The Manchester Mark 1 computer developed by Frederic Calland Williams — and Tom Kilburn — ; historically significant because of its pioneering inclusion of index registers. EDSAC — the first complete, fully functional computer inspired by the von Neumann architecturethe basis of every modern computer — constructed by Maurice Wilkes — The integrated circuitcommonly called the microchip, conceptualised and built by Geoffrey Dummer —
The concept was later extended to include any biological system from the cell to the entire biosphereall the areas of Earth inhabited by living things. Unity All living organisms, regardless of their uniqueness, have certain biological, chemical, and physical characteristics in common.
All, for example, are composed of basic units known as cells and of the same chemical substances, which, when analyzed, exhibit noteworthy similarities, even in such disparate organisms as bacteria and humans. Furthermore, since the action of any organism is determined by the manner in which its cells interact and since all cells interact in much the same way, the basic functioning of all organisms is also similar.
Animal cells and plant cells contain membrane-bound organelles, including a distinct nucleus. In contrast, bacterial cells do not contain organelles. There is not only unity of basic living substance and functioning but also unity of origin of all living things.
If, however, life originated on Earth more than once in the past, the fact that all organisms have a sameness of basic structure, compositionand function would seem to indicate that only one original type succeeded.
A common origin of life would explain why in humans or bacteria—and in all forms of life in between—the same chemical substance, deoxyribonucleic acid DNAin the form of genes accounts for the ability of all living matter to replicate itself exactly and to transmit genetic information from parent to offspring.
Furthermore, the mechanisms for that transmittal follow a pattern that is the same in all organisms. Whenever a change in a gene a mutation occurs, there is a change of some kind in the organism that contains the gene.
It is this universal phenomenon that gives rise to the differences variations in populations of organisms from which nature selects for survival those that are best able to cope with changing conditions in the environment. Evolution itself is a biological phenomenon common to all living things, even though it has led to their differences.
Evidence to support the theory of evolution has come primarily from the fossil recordfrom comparative studies of structure and function, from studies of embryological development, and from studies of DNA and RNA ribonucleic acid.
Three types of natural selection, showing the effects of each on the distribution of phenotypes within a population. The downward arrows point to those phenotypes against which selection acts.
Stabilizing selection left column acts against phenotypes at both extremes of the distribution, favouring the multiplication of intermediate phenotypes.
Directional selection centre column acts against only one extreme of phenotypes, causing a shift in distribution toward the other extreme.
Diversifying selection right column acts against intermediate phenotypes, creating a split in distribution toward each extreme. Diversity Despite the basic biological, chemical, and physical similarities found in all living things, a diversity of life exists not only among and between species but also within every natural population.
The phenomenon of diversity has had a long history of study because so many of the variations that exist in nature are visible to the eye. The fact that organisms changed during prehistoric times and that new variations are constantly evolving can be verified by paleontological records as well as by breeding experiments in the laboratory.
Long after Darwin assumed that variations existed, biologists discovered that they are caused by a change in the genetic material DNA.
That change can be a slight alteration in the sequence of the constituents of DNA nucleotidesa larger change such as a structural alteration of a chromosomeor a complete change in the number of chromosomes.
In any case, a change in the genetic material in the reproductive cells manifests itself as some kind of structural or chemical change in the offspring. The consequence of such a mutation depends upon the interaction of the mutant offspring with its environment.
It has been suggested that sexual reproduction became the dominant type of reproduction among organisms because of its inherent advantage of variability, which is the mechanism that enables a species to adjust to changing conditions.
New variations are potentially present in genetic differences, but how preponderant a variation becomes in a gene pool depends upon the number of offspring the mutants or variants produce differential reproduction.
Thus, when a species is introduced into a new habitatit either adapts to the change by natural selection or by some other evolutionary mechanism or eventually dies off.
Because each new habitat means new adaptationshabitat changes have been responsible for the millions of different kinds of species and for the heterogeneity within each species.Ian Wilmut and his colleagues attempted fusions between donor cells and unfertilized eggs.
Only 29 of those fused cells became embryos and were introduced into (13) ewes. Of those 29, only one became pregnant and gave birth to Dolly.
English inventions and discoveries are objects, processes or techniques invented, innovated or discovered, partially or entirely, in England by a person from England (that is, someone born in England – including to non-English parents – or born abroad with at least one English parent and who had the majority of their education or career in England).
Principles of Cloning, Second Edition is the fully revised edition of the authoritative book on the science of cloning.
The book presents the basic biological mechanisms of how cloning works and progresses to discuss current and potential applications in basic biology, agriculture, biotechnology, and medicine.
Ian Wilmut and the Cloning of Dolly Definitions of creativity vary based on different people’s interpretations, yet most people agree that creative individuals produce new ideas that can completely change or invent a domain. This is a list of people who have made notable contributions to genetics.
The growth and development of genetics represents the work of many people. Dolly, the world’s most famous and controversial sheep, was born twenty years ago – on July 5, to be initiativeblog.com was the first mammal .