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| Biology for OCR A - Heinemann |
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Biology for OCR A. Bryan Dawson and Ian Honeysett. Heinemann. 2001 This textbook is not accurate in its description of the theory of evolution, or the evidence for it. The weaknesses of the theory are not acknowledged, and no alternatives are mentioned.Evidence for EvolutionThe text states clearly that most mutations are harmful, giving the examples of cystic fibrosis and Down’s syndrome. With no proven examples, it goes on to claim that when random changes lead to improvement they have a massive impact on the evolution of the species (p.124) and goes on to speculate that the evolution of feathers on birds’ wings possibly started with a useful mutation. The reader is not informed that beneficial mutations are essential to the theory of evolution, and the lack of proven examples is a problem for the theory. This textbook under-emphasises the role of mutation in the theory of evolution and gives the misleading impression that recombination is the process which provides the variation for evolution to occur. It describes recombination in a section How does sex lead to variation? then refers to sexual reproduction as the source of variation in evolution: Over millions of years of evolution, life on Earth has developed from single-celled organisms into the wonderfully varied and complex life forms that we see around us today. For this variety to have occurred, genetic information had to be passed on from parent to offspring through the genes by the process of sexual reproduction. The variation that this produces allows evolution to occur, selecting those individuals that are best suited to survive in a changing environment. (p. 116). Evolution occurs as a result of the variation produced by sexual reproduction. (p. 134). Recombination due to sexual reproduction cannot on its own provide the new variations needed by the theory of evolution, because it is simply the reshuffling of existing information. The Peppered Moth is used as an example of evolution by natural selection. However, the authors mistakenly present this as a case of the gradual evolution of a dark moth: …the darker moths survived to reproduce and some of their offspring were even darker…it was not long before the peppered moth had become almost black... (p. 134) This is factually inaccurate. There are two forms of the peppered moth, one form is light and speckled and the other is black. They appear to differ with respect to the alleles of a single gene. The black form did not evolve through the light form gradually becoming darker. The authors also fail to mention that the experimental evidence for this story is now widely acknowledged to be flawed. The process of allopatric speciation is described, with no examples or evidence given. The section on evidence for evolution begins: Because we cannot travel back in time, we cannot prove that evolution actually happened. However, the circumstantial evidence for it is overwhelming (p. 135) The only example of this overwhelming evidence is The Fossil Record. We can look at fossils and build up a picture of what happened to the organisms over a long period of time. We can see how they changed to be best suited to their environment (p. 135). No more detail is given, which is likely to leave the reader with the false impression that the fossil record gives abundant evidence for gradual evolution. Pupils taking single-award Biology cover a chapter on Diversity and Adaptation. Here the central role of mutation is explained more clearly: ...mutations produce variation, and natural selection allows those that are best suited to each environment to survive. (p. 154). This chapter has an account of mammalian limbs, which, unusually for a textbook, emphasises their differences rather than their similarities, though there is no suggestion that differences are just as much evidence against evolution as similarities are evidence for evolution. Sometimes the result of evolution is that organisms look very different even though they might be closely related. This is the case with some of the mammals. Their limbs have evolved to help them survive in different habitats. Although they carry out different jobs, the limbs are built to the same pattern. (p. 154). There is a section on the Development of Antibiotic Resistance in bacteria (p. 186), which is entirely accurate. Teaching the controversy? This textbook makes no suggestion that Darwinism is a controversial theory of origins. It dogmatically asserts that evolution has occured. The huge number of different organisms on the earth has been produced by the process of evolution. (p. 154). |
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A fair result can be obtained only by fully stating and balancing the facts and arguments on both sides of each question. Charles Darwin |
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