Geological formations consisting of underground enclosures with access from the surface.

Inland bodies of standing FRESHWATER usually smaller than LAKES. They can be man-made or natural but there is no universal agreement as to their exact size. Some consider a pond to be a small body of water that is shallow enough for sunlight to reach the bottom.

A phylum of photosynthetic EUKARYOTA bearing double membrane-bound plastids containing chlorophyll a and b. They comprise the classical green algae, and represent over 7000 species that live in a variety of primarily aquatic habitats. Only about ten percent are marine species, most live in freshwater.

Techniques used to determine the age of materials, based on the content and half-lives of the RADIOACTIVE ISOTOPES they contain.

Water containing no significant amounts of salts, such as water from RIVERS and LAKES.

Cultivation of natural faunal resources of water. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)

The scientific study of past societies through artifacts, fossils, etc.

Proteins found in any species of algae.

The family of carnivorous or omnivorous bears, having massive bodies, coarse heavy fur, relatively short limbs, and almost rudimentary tails.

The relationships of groups of organisms as reflected by their genetic makeup.

A species of GREEN ALGAE. Delicate, hairlike appendages arise from the flagellar surface in these organisms.

The period of history before 500 of the common era.

Remains, impressions, or traces of animals or plants of past geological times which have been preserved in the earth's crust.

'Paintings' are not a medical term, but rather an artistic expression involving the application and manipulation of pigments on a surface to create an image or design, which has no direct medical relevance or definition.

An order of fish with 26 families and over 3,000 species. This order includes the families CYPRINIDAE (minnows and CARPS), Cobitidae (loaches), and Catostomidae (suckers).

Common name for an extinct species of the Homo genus. Fossils have been found in Europe and Asia. Genetic evidence suggests that limited interbreeding with modern HUMANS (Homo sapiens) took place.

The presence of bacteria, viruses, and fungi in water. This term is not restricted to pathogenic organisms.

Deoxyribonucleic acid that makes up the genetic material of algae.

Nonmotile unicellular green algae potentially valuable as a source of high-grade protein and B-complex vitamins.

A functional system which includes the organisms of a natural community together with their environment. (McGraw Hill Dictionary of Scientific and Technical Terms, 4th ed)

An order of mostly marine CRUSTACEA containing more than 5500 species in over 100 families. Like ISOPODA, the other large order in the superorder Peracarida, members are shrimp-like in appearance, have sessile compound eyes, and no carapace. But unlike Isopoda, they possess thoracic gills and their bodies are laterally compressed.

A family of fresh water fish in the order CHARACIFORMES, which includes the Tetras.

A genus of GREEN ALGAE in the family Ulvaceae. Commonly know as sea lettuces, they grow attached to rocks and KELP in marine and estuarine waters.

Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.

A phylum of oxygenic photosynthetic bacteria comprised of unicellular to multicellular bacteria possessing CHLOROPHYLL a and carrying out oxygenic PHOTOSYNTHESIS. Cyanobacteria are the only known organisms capable of fixing both CARBON DIOXIDE (in the presence of light) and NITROGEN. Cell morphology can include nitrogen-fixing heterocysts and/or resting cells called akinetes. Formerly called blue-green algae, cyanobacteria were traditionally treated as ALGAE.

The inanimate matter of Earth, the structures and properties of this matter, and the processes that affect it.

A group of cold-blooded, aquatic vertebrates having gills, fins, a cartilaginous or bony endoskeleton, and elongated bodies covered with scales.

A multistage process that includes cloning, physical mapping, subcloning, determination of the DNA SEQUENCE, and information analysis.

A non-taxonomic term for unicellular microscopic algae which are found in both freshwater and marine environments. Some authors consider DIATOMS; CYANOBACTERIA; HAPTOPHYTA; and DINOFLAGELLATES as part of microalgae, even though they are not algae.

A mass of organic or inorganic solid fragmented material, or the solid fragment itself, that comes from the weathering of rock and is carried by, suspended in, or dropped by air, water, or ice. It refers also to a mass that is accumulated by any other natural agent and that forms in layers on the earth's surface, such as sand, gravel, silt, mud, fill, or loess. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed, p1689)

Multicellular marine macroalgae including some members of red (RHODOPHYTA), green (CHLOROPHYTA), and brown (PHAEOPHYTA) algae. They are widely distributed in the ocean, occurring from the tide level to considerable depths, free-floating (planktonic) or anchored to the substratum (benthic). They lack a specialized vascular system but take up fluids, nutrients, and gases directly from the water. They contain CHLOROPHYLL and are photosynthetic, but some also contain other light-absorbing pigments. Many are of economic importance as FOOD, fertilizer, AGAR, potash, or source of IODINE.

"Engraving, in the context of medicine, refers to the process of cutting or carving designs, letters, or images into a hard surface, such as a metal plate or a gemstone, to create a printing plate for producing multiple identical impressions or reproductions."

Constituent of 30S subunit prokaryotic ribosomes containing 1600 nucleotides and 21 proteins. 16S rRNA is involved in initiation of polypeptide synthesis.

The study of early forms of life through fossil remains.

DNA sequences encoding RIBOSOMAL RNA and the segments of DNA separating the individual ribosomal RNA genes, referred to as RIBOSOMAL SPACER DNA.

The process of cumulative change over successive generations through which organisms acquire their distinguishing morphological and physiological characteristics.

A genus of GREEN ALGAE in the family Volvocaceae. They form spherical colonies of hundreds or thousands of bi-flagellated cells in a semi-transparent gelatinous ball.

The synthesis by organisms of organic chemical compounds, especially carbohydrates, from carbon dioxide using energy obtained from light rather than from the oxidation of chemical compounds. Photosynthesis comprises two separate processes: the light reactions and the dark reactions. In higher plants; GREEN ALGAE; and CYANOBACTERIA; NADPH and ATP formed by the light reactions drive the dark reactions which result in the fixation of carbon dioxide. (from Oxford Dictionary of Biochemistry and Molecular Biology, 2001)

Marine, freshwater, or terrestrial mollusks of the class Gastropoda. Most have an enclosing spiral shell, and several genera harbor parasites pathogenic to man.

A family of CRUSTACEA, order DECAPODA, comprising the penaeid shrimp. Species of the genus Penaeus are the most important commercial shrimp throughout the world.

A common name (but used formally) for a group of organisms that are mostly kinds of algae including BACILLARIOPHYTA; OOMYCETES; PHAEOPHYCEAE; and CHRYSOPHYCEAE. They all contain CHLOROPLASTS that are thought to have been derived from the endosymbiosis of ancient RED ALGAE.

The science of the earth and other celestial bodies and their history as recorded in the rocks. It includes the study of geologic processes of an area such as rock formations, weathering and erosion, and sedimentation. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)