evolution

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evolution

 [ev″o-lu´shun]
the process of development in which an organ or organism becomes more and more complex by the differentiation of its parts; a continuous and progressive change according to certain laws and by means of resident forces.
convergent evolution the development, in animals that are only distantly related, of similar structures or functions in adaptation to similar environments.

ev·o·lu·tion

(ev'ō-lū'shŭn),
1. A continuing process of change from one state, condition, or form to another.
2. A progressive distancing between the genotype and the phenotype in a line of descent.
3. The liberation of a gas or heat in the course of a chemical or enzymatic reaction.
[L. e-volvo, pp. -volutus, to roll out]

evolution

(ĕv′ə-lo͞o′shən, ē′və-)
n.
1. A continuing process of change from one state, condition, or form to another.
2. Change in the genetic composition of a population during successive generations, often resulting in the development of new species. The mechanisms of evolution include natural selection acting on the genetic variation among individuals, mutation, migration, and genetic drift.

ev·o·lu·tion

(ev'ŏ-lū'shŭn)
1. A continuing process of change from one state, condition, or form to another.
2. A progressive distancing between the genotype and the phenotype in a line of descent.
[L. e-volvo, pp. -volutus, to roll out]

evolution

The theory that all living organisms have developed in complexity, from a simple life form. Evolution occurs by the natural selection of those who, by the fortune of spontaneous random changes (mutations), happen to be best suited to their contemporary environment, to survive and reproduce. It does not occur by the passing on to offspring of characteristics acquired during the lifetime of an individual. Characteristics are passed on by the transmission of DNA from parents to offspring and, unless mutation has occurred, this DNA is an identical copy of the DNA of preceding generations.

evolution

an explanation of the way in which present-day organisms have been produced, involving changes taking place in the genetic make-up of populations that have been passed on to successive generations. According to DARWINISM, evolutionary MUTATIONS have given rise to changes that have, through NATURAL SELECTION, either survived in better adapted organisms (see ADAPTATION, GENETIC), or died out. Evolution is now generally accepted as the means which gives rise to new species (as opposed to SPECIAL CREATION) but there is still debate about exactly how it has taken place and how rapidly changes can take place. See LAMARCKISM.

Patient discussion about evolution

Q. How the bacterias are produced?

A. The Bacteria are a large group of unicellular microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals. (The name comes from the Greek bakterion, meaning small staff.) Bacteria are ubiquitous in every habitat on Earth, growing in soil, acidic hot springs, radioactive waste,[2] water, and deep in the Earth's crust, as well as in organic matter and the live bodies of plants and animals. There are typically 40 million bacterial cells in a gram of soil and a million bacterial cells in a millilitre of fresh water; in all, there are approximately five nonillion (5×1030) bacteria on Earth,[3] forming much of the world's biomass.[4] Bacteria are vital in recycling nutrients, with many important steps in nutrient cycles depending on these organisms, such as the fixation of nitrogen from the atmosphere and putrefaction. http://en.wikipedia.org/wiki/Bacteria Hope this helps.

More discussions about evolution
References in periodicals archive ?
One of Darwin's aims in Origin was to demonstrate how the traditional taxonomic challenges of biological classification can be resolved if we view the natural world as the "strictly genealogical" result of descent with modification. In a bid to clarify his proposal for overhauling the time-honored systems of morphological classification, Darwin called upon yet another linguistic analogy.
Since ancestors are rarely available for direct examination, we must accept that homology is usually a hypothesis about evolutionary history rather than a deduced matter of fact." (34) All these results clearly reveal the ambiguity and uncertainty associated with the origin of species as descent with modification from a common ancestor.
But the historical development of the Corvette, which Berra calls "descent with modification," is undeniably due to construction according to preexisting plans--that is, design.
Assuming descent with modification, characteristics are more likely to evolve only once and become passed on to descendants than the alternative, which would require traits to evolve more than once in independent lineages.
Gayon contends that we observe this "expansion" of a theoretical framework in the generalization of the concept of "descent with modification" to infra-organismic levels, and the addition of new principles in the source of variation--lateral gene transfer and symbiosis (p.
Natural Selection, Diversity of Organisms, and Speciation are emphasized at a higher frequency than Evidence for Evolution, Pace and Rate of Evolution, Descent with Modification, and Human Evolution (Table 1).
Most people think of evolution as the mechanism by which new species arise from common ancestors (descent with modification), but this is emphatically not what Wade is talking about.