Organism

The bacterium Escherichia coli (E. coli), is a single-celled prokaryote
An amoeba is a single-celled eukaryote
Polypore fungi and angiosperm trees are large multicellular eukaryotes.
Precambrian stromatolites in the Siyeh Formation, Glacier National Park. In 2002, a paper in the scientific journal Nature suggested that these 3.5 Gya (billion years old) geological formations contain fossilized cyanobacteria microbes. This suggests they are evidence of one of the earliest known life forms on Earth.
LUCA may have used the Wood–Ljungdahl or reductive acetyl–CoA pathway to fix carbon.

Organism is any organic, living system that functions as an individual entity.

- Organism
The bacterium Escherichia coli (E. coli), is a single-celled prokaryote

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Alpha

(A) Electron micrograph of Halothiobacillus neapolitanus cells, arrows highlight carboxysomes. (B) Image of intact carboxysomes isolated from H. neapolitanus. Scale bars are 100 nm.

Organelle

Organelle is a specialized subunit, usually within a cell, that has a specific function.

Organelle is a specialized subunit, usually within a cell, that has a specific function.

(A) Electron micrograph of Halothiobacillus neapolitanus cells, arrows highlight carboxysomes. (B) Image of intact carboxysomes isolated from H. neapolitanus. Scale bars are 100 nm.
Structure of Candidatus Brocadia anammoxidans, showing an anammoxosome and intracytoplasmic membrane

In biology organs are defined as confined functional units within an organism.

Production of new individuals along a leaf margin of the miracle leaf plant (Kalanchoe pinnata). The small plant in front is about 1 cm (0.4 in) tall. The concept of "individual" is obviously stretched by this asexual reproductive process.

Reproduction

Production of new individuals along a leaf margin of the miracle leaf plant (Kalanchoe pinnata). The small plant in front is about 1 cm (0.4 in) tall. The concept of "individual" is obviously stretched by this asexual reproductive process.
Hoverflies mating in midair flight
Illustration of the twofold cost of sexual reproduction. If each organism were to contribute to the same number of offspring (two), (a) the population remains the same size each generation, where the (b) asexual population doubles in size each generation.

Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents.

Lactose is a disaccharide found in animal milk. It consists of a molecule of D-galactose and a molecule of D-glucose bonded by beta-1-4 glycosidic linkage.

Carbohydrate

Biomolecule consisting of carbon , hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula Cm(H2O)n (where m may or may not be different from n).

Biomolecule consisting of carbon , hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula Cm(H2O)n (where m may or may not be different from n).

Lactose is a disaccharide found in animal milk. It consists of a molecule of D-galactose and a molecule of D-glucose bonded by beta-1-4 glycosidic linkage.
D-glucose is an aldohexose with the formula (C·H2O)6. The red atoms highlight the aldehyde group and the blue atoms highlight the asymmetric center furthest from the aldehyde; because this -OH is on the right of the Fischer projection, this is a D sugar.
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Glucose can exist in both a straight-chain and ring form.
Sucrose, also known as table sugar, is a common disaccharide. It is composed of two monosaccharides: D-glucose (left) and D-fructose (right).
Grain products: rich sources of carbohydrates
Glucose tablets

Carbohydrate metabolism is the series of biochemical processes responsible for the formation, breakdown and interconversion of carbohydrates in living organisms.

Cell division in prokaryotes (binary fission) and eukaryotes (mitosis and meiosis)

Cell division

Process by which a parent cell divides, when a mother cell divides into two or more daughter cells.

Process by which a parent cell divides, when a mother cell divides into two or more daughter cells.

Cell division in prokaryotes (binary fission) and eukaryotes (mitosis and meiosis)
Divisome and elongasome complexes responsible for peptidoglycan synthesis during lateral cell-wall growth and division.
Image of the mitotic spindle in a human cell showing microtubules in green, chromosomes (DNA) in blue, and kinetochores in red
Cell division over 42. The cells were directly imaged in the cell culture vessel, using non-invasive quantitative phase contrast time-lapse microscopy.
Kurt Michel with his phase-contrast microscope

For simple unicellular microorganisms such as the amoeba, one cell division is equivalent to reproduction – an entire new organism is created.

The three-domains tree and the Eocyte hypothesis (Two domains tree), 2008.

Domain (biology)

The three-domains tree and the Eocyte hypothesis (Two domains tree), 2008.
Phylogenetic tree showing the relationship between the eukaryotes and other forms of life, 2006 Eukaryotes are colored red, archaea green, and bacteria blue.

In biological taxonomy, a domain ( or ) (Latin: regio ), also dominion, superkingdom, realm, or empire, is the highest taxonomic rank of all organisms taken together.

This fluid lipid bilayer cross section is made up entirely of phosphatidylcholine.

Lipid bilayer

Thin polar membrane made of two layers of lipid molecules.

Thin polar membrane made of two layers of lipid molecules.

This fluid lipid bilayer cross section is made up entirely of phosphatidylcholine.
The three main structures phospholipids form in solution; the liposome (a closed bilayer), the micelle and the bilayer.
Schematic cross sectional profile of a typical lipid bilayer. There are three distinct regions: the fully hydrated headgroups, the fully dehydrated alkane core and a short intermediate region with partial hydration. Although the head groups are neutral, they have significant dipole moments that influence the molecular arrangement.
TEM image of a bacterium. The furry appearance on the outside is due to a coat of long-chain sugars attached to the cell membrane. This coating helps trap water to prevent the bacterium from becoming dehydrated.
Diagram showing the effect of unsaturated lipids on a bilayer. The lipids with an unsaturated tail (blue) disrupt the packing of those with only saturated tails (black). The resulting bilayer has more free space and is, as a consequence, more permeable to water and other small molecules.
Illustration of a GPCR signaling protein. In response to a molecule such as a hormone binding to the exterior domain (blue) the GPCR changes shape and catalyzes a chemical reaction on the interior domain (red). The gray feature is the surrounding bilayer.
Transmission Electron Microscope (TEM) image of a lipid vesicle. The two dark bands around the edge are the two leaflets of the bilayer. Historically, similar images confirmed that the cell membrane is a bilayer
Human red blood cells viewed through a fluorescence microscope. The cell membrane has been stained with a fluorescent dye. Scale bar is 20μm.
3d-Adapted AFM images showing formation of transmembrane pores (holes) in supported lipid bilayer
Illustration of a typical AFM scan of a supported lipid bilayer. The pits are defects in the bilayer, exposing the smooth surface of the substrate underneath.
Structure of a potassium ion channel. The alpha helices penetrate the bilayer (boundaries indicated by red and blue lines), opening a hole through which potassium ions can flow
Schematic illustration of pinocytosis, a type of endocytosis
Exocytosis of outer membrane vesicles (MV) liberated from inflated periplasmic pockets (p) on surface of human Salmonella 3,10:r:- pathogens docking on plasma membrane of macrophage cells (M) in chicken ileum, for host-pathogen signaling in vivo.
Schematic showing two possible conformations of the lipids at the edge of a pore. In the top image the lipids have not rearranged, so the pore wall is hydrophobic. In the bottom image some of the lipid heads have bent over, so the pore wall is hydrophilic.
Illustration of lipid vesicles fusing showing two possible outcomes: hemifusion and full fusion. In hemifusion, only the outer bilayer leaflets mix. In full fusion both leaflets as well as the internal contents mix.
Schematic illustration of the process of fusion through stalk formation.
Diagram of the action of SNARE proteins docking a vesicle for exocytosis. Complementary versions of the protein on the vesicle and the target membrane bind and wrap around each other, drawing the two bilayers close together in the process.

The cell membranes of almost all organisms and many viruses are made of a lipid bilayer, as are the nuclear membrane surrounding the cell nucleus, and membranes of the membrane-bound organelles in the cell.

Modern stromatolites in Shark Bay, Western Australia. It can take a century for a stromatolite to grow 5 cm.

Unicellular organism

Modern stromatolites in Shark Bay, Western Australia. It can take a century for a stromatolite to grow 5 cm.
A bottom-dwelling community found deep in the European Arctic.
Paramecium tetraurelia, a ciliate, with oral groove visible
A scanning electron microscope image of a diatom
Transmission electron microscope image of budding Ogataea polymorpha

A unicellular organism, also known as a single-celled organism, is an organism that consists of a single cell, unlike a multicellular organism that consists of multiple cells.

A representation of the 3D structure of myoglobin, showing alpha helices, represented by ribbons. This protein was the first to have its structure solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a Nobel Prize in Chemistry

Biomolecule

A representation of the 3D structure of myoglobin, showing alpha helices, represented by ribbons. This protein was the first to have its structure solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a Nobel Prize in Chemistry
Stereo 3D image of a group I intron ribozyme (PDB file 1Y0Q); gray lines show base pairs; ribbon arrows show double-helix regions, blue to red from 5' to 3' end; white ribbon is an RNA product.

A biomolecule or biological molecule is a loosely used term for molecules present in organisms that are essential to one or more typically biological processes, such as cell division, morphogenesis, or development.

In the first stage of sexual reproduction, "meiosis", the number of chromosomes is reduced from a diploid number (2n) to a haploid number (n). During "fertilisation", haploid gametes come together to form a diploid zygote, and the original number of chromosomes is restored.

Sexual reproduction

Type of reproduction that involves a complex life cycle in which a gamete with a single set of chromosomes (haploid) combines with another to produce a zygote that develops into an organism composed of cells with two sets of chromosomes (diploid).

Type of reproduction that involves a complex life cycle in which a gamete with a single set of chromosomes (haploid) combines with another to produce a zygote that develops into an organism composed of cells with two sets of chromosomes (diploid).

In the first stage of sexual reproduction, "meiosis", the number of chromosomes is reduced from a diploid number (2n) to a haploid number (n). During "fertilisation", haploid gametes come together to form a diploid zygote, and the original number of chromosomes is restored.
An Australian emperor dragonfly laying eggs, guarded by a male
Flowers contain the sexual organs of flowering plants.
Puffballs emitting spores

This can lead organisms to extreme efforts in order to reproduce, such as combat and display, or produce extreme features caused by a positive feedback known as a Fisherian runaway.

Algae

False-color scanning electron micrograph of the unicellular coccolithophore Gephyrocapsa oceanica
title page of Gmelin's Historia Fucorum, dated 1768
The kelp forest exhibit at the Monterey Bay Aquarium: A three-dimensional, multicellular thallus
Rock lichens in Ireland
Floridian coral reef
Algae on coastal rocks at Shihtiping in Taiwan
Phytoplankton, Lake Chūzenji
Harvesting algae
Seaweed-fertilized gardens on Inisheer
Dulse, a type of edible seaweed
Algae bladder

Algae (singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms.