/ and /-θɔːl/ or Neandertal, is an extinct member of the Homo genus that is known from having become extinct thousands of years ago. Several genera belong to the same family and so on up the hierarchy. Eventually, the relevant kingdom (Animalia, in the case of humans) is placed into one of the three domains depending upon certain genetic and structural characteristics.

All living organisms known to science are given classification by this system such that the species within a particular family are more closely related and genetically similar than the species within a particular phylum.

A crab is an example of an organism. Crabs are decapod Crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (βραχύ / brachy

Chemistry

Organisms are complex chemical systems, organized in ways that promote reproduction and some measure of sustainability or survival. The molecular phenomena of chemistry are fundamental in understanding organisms, but it is a philosophical error (reductionism) to reduce organismal biology to mere chemistry. It is generally the phenomena of entire organisms that determine their fitness to an environment and therefore the survivability of their DNA based genes.

Organisms clearly owe their origin, metabolism, and many other internal functions to chemical phenomena, especially the chemistry of large organic molecules. Organisms are complex systems of chemical compounds which, through interaction with each other and the environment, play a wide variety of roles. A chemical compound is a substance consisting of two or more different elements chemically bonded together in a fixed proportion by Mass.

Organisms are semi-closed chemical systems. Although they are individual units of life (as the definition requires) they are not closed to the environment around them. To operate they constantly take in and release energy. Autotrophs produce usable energy (in the form of organic compounds) using light from the sun or inorganic compounds while heterotrophs take in organic compounds from the environment. An autotroph (from the Greek autos = self and trophe = nutrition is an Organism that produces complex Organic compounds from simple A heterotrophs, or chemoorganotrophy ( Greek heterone = (another and trophe = nutrition is an Organism that requires

The primary chemical element in these compounds is carbon. A chemical element is a type of Atom that is distinguished by its Atomic number; that is by the number of Protons in its nucleus. Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 The physical properties of this element such as its great affinity for bonding with other small atoms, including other carbon atoms, and its small size makes it capable of forming multiple bonds, make it ideal as the basis of organic life. It is able to form small compounds containing three atoms (such as carbon dioxide) as well as large chains of many thousands of atoms which are able to store data (nucleic acids), hold cells together and transmit information (protein). Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single A nucleic acid is a Macromolecule composed of chains of monomeric Nucleotides In Biochemistry these Molecules carry Genetic information Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl

Macromolecules

The compounds which make up organisms may be divided into macromolecules and other, smaller molecules. The term macromolecule by definition implies "large Molecule " The four groups of macromolecule are nucleic acids, proteins, carbohydrates and lipids. A nucleic acid is a Macromolecule composed of chains of monomeric Nucleotides In Biochemistry these Molecules carry Genetic information Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl Carbohydrates (from ' Hydrates of Carbon ' or saccharides ( Greek σάκχαρον meaning " Sugar " are the most Lipids are broadly defined as any fat- Soluble ( lipophilic) naturally-occurring Molecule, such as fats oils waxes cholesterol sterols fat-soluble Nucleic acids (specifically deoxyribonucleic acid, or DNA) store genetic data as a sequence of nucleotides. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known Nucleotides are Organic compounds that consist of three joined structures a nitrogenous base a Sugar, and a Phosphate group The particular sequence of the four different types of nucleotides (adenine, cytosine, guanine, and thymine) dictate the many characteristics which constitute the organism. Adenine is a Purine with a variety of roles in Biochemistry including Cellular respiration, in the form of both the energy-rich Adenosine Cytosine is one of the five main bases found in DNA and RNA. It is a Pyrimidine derivative with a Heterocyclic Aromatic ring Guanine is one of the five main Nucleobases found in the Nucleic acids DNA and RNA, the others being Adenine, Cytosine, Thymine is one of the four bases in the Nucleic acid of DNA that make up the letters ATGC The sequence is divided up into codons, each of which is a particular sequence of three nucleotides and corresponds to a particular amino acid. The genetic code is the set of rules by which information encoded in genetic material ( DNA or RNA sequences is translated into Proteins In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this Thus a sequence of DNA codes for a particular protein which, due to the chemical properties of the amino acids of which it is made, folds in a particular manner and so performs a particular function. Protein folding is the physical process by which a Polypeptide folds into its characteristic and functional three-dimensional structure.

The following functions of protein have been recognized:

1. Enzymes, which catalyze all of the reactions of metabolism;
2. Structural proteins, such as tubulin, or collagen;
3. Regulatory proteins, such as transcription factors or cyclins that regulate the cell cycle;
4. Signaling molecules or their receptors such as some hormones and their receptors;
5. Defensive proteins, which can include everything from antibodies of the immune system, to toxins (e. Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins A Tubulin is one of several members of a small family of globular Proteins The most common members of the tubulin family are α-tubulin and β-tubulin the proteins that Collagen is the main Protein of Connective tissue in Animals and the most abundant protein in Mammals making up about 50% of the whole-body protein In the field of Molecular biology, a transcription factor (sometimes called a sequence-specific DNA binding factor is a Protein that binds to specific sequences Hormones (from Greek ὁρμή - "impetus" are chemicals released by cells that affect cells in other parts of the body Antibodies (also known as immunoglobulins, abbreviated Ig) are Gamma globulin Proteins that are found in Blood or other Bodily An immune system is a collection of mechanisms within an Organism that protects against Disease by identifying and killing Pathogens and Tumor g. , dendrotoxins of snakes), to proteins that include unusual amino acids like canavanine. Dendrotoxins are a class of Neurotoxins produced by Mamba Snakes ( Dendroapsis) that block particular subtypes of Voltage-gated L-(+-( S)-Canavanine is a non- Proteinogenic Amino acid of certain leguminous plants.

Lipids make up the membrane of cells which constitutes a barrier, containing everything within the cell and preventing compounds from freely passing into, and out of, the cell. A lipid bilayer or bilayer lipid membrane ( BLM) is a membrane composed of Lipid molecules (usually Phospholipids. In some multi-cellular organisms they serve to store energy and mediate communication between cells. Carbohydrates also store and transport energy in some organisms, but are more easily broken down than lipids.

Structure

All organisms consist of monomeric units called cells; some contain a single cell (unicellular) and others contain many units (multicellular). The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called A microorganism (also spelled micro organism or micro-organism and also called a microbe) is an Organism that is Microscopic (usually Multicellular organisms are Organisms consisting of more than one cell, and having Differentiated cells that perform specialized functions Multicellular organisms are able to specialize cells to perform specific functions, a group of such cells is tissue the four basic types of which are epithelium, nervous tissue, muscle tissue and connective tissue. Tissue is a cellular organizational level intermediate between cells and a complete organism In biology and medicine epithelium is a tissue composed of cells that line the cavities and surfaces of structures throughout the body Nervous tissue is the fourth major class of Vertebrate tissue. Muscle (from Latin musculus, diminutive of mus "mouse" is contractile tissue of the body and is derived from the Connective tissue is one of the four types of tissue in traditional classifications (the others being epithelial, Muscle, and Nervous tissue) Several types of tissue work together in the form of an organ to produce a particular function (such as the pumping of the blood by the heart, or as a barrier to the environment as the skin). In Biology, an organ ( Latin: organum, "instrument tool" from Greek όργανον - organon "organ instrument The heart is a muscular organ in all Vertebrates responsible for pumping Blood through the Blood vessels by repeated rhythmic The skin is the outer covering of living tissue of an animal (or plant This pattern continues to a higher level with several organs functioning as an organ system to allow for reproduction, digestion, &c. In Biology, a system is a group of organs that work together to perform a certain task The reproductive system is a system of organs within an Organism which work together for the purpose of Reproduction. Digestion is the breaking down of chemicals in the body into a form that can be absorbed Many multicelled organisms comprise of several organ systems which coordinate to allow for life.

The cell

The cell theory, first developed in 1839 by Schleiden and Schwann, states that all organisms are composed of one or more cells; all cells come from preexisting cells; all vital functions of an organism occur within cells, and cells contain the hereditary information necessary for regulating cell functions and for transmitting information to the next generation of cells. Cell Theory refers to the idea that cells are the basic unit of structure in every living thing Matthias Jakob Schleiden ( April 5, 1804 - June 23, 1881) was a German Botanist and co-founder of the Cell theory Not to be confused with army general Theodore Schwan. ---- Theodor Schwann ( December 7, 1810 &ndash January Genetics (from Ancient Greek grc-Latn genetikos, “genitive” and that from grc-Latn genesis, “origin” a discipline of Biology, is

There are two types of cells, eukaryotic and prokaryotic. Prokaryotic cells are usually singletons, while eukaryotic cells are usually found in multi-cellular organisms. Prokaryotic cells lack a nuclear membrane so DNA is unbound within the cell, eukaryotic cells have nuclear membranes. The nuclear envelope (NE(also known as the perinuclear envelope, nuclear membrane, nucleolemma or karyotheca) is a double lipid bilayer that Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known

All cells, whether prokaryotic or eukaryotic, have a membrane, which envelopes the cell, separates its interior from its environment, regulates what moves in and out, and maintains the electric potential of the cell. The prokaryotes (proʊˈkærioʊts singular prokaryote /proʊˈkæriət/ are a group of Organisms that lack a Cell nucleus (= karyon or any other Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex The cell membrane (also called the plasma membrane, plasmalemma, or "phospholipid bilayer" is a Selectively permeable Lipid bilayer The Membrane potential, or better Membrane Voltage, is the difference of Electric potentials between two Aqueous solutions separated by a ( Inside the membrane, a salty cytoplasm takes up most of the cell volume. Salt is a Dietary mineral composed primarily of Sodium chloride that is essential for Animal life but toxic to most land plants The cytoplasm is the contents of a cell that is enclosed within the Plasma membrane. All cells possess DNA, the hereditary material of genes, and RNA, containing the information necessary to build various proteins such as enzymes, the cell's primary machinery. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units Gene expression is the process by which inheritable information from a Gene, such as the DNA sequence, is made into a functional Gene product, such Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins There are also other kinds of biomolecules in cells. A biomolecule is any organic Molecule that is produced by living Organisms including large Polymeric molecules such as Proteins

All cells share several abilities^[7]:

• Reproduction by cell division (binary fission, mitosis or meiosis). Cell division is a process by which a cell, called the parent cell divides into two or more cells called daughter cells. Binary fission is the form of Asexual reproduction and Cell division used by Prokaryotic organisms (such as Bacteria or Archea) Mitosis is the process in which a Eukaryotic cell separates the Chromosomes in its Cell nucleus, into two identical sets in two daughter nuclei In Biology or life science meiosis (pronounced my-oh-sis is a process of reductional division in which the number of chromosomes per cell is cut in half
• Use of enzymes and other proteins coded for by DNA genes and made via messenger RNA intermediates and ribosomes. Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl The genetic code is the set of rules by which information encoded in genetic material ( DNA or RNA sequences is translated into Proteins Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance Messenger ribonucleic acid ( mRNA) is a molecule of RNA encoding a chemical "blueprint" for a Protein product Ribosomes ( from ribo nucleic acid and "Greek soma ( meaning body") are complexes of RNA and Protein that
• Metabolism, including taking in raw materials, building cell components, converting energy, molecules and releasing by-products. Metabolism is the set of Chemical reactions that occur in living Organisms in order to maintain Life. In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by A by-product is a secondary or incidental product deriving from a Manufacturing process a Chemical reaction or a biochemical pathway and is not the primary product The functioning of a cell depends upon its ability to extract and use chemical energy stored in organic molecules. This energy is derived from metabolic pathways. In Biochemistry, a metabolic pathway is a series of chemical reactions occurring within a cell.
• Response to external and internal stimuli such as changes in temperature, pH or nutrient levels. In Biology, signal transduction refers to any process by which a cell converts one kind of signal or stimulus into another pH is the measure of the acidity or alkalinity of a Solution.
• Cell contents are contained within a cell surface membrane that contains proteins and a lipid bilayer. The cell membrane (also called the plasma membrane, plasmalemma, or "phospholipid bilayer" is a Selectively permeable Lipid bilayer A lipid bilayer or bilayer lipid membrane ( BLM) is a membrane composed of Lipid molecules (usually Phospholipids.

Life span

One of the basic parameters of organism is its life span. Some organisms live as short as one day, while some plants can live thousands of years. Aging is important when determining life span of most organisms, bacterium, a virus or even a prion. Senescence refers to the biological processes of a living Organism approaching an advanced age (i A prion (ˈpriːɒn is thought to be an infectious agent that according to current scientific consensus is comprised entirely of a propagated, mis-folded

Evolution

See also: Common descent and Origin of life

A hypothetical phylogenetic tree of all extant organisms, based on 16S rRNA gene sequence data, showing the evolutionary history of the three domains of life, bacteria, archaea and eukaryotes. A group of organisms is said to have common descent if they have a common Ancestor. In the Natural sciences, Abiogenesis, or origin of life, is the study of how Life on Earth emerged from Inanimate Organic A phylogenetic tree, also called an evolutionary tree, is a tree showing the Evolutionary relationships among various biological Species or other A non-coding RNA ( ncRNA) is any RNA molecule that is not translated into a Protein. History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance The three-domain system is a Biological classification introduced by Carl Woese in 1990 that divides cellular life forms into Archaea, The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex Originally proposed by Carl Woese. Carl Richard Woese (born July 15 1928, Syracuse New York) is an American Microbiologist who attended Deerfield Academy

In biology, the theory of universal common descent proposes that all organisms on Earth are descended from a common ancestor or ancestral gene pool. A group of organisms is said to have common descent if they have a common Ancestor.

Evidence for common descent may be found in traits shared between all living organisms. In Darwin's day, the evidence of shared traits was based solely on visible observation of morphologic similarities, such as the fact that all birds have wings, even those which do not fly. Today, there is strong evidence from genetics that all organisms have a common ancestor. For example, every living cell makes use of nucleic acids as its genetic material, and uses the same twenty amino acids as the building blocks for proteins. A nucleic acid is a Macromolecule composed of chains of monomeric Nucleotides In Biochemistry these Molecules carry Genetic information In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl The universality of these traits strongly suggests either common ancestry or intelligent design.

The "Last Universal Ancestor" is the name given to the hypothetical single cellular organism or single cell that gave rise to all life on Earth 3. A microorganism (also spelled micro organism or micro-organism and also called a microbe) is an Organism that is Microscopic (usually 9 to 4. 1 billion years ago; however, this hypothesis has since been refuted on many grounds. For example, it was once thought that the genetic code was universal (see: universal genetic code), but differences in the genetic code and differences in how each organism translates nucleic acid sequences into proteins, provide support that there never was any "last universal common ancestor. The genetic code is the set of rules by which information encoded in genetic material ( DNA or RNA sequences is translated into Proteins The genetic code is the set of rules by which information encoded in genetic material ( DNA or RNA sequences is translated into Proteins " Back in the early 1970s, evolutionary biologists thought that a given piece of DNA specified the same protein subunit in every living thing, and that the genetic code was thus universal. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known In Structural biology, a protein subunit or subunit protein is a single Protein Molecule that assembles (or " coassembles " Since this is something unlikely to happen by chance, it was interpreted as evidence that every organism had inherited its genetic code from a single common ancestor, aka. , the "Last Universal Ancestor. " In 1979, however, exceptions to the code were found in mitochondria, the tiny energy factories inside cells. Biologists subsequently found exceptions in bacteria and in the nuclei of algae and single-celled animals. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have In Cell biology, the nucleus (pl nuclei; from Latin la ''nucleus'' or la ''nuculeus'' "little nut" or kernel is a membrane-enclosed Algae ( sing. alga are a large and diverse group of simple typically Autotrophic organisms ranging from Unicellular to Multicellular forms It is now clear that the genetic code is not the same in all living things, and that it does not provide powerful evidence that all living things evolved on a single tree of life. ^[8] Further support that there is no "Last Universal Ancestor" has been provided over the years by Lateral gene transfer in both prokaryote and eukaryote single cell organisms. The prokaryotes (proʊˈkærioʊts singular prokaryote /proʊˈkæriət/ are a group of Organisms that lack a Cell nucleus (= karyon or any other Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex This is why phylogenetic trees cannot be rooted, why almost all phylogenetic trees have different branching structures, particularly near the base of the tree, and why many organisms have been found with codons and sections of their DNA sequence that are unrelated to any other species. A phylogenetic tree, also called an evolutionary tree, is a tree showing the Evolutionary relationships among various biological Species or other The genetic code is the set of rules by which information encoded in genetic material ( DNA or RNA sequences is translated into Proteins A DNA sequence or genetic sequence is a succession of letters representing the Primary structure of a real or hypothetical DNA Molecule

Information about the early development of life includes input from the fields of geology and planetary science. Planetary science, also known as planetology and closely related to planetary astronomy, is the Science of Planets or Planetary systems These sciences provide information about the history of the Earth and the changes produced by life. However, a great deal of information about the early Earth has been destroyed by geological processes over the course of time.

History of life

Main article: Timeline of evolution

The chemical evolution from self-catalytic chemical reactions to life (see Origin of life) is not a part of biological evolution, but it is unclear at which point such increasingly complex sets of reactions became what we would consider, today, to be living organisms. This timeline of the evolution of life outlines the major events in the development Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst Life is a state that distinguishes Organisms from non-living objects such as non-life and dead organisms being manifested by growth through Metabolism In the Natural sciences, Abiogenesis, or origin of life, is the study of how Life on Earth emerged from Inanimate Organic

Precambrian stromatolites in the Siyeh Formation, Glacier National Park. The Precambrian ( Pre-Cambrian) is an informal name for the supereon comprising the eons of the Geologic timescale that came before the current Stromatolites (from Greek στρώμα strōma, mattress bed stratum and λιθος lithos, rock are layered accretionary Structures formed in Glacier National Park is located in the US state of Montana, bordering the Canadian provinces of Alberta and British Columbia. In 2002, William Schopf of UCLA published a controversial paper in the journal Nature arguing that formations such as this possess 3. The University of California Los Angeles (generally known as UCLA) is a public research university located in Westwood Los Angeles, California, United Nature is a prominent Scientific journal, first published on 4 November 1869 5 billion year old fossilized algae microbes. FOSSIL is a standard protocol for allowing serial communication for Telecommunications programs under the DOS Operating system. Algae ( sing. alga are a large and diverse group of simple typically Autotrophic organisms ranging from Unicellular to Multicellular forms If true, they would be the earliest known life on earth.

Not much is known about the earliest developments in life. However, all existing organisms share certain traits, including cellular structure and genetic code. The genetic code is the set of rules by which information encoded in genetic material ( DNA or RNA sequences is translated into Proteins Most scientists interpret this to mean all existing organisms share a common ancestor, which had already developed the most fundamental cellular processes, but there is no scientific consensus on the relationship of the three domains of life (Archaea, Bacteria, Eukaryota) or the origin of life. Scientific consensus is the collective judgement position and Opinion of the community of Scientists in a particular field of Science at a particular The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex In the Natural sciences, Abiogenesis, or origin of life, is the study of how Life on Earth emerged from Inanimate Organic Attempts to shed light on the earliest history of life generally focus on the behavior of macromolecules, particularly RNA, and the behavior of complex systems. The term macromolecule by definition implies "large Molecule " Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units This article describes complex system as a type of system For other meanings see Complex systems.

The emergence of oxygenic photosynthesis (around 3 billion years ago) and the subsequent emergence of an oxygen-rich, non-reducing atmosphere can be traced through the formation of banded iron deposits, and later red beds of iron oxides. Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy. Banded iron formations (also known as banded ironstone formations or BIF s are a distinctive type of rock often found in primordial ( Precambrian) Sedimentary The term red beds usually refers to strata of reddish -colored sedimentary rocks such as Sandstone, Siltstone or Shale that This was a necessary prerequisite for the development of aerobic cellular respiration, believed to have emerged around 2 billion years ago. Cellular respiration is the set of the metabolic reactions and processes that take place in Organisms cells to convert biochemical energy from Cellular respiration is the set of the metabolic reactions and processes that take place in Organisms cells to convert biochemical energy from

In the last billion years, simple multicellular plants and animals began to appear in the oceans. Soon after the emergence of the first animals, the Cambrian explosion (a period of unrivaled and remarkable, but brief, organismal diversity documented in the fossils found at the Burgess Shale) saw the creation of all the major body plans, or phyla, of modern animals. The Cambrian explosion or Cambrian radiation was the seemingly rapid appearance of most major groups of complex Animals around, as evidenced by the See also Burgess shale type fauna The Burgess Shale is famous for the exceptional preservation of the fossils found within it in which the soft parts are preserved A phylum ( Plural: phyla) is a Taxonomic rank between Kingdom and above Class. This event is now believed to have been triggered by the development of the Hox genes. A homeobox is a DNA sequence found within Genes that are involved in the regulation of patterns of development ( Morphogenesis) in Animals About 500 million years ago, plants and fungi colonized the land, and were soon followed by arthropods and other animals, leading to the development of land ecosystems with which we are familiar. Plants are living Organisms belonging to the kingdom Plantae. A fungus (ˈfʌŋgəs is a eukaryotic Organism that is a member of the kingdom Fungi (ˈfʌndʒaɪ Arthropods are Animals belonging to the Phylum Arthropoda (from Greek ἄρθρον arthron, " Joint " An ecosystem is a natural unit consisting of all plants animals and micro-organisms( Biotic factors in an area functioning together with all of the non-living physical (

The evolutionary process may be exceedingly slow. Fossil evidence indicates that the diversity and complexity of modern life has developed over much of the history of the earth. The history of Earth covers approximately 46 billion years (4567000000 years from Earth ’s formation out of the Solar nebula to the present Geological evidence indicates that the Earth is approximately 4.6 billion years old. Geology (from Greek γη gê, "earth" and λόγος Logos, "speech" lit Modern geologists and Geophysicists consider the age of Earth to be around 4 Studies on guppies by David Reznick at the University of California, Riverside, however, have shown that the rate of evolution through natural selection can proceed 10 thousand to 10 million times faster than what is indicated in the fossil record. ^[9]. Such comparative studies however are invariably biased by disparities in the time scales over which evolutionary change is measured in the laboratory, field experiments, and the fossil record.

Horizontal gene transfer, and the history of life

The ancestry of living organisms has traditionally been reconstructed from morphology, but is increasingly supplemented with phylogenetics - the reconstruction of phylogenies by the comparison of genetic (DNA) sequence.

"Sequence comparisons suggest recent horizontal transfer of many genes among diverse species including across the boundaries of phylogenetic 'domains'. History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance In Biology, a species is one of the basic units of Biological classification and a Taxonomic rank. Thus determining the phylogenetic history of a species can not be done conclusively by determining evolutionary trees for single genes. " ^[10]

Biologist Gogarten suggests "the original metaphor of a tree no longer fits the data from recent genome research", therefore "biologists [should] use the metaphor of a mosaic to describe the different histories combined in individual genomes and use [the] metaphor of a net to visualize the rich exchange and cooperative effects of HGT among microbes. " ^[11]

References

External links

• BBCNews: 27 September, 2000, When slime is not so thick Citat: ". . . It means that some of the lowliest creatures in the plant and animal kingdoms, such as slime and amoeba, may not be as primitive as once thought. . . . "
  • SpaceRef.com, July 29, 1997: Scientists Discover Methane Ice Worms On Gulf Of Mexico Sea Floor
    • The Eberly College of Science: Methane Ice Worms discovered on Gulf of Mexico Sea Floor download Publication quality photos
  • Artikel, 2000: Methane Ice Worms: Hesiocaeca methanicola. Colonizing Fossil Fuel Reserves
  • SpaceRef.com, May 04, 2001: Redefining "Life as We Know it" Hesiocaeca methanicola In 1997, Charles Fisher, professor of biology at Penn State, discovered this remarkable creature living on mounds of methane ice under half a mile of ocean on the floor of the Gulf of Mexico.
• BBCNews, 18 December, 2002, 'Space bugs' grown in lab Citat: ". . . Bacillus simplex and Staphylococcus pasteuri. . . Engyodontium album. . . The strains cultured by Dr Wainwright seemed to be resistant to the effects of UV - one quality required for survival in space. . . . "
• BBCNews, 19 June, 2003, Ancient organism challenges cell evolution Citat: ". . . "It appears that this organelle has been conserved in evolution from prokaryotes to eukaryotes, since it is present in both,". . . "
• Interactive Syllabus for General Biology - BI 04, Saint Anselm College, Summer 2003
• Jacob Feldman: Stramenopila
• NCBI Taxonomy entry: root (rich)
• Saint Anselm College: Survey of representatives of the major Kingdoms Citat: ". . . Number of kingdoms has not been resolved. In biological Taxonomy, a kingdom or regnum is a Taxonomic rank in either (historically the highest rank or (in the new three-domain system . . Bacteria present a problem with their diversity. . . Protista present a problem with their diversity. Protists (ˈproʊtɨst are a diverse group of eukaryotic Microorganisms Historically protists were treated as the kingdom Protista but this . . ",
• Species 2000 Indexing the world's known species. Species 2000 has the objective of enumerating all known species of plants, animals, fungi and microbes on Earth as the baseline dataset for studies of global biodiversity. It will also provide a simple access point enabling users to link from here to other data systems for all groups of organisms, using direct species-links.
• The largest organism in the world may be a fungus carpeting nearly 10 square kilometers of an Oregon forest, and may be as old as 10500 years.
• The Tree of Life.
• Frequent questions from kids about life and their answers