Evabetoms revision cards ((science)the best)

the process by which different kinds of living organism are believed to have developed from earlier forms during the history of the earth.the gradual depment of something.

"The fossil record is incomplete! Where are the missing links?" ask creationists. Yes, the fossil record is "incomplete". The only way it could be "complete" would be if literally every single living thing had been fossilised after it died. That doesn't happen, because the process of fossilisation is incredibly unlikely, especially for land creatures.

People sometimes complain that evolution is "unfalsifiable". What they mean by that is that a scientific idea should make testable predictions, and that evolution, apparently, doesn't – so, if the theory of evolution is false, you can't prove it false.

That's nonsense. There are dozens – thousands – of testable predictions that the theory of evolution implies. Let's take a look at one subset: The geographical spread of species.

Evolution has to work on what already exists. If it's true, then we would expect to see that, for instance, body parts in one species can be mapped onto those of another, because they share an ancestor.

And that's exactly what we do find. Look at the human hand. It has five fingers, each with four bones, including the one in the body of the hand. And if you look at the forearms of all mammals, you'll see the same structure.

The most striking evidence that all creatures share the same ancestor is this: They all share the same basic genetic code. The gene for an eye in a fruit fly will make an eye in a mouse. DNA is the language that all life talks in (unless you count viruses as alive, and even they use RNA, a simpler molecule, to hijack the DNA in other creatures' cells).

The geographical spread of species is limited by their ancestry, as we've seen. But sometimes species separated by thousands of miles face similar challenges. A herbivore on the grass plains of North America would have the same sort of problems that a herbivore on the savannahs of sub-Saharan Africa would. If evolution were true, you would expect unrelated species to have evolved to come up with similar solutions.

And lo and behold, that's true. The American pronghorn looks and behaves much like an African antelope, but is not an antelope and is only very distantly related to them. Because it faced fast-moving predators on wide grass plains, it evolved long legs for sprinting and a nervous disposition, like its equivalents in Africa.

Normally we think of evolution as something that happens over thousands or millions of years, and it often is. But there are plenty of examples of it happening in human timescales.

The most famous example is the peppered moth, which lives in forests in Britain and is camouflaged against tree bark. Up until the 19th century they were all white, but when the Industrial Revolution blackened the trees in British forests, the white colouring became much more visible. In 1811 a first dark specimen was recorded, a mutant. Against the dark trees they were much harder for predators to spot. By the end of the century it outnumbered the white ones. But as the heavily polluting industries in Britain fell away in the 20th century, and the forests became cleaner again, the white moth became more common.

A scientific theory is a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment. Such fact-supported theories are not "guesses" but reliable accounts of the real world. The theory of biological evolution is more than "just a theory." It is as factual an explanation of the universe as the atomic theory of matter or the germ theory of disease. Our understanding of gravity is still a work in progress. But the phenomenon of gravity, like evolution, is an accepted fact.