A phenotypic characteristic, acquired during growth and development, that is not genetically based and therefore cannot be passed on to the next generation for example, the large muscles of a weightlifter. Any heritable characteristic of an organism that improves its ability to survive and reproduce in its environment. Also used to describe the process of genetic change within a population, as influenced by natural selection. A graph of the average fitness of a population in relation to the frequencies of genotypes in it.
See Article History Chemical compound, any substance composed of identical molecules consisting of atoms of two or more chemical elements.
All the matter in the universe is composed of the atoms of more than different chemical elementswhich are found both in pure form and combined in chemical compounds.
A sample of any given pure element is composed only of the atoms characteristic of that element, and the atoms of each element are unique.
For example, the atoms that constitute carbon are different from those that make up ironwhich are in turn different from those of gold. Every element is designated by a unique symbol consisting of one, two, or three letters arising from either the current element name or its original often Latin name.
For example, the symbols for carbon, hydrogenand oxygen are simply C, H, and O, respectively. The symbol for iron is Fe, from its original Latin name ferrum.
The fundamental principle of the science of chemistry is that the atoms of different elements can combine with one another to form chemical compounds. Methanefor example, which is formed from the elements carbon and hydrogen in the ratio four hydrogen atoms for each carbon atom, is known to contain distinct CH4 molecules.
The formula of a compound—such as CH4—indicates the types of atoms present, with subscripts representing the relative numbers of atoms although the numeral 1 is never written. A water molecule is made up of two hydrogen atoms and one oxygen atom. A single oxygen atom contains six electrons in its outer shell, which can hold a total of eight electrons.
When two hydrogen atoms are bound to an oxygen atom, the outer electron shell of oxygen is filled. Waterwhich is a chemical compound of hydrogen and oxygen in the ratio two hydrogen atoms for every oxygen atom, contains H2O molecules. Sodium chloride is a chemical compound formed from sodium Na and chlorine Cl in a 1: Although the formula for sodium chloride is NaCl, the compound does not contain actual NaCl molecules.
See below Trends in the chemical properties of the elements for a discussion of the process for changing uncharged atoms to ions [i. The substances mentioned above exemplify the two basic types of chemical compounds: Methane and water are composed of molecules; that is, they are molecular compounds.
Sodium chloride, on the other hand, contains ions; it is an ionic compound. Ions—atoms with a positive or negative net charge—bind together to form ionic compounds. Molecular compounds are formed when molecules, such as those of methane or water, join together by sharing electrons.
The atoms of the various chemical elements can be likened to the letters of the alphabet: In fact, there are millions of chemical compounds known, and many more millions are possible but have not yet been discovered or synthesized. Most substances found in nature—such as wood, soil, and rocks—are mixtures of chemical compounds.
These substances can be separated into their constituent compounds by physical methods, which are methods that do not change the way in which atoms are aggregated within the compounds.
Compounds can be broken down into their constituent elements by chemical changes. A chemical change that is, a chemical reaction is one in which the organization of the atoms is altered. An example of a chemical reaction is the burning of methane in the presence of molecular oxygen O2 to form carbon dioxide CO2 and water.
Chemical compounds show a bewildering array of characteristics. At ordinary temperatures and pressures, some are solidssome are liquidsand some are gases. The colours of the various compounds span those of the rainbow. Some compounds are highly toxic to humans, whereas others are essential for life.
Substitution of only a single atom within a compound may be responsible for changing the colour, odour, or toxicity of a substance. So that some sense can be made out of this great diversityclassification systems have been developed.
An example cited above classifies compounds as molecular or ionic.
Compounds are also classified as organic or inorganic. Organic compounds see below Organic compoundsso called because many of them were originally isolated from living organisms, typically contain chains or rings of carbon atoms. Because of the great variety of ways that carbon can bond with itself and other elements, there are more than nine million organic compounds.
The compounds that are not considered to be organic are called inorganic compounds see below Inorganic compounds. Hg is the only metal element that is liquid at room temperature.AAE. Cellmark’s dedicated team provides forensic anthropology and archaeology expertise, supported by access to an extensive range of environmental evidence analysis.
Junk DNA is a popular term for DNA that does not contain genes. This is non-coding DNA. Most of the genome consists of non-coding DNA. Because it does not . Now, Salk Institute scientists have created a new tool that targets not DNA, but RNA, and used it to correct a protein imbalance in cells from a dementia patient, restoring them to healthy levels.
DNA replication State that DNA replication occurs in a 5? → 3? direction. DNA replication occurs in a 5'→3' direction. Explain the process of DNA replication in prokaryotes, including the role of enzymes (helicase, DNA polymerase, RNA primase and DNA ligase), Okazaki fragments and deoxynucleoside triphosphates.
Activities. Make an Origami DNA model at DNAi website. Or download the PDF files for Instructions and Template.; Take the "Tour of the Basics" at the Genetic Science Learning benjaminpohle.com this Activity, simulate "RNA Transcription" and get the Templates for RNA and DNA benjaminpohle.com are suggestions for the order of DNA bases.
They can be cut out and one given to each group. Long Life Spans: "Adam Lived Years and Then He Died" New Discoveries in the Biochemistry of Aging Support the Biblical Record By Fazale R.