Biology carbon dating
Carbon-12 and carbon-14 are two isotopes of the element carbon.The difference between carbon-12 and carbon-14 is the number of neutrons in each atom.Atoms of carbon-12 have 6 neutrons, while atoms of carbon-14 contain 8 neutrons.neutral atom would have the same number of protons and electrons, so a neutral atom of carbon-12 or carbon-14 would have 6 electrons. sexual reproduction Reproduction that involves the fusion of gametes. It fused with another, smaller paleocontinent, Kazakhstania, in the Carboniferous. Abnormal erythrocytes containing iron granules in the mitochondria. OVERVIEW OF SIGNAL TRANSDUCTION PATHWAYS Silurian Period (S) /sə-LURE-ee-ən/ n. In humans the sex chromosomes comprise the 23rd chromosome pair. In certain crosses sex-linked traits manifest themselves only in the heterogametic sex. The paleocontinent Siberia came into existence as a separate entity in the Cambrian. Most signal transduction processes are ordered sequences of intracellular reactions ("signal transduction pathways") mediated by enzymes and activated by second messengers. MORE INFORMATION Sitophilus /sigh-TAWF-ə-ləs, sə-/ n. An economically important genus of weevils, which are highly destructive of grains. The study of nutrition and dietetics — sitologist /sigh-TAWL-ə-jist, -jəst/ sitosterol (also β-sitosterol) /SIDE-ō-STAIR-awl/ n. Chemical element; atomic number 11, atomic weight 22.98976928. The sticky tip of a carpel; the stigmata are the parts of a flower that receive pollen. Microscopic pores in the epidermis of plants; stomata allow gas exchange with the atmosphere. A baglike, elastic portion of the digestive tract following the esophagus. It secretes acidic gastric juices that convert proteins into peptones. stratum corneum /STRAT-əm KORN-ee-əm/ (pl strata cornea /STRAT-ə KORN-ee-ə/) The outermost, horny layer of the skin. superoxide dismutase (SOD) /SOO-pər-AWK-sīd DIS-myoo-tāz/ n. An enzyme that catalyzes the conversion of superoxide into hydrogen peroxide and oxygen. suture (1) a line of union forming an immovable joint (as in the skull or between the segments of a gastropod shell) SUTURES OF HUMAN SKULL | SUTURES IN A DEER SKULL (2) surgical stitches uniting two parts (or the line of union so formed).
In genomic mapping, a series of contigs, in the correct order but not necessarily assembled into a single continuous sequence. A white, soluble compound used as an antacid and found in carbonated drinks and baking powders. The cells of the body taken as a whole, in opposition to germ cells. MORE INFORMATION | CHART OF RELATIVE TAXONOMIC RANKS spectral karyotype (SKY) /KARE-ee-ō-type/ n. A genus of gram-positive cocci usually present on human skin and mucous membranes. strepticemia /strep-tə-SEEM-ee-yə/ (also streptococcemia /STREP-tə-cock-SEEM-ee-yə/) Presence of streptococci in the blood. However, some are both common and among the most dangerous of human pathogens. Some stromatolites are among the most ancient fossils known, dating to about 3.5 billion years ago. subkingdom (also infrakingdom, superdivision, superphylum) n. In taxonomy, a division of a kingdom; specifically, a category ranking beneath an kingdom, but above a phylum. Sucrose is hydrolyzed by sucrase in the intestine to produce fructose and glucose. A functional group of the form —C—SH or —R—SH, where R is an alkane, alkene, or some other group of atoms containing carbon. Synthetic substances containing the sulfonamide group, many of which are used as antimicrobial agents.
(1) a substance produced and emitted by a gland; (2) the action wherein a gland produces and emits a substance or substances; secretion can be of two types, external and internal. Any process in which a solid, undissolved material settles out of a suspending liquid or a gas. Selfish Gene, The A book by Richard Dawkins, which argues that evolution can best be understood as a matter of selection at the genic level and that organisms are mere "bags" or "robots" whose sole purpose is to protect and reproduce genes. Union of male and female gametes from the same individual. Pollinating a stigma with pollen from the same plant. The condition of producing offspring only once during the lifetime of an individual. Semen is produced by males and injected into the female during copulation, an necessary prerequisite of fertilization. Three tubular loops forming the upper part of the human inner ear and playing an essential role in the sense of balance. sequence tagged site (STS) A short (200-500 base-pair) DNA fragment, with a known location and sequence, that occurs only once in a genome. During the Silurian, the earliest known vascular plants appeared on land. Sinanthropus pekinensis A name formerly assigned to remains of early hominids found near Beijing (then Peking), which are now assigned to Homo erectus.
The normal biological process whereby the chromatids of each chromosome pair are separated during meiosis and randomly distributed to the germ cells. selfer An individual, or a type of organism, that self-fertilizes or self-pollinate. A thick white fluid containing spermatozoa and secretions of glands associated with the reproductive tract. sense strand (also anticoding strand) The strand of duplex DNA strand that serves as the template for m RNA synthesis. Presence of pathogenic microorganisms or their toxic products in the bloodstream. A wall separating two cells, cavities or bodily regions (e.g., the nasal septum). sequence assembly A process whereby the order of multiple sequenced DNA fragments is determined. This composite continent later joined with Baltica to form Pangea in the Permian. A chemical group, often with a chainlike structure, attached to a main chain or ring. A geologic period of the Paleozoic Era lasting from 443.7 ± 1.5 to 416.0 ± 2.8 mya.
(1) a hard, external, shieldlike plate; in vertebrates scuta may be composed of horn or bone; in invertebrates they are generally chitinous; (2) the largest of the four parts covering the upper surface of the thorax of an insect. second messenger A molecule that relays a message — carried by a hormone from elsewhere in the body to the surface of a cell — to some point within the cell. Any solid material that settles out of a suspending liquid or a gas. sedimentary rock /sed-ə-MENT-er-ee, British: sed-ə-MEN-tree/ n. Expressed sequence tags (ESTs) are STSs derived from c DNAs. CODONS | MOLECULAR STRUCTURE | SERINE BIOSYNTHESIS serous fluid /SIR-əs/ n. Specifically: the three membranes lining the pleural, pericardial, and peritoneal cavities. single nucleotide polymorphism (SNP) /pawl-ee-MORE-fiz-əm/ n. DNA sequence variations that occur when a single nucleotide (A, T, C, or G) in the genome sequence is altered. When this occurs, each forms a duplicate of itself and the resulting two structures, called sister chromatids, are joined at the centromere. An instrument used to accurately administer small amounts of fluid; when a needle is attached to a syringe it can be used to make injections. systematist One who engages in the practice of systematics. On the Origins of New Forms of Life Mammalian Hybrids Cat-rabbit Hybrids: Fact or fiction?
In external secretion the substance is not emitted into the blood, whereas in internal secretion it is — secretory /SEEK-rə-tore-ee, see-KREE-tə-ree/ sediment /SED-ə-mənt/ n. sedimentation coefficient (S) /sed-ə-men-TAY-shən co-ə-FISH-ənt/ n. A value indicating the rate at which a particular type of molecule moves through a solution during centrifugation as it settles toward its equilibrium position in the centrifugation gradient. An encapsulated plant embryo in an arrested state of development and, usually, surrounded by endosperm. This is the opposite view from that taken in the theoretical portion of this website, which argues that evolution is typically a matter of selection among distinct, stable types of organisms. STSs are useful for correlating mapping and sequence data reported from different laboratories since they are unique and detectable by polymerase chain reaction. READ ABOUT THE DIET OF SNAKES sessile /SESS-əl/ adj. The first coral reefs formed in the oceans, and fish with movable jaws made their appearance and eurypterids were abundant. single-gene disorder Hereditary disorder caused by a mutant allele of a single gene (e.g., Duchenne muscular dystrophy, retinoblastoma, sickle cell disease). A block of genes occurring in the same order in two different types of organisms. During the eukaryotic cell cycle, a substage of interphase when each of the chromosomes replicate. systematics (also taxonomy) The study of the classification of living things.
The region between the Sahara desert and savannas to the south; characterized by extended dry seasons, which alternate with relatively brief rainy seasons. The salt concentration of a solution, particularly of a body of water. Saprophites are often called "decomposers." sarcoma /sar-KŌM-ə/ n. Specific types of sarcomas are named for the types of tissue from which they arise (e.g., angiosarcoma, chondrosarcoma, hemangiosarcoma, leiomyosarcoma, liposarcoma, lymphangiosarcoma, osteosarcoma, rhabdomyosarcoma). The sarcomere is the fundamental unit of muscle structure. PICTURES Scholastics (also schoolmen) Christian medieval philosophers. During spermiogenesis, each haploid spermatid develops, without further division, into a functionally mature spermatozoon. Either of two types of cells that originate from the spermatogonium during spermatogenesis and that develop, via division into spermatids. spermatogonium (pl spermatogonia) /sperm-awd-ə-GŌ-nee-əm, pl -nee-ə/ n. subclass (also infraclass, superorder) In taxonomy, a division of a class; specifically, a category ranking beneath a class, but above an order.