BETH YW DAMCANIAETH? WHAT IS A THEORY? Nid yw gwyddonwyr yn gwybod sut mae pob dim yn gweithio. Scientists don’t understand how everything works. Mae rhai gwyddonwyr yn ceisio dyfalu sut mae proses cymhleth yn gweithio. Some scientists try and guess how complicated processes work. Mae’r syniad yma yn cael ei alw yn DAMCANIAETH. The new idea is called a THEORY

Yn 19eg ganrif cynyddodd gwybodaeth gwyddonol. Cychwynnodd rhai gwyddonwyr ofyn cwestiynau am sut daeth dyn i’r Ddaear yn y lle cyntaf. ‘Roedd rhan fwyaf o bobl y cyfnod yn credu y Beibl, mai Duw creodd dyn ar y Ddaear. Daeth gwyddonydd a damcaniaeth newydd am sut gwnaeth organebau byw ddatblygu ar y Ddaear dros cyfnod hir o amser. Charles Darwin ( 1808 – 1882) Scientific knowledge increased in the 19 th century Some scientists began to ask questions about how man first came to be on the Earth. Most people of the age believed in the Bible, that God created man and the Earth. A scientist came up with two theories to explain how living organisms developed over a very long period of time on Earth.

Charles Darwin Bu dadlau mawr am ddamcaniaeth Darwin am esblygiad bywyd ar y blaned, oherwydd yr hyn oedd pobl yn ei gredu fel gair Duw yn y Beibl am darddaid bywyd ar y Ddaear. There was much controversy about Darwin’s theory of Evolution of life on the planet, because of people’s belief in God’s word in the Bible which explained how life began on the Earth.

DAMCANIAETH DARWIN AM ESBLYGIAD DARWIN’S THEORY OF EVOLUTION Organebau syml iawn oedd ar y Ddaear i gychwyn. Dros amser, newidodd ffurf yr organebau i rhai mwy cymhleth. Marwodd rhai organebau allan yn llwyr gan eu bod methu addasu i newidiadau yn yr amgylchedd. DIFODIAD. Rheini oedd yn medru goroesi, y mwyaf ffit, pasiodd eu genynnau ymlaen i’w hepil. Proses araf, hir yw esblygiad. The first organisms on Earth were very simple. Over time the form of organisms changed and became more complex. Some organisms died out because they could not adapt to the changing environment. Those that could survive, the fittest, passed on their genes on to their offspring. Evolution is a slow, long process.

Y TYSTIOLAETH THE EVIDENCE FFOSILIAU FOSSILS Yn ystod oes Darwin dargafuwyd nifer fawr o ffosilau o anifeiliad oedd ddim yn byw ar wyneb y Ddaear, yr oeddent wedi DIFODI. During Darwin’s life, many fossils of long disappeared animals were discovered, they had become EXTINCT.

GWAITH YMCHWIL DARWIN DARWIN’S RESEARCH WORK Fe gasglodd Darwin dystiolaeth am ei ddamcaniaeth o bob rhan o’r byd. Fe aeth ar fordaith am 5 mlynnedd gan ymweld ag ynysoedd y Galapagos, de America ac Awstralia. Dadansoddodd ei dystiolaeth yn wyddonol ac yn greadigol. Daeth i gasgliadau ar sael y dystiolaeth Dyma yw sael y broses wyddonol hyd yn oed heddiw. Darwin collected evidence for his theory from all over the world. He went on a sea voyage for 5 years when he visited the Galapagos islands, South America and Australia. He analysed his evidence scientifically and creatively. He came to conclusions based on his evidence This is the basis of scientific research even today.

ESBLYGIAD YN DIGWYDD HEDDIW EVOLUTION HAPPENING TODAY Warfarin is an anti-coagulant (stops blood clotting) drug, used both in the treatment of thrombosis in humans and as a poison for rats and mice. Obviously the amounts administered to humans are carefully controlled, whereas the aim in giving it to rats is to kill them. Warfarin works by interfering with the normal blood-clotting mechanism. In humans this is useful because thromboses are basically blood clots, and in controlled doses warfarin can be used therapeutically. In rats, the idea is to so interfere with the normal blood clotting that the normal rapid repair of small blood vessel leakages does not occur. The rat then dies from internal bleeding. Warfarin was first used in Britain in It was extremely effective at killing rodents, so it was used extensively. Resistance to warfarin was first noticed in Welshpool in 1959.

Mae gwyddonwyr yn gweld hyn yn dystiolaeth bod esblygiad yn digwydd mewn anifeiliaid heddiw. Mewn poblogaeth o lygod rhaid bod un o leiaf gyda ymwrthedd naturiol i effaith Warfarin. Mae hyn oherwydd genyn gwahanol yn DNA y lygoden. Mi wnaeth y lygoden oroesi ddigon hir i atgenhedlu a pasio mlaen ei enynnau manteisiol i’r epil, sydd hefyd yn ei dro yn datblygu ymwrthedd i’r gwenwyn. Scientists see this as evidence of evolution happening in animals today. In a population of rats, at least one may have had resistance to the effects of Warfarin. This is because of a different gene in the DNA of the rat. The rat lived long enough to breed and pass on its beneficial gene to it’s offspring, which also developed resistance to the poison.