![]() ![]() That’s fact one: a fancy word for this over-reproduction is ‘super fecundity’. He saw that organisms produce more offspring than is required to replace themselves, so population sizes should increase rapidly (think about the number of frogspawn laid each year, or how many eggs a spider lays). The first inference is drawn from three facts which Darwin observed in the natural world around him. Eventually, as more evidence accumulated and these different ideas were tested it became clear that Darwin was right all along!įigure: modified from One Long Argument by Ernst Mayr (1991) Before then scientists would favour some ideas but propose alternatives to fill in the gaps, natural selection was one of the least popular, to find out why click here. Scientists however took a while to see this they weren’t accepted as a package until the modern synthesis of the 1930/40s. Natural selection: evolutionary change occurs through variation between individuals some variants give the individual an extra survival probability.ĭarwin considered all these theories as parts of one grand idea they all occur together.Gradualism: evolutionary change occurs through incremental small changes within populations new species are not created suddenly.Species multiply: the diversification of life involves populations of one species diverging until they become two separate species this has probably occurred billions of times on earth!.Common descent: organisms are descended from one, or several common ancestors and have diversified from this original stock.Evolution: species come and go through time, while they exist they change. ![]() Historians and biologists who have analysed Darwin’s work, for example Ernst Mayr, have identified fivetheories which Darwin outlined in On the Origin of Species, and which work together to bring about evolution. For natural selection to work, it has to occur along with a bunch of other things. ![]()
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