ARTIFICIAL AND NATURAL SELECTION ESSAY SELECTION IN AN ECOSYSTEM CAN OCCUR NATURALLY AND/OR ARTIFICIALLY Write an essay in which you use a named example of a domesticated animal and a named example of a crop species to describe how the process of artificial selection occurs in each named example and the advantages of the process to each sample. Discuss TWO ways how artificial selection differs from natural selection in one of the named examples This is an inordinately verbose question in that the first sentence seems to be never ending. This sentence could easily be split into three – breaking things down makes life easier for us. This is how I would have done or how you should do it in the exam if a question like this comes up again: 1 Write an essay in which you use a named example of a domesticated animal and a named example of a crop species. 2 Describe how the process of artificial selection occurs in each named examples. 3 State the advantages of the process to each sample. 4 Discuss TWO ways how artificial selection differs from natural selection in one of the named examples • Okay, so now you can find the main headings from the information given • If you are using Understanding Life Science, then you have the examples given on page 101 (second edition, second impression. In the older version, see page 325). Isaac uses cows and hens (by selecting cows to produce large amounts of milk. Plus, watermelons – by deliberate selection of POLYPLOID plants bigger watermelons have been produced. In Focus, look at page 252/254 (milk and maize examples). • Then make clear points to gain the full 17 marks • The other 3 marks will be given by the examiner only if the essay is logical and focused • It will be marked on artificial selection, two advantages and two differences between artificial and natural selection. Domesticated Animal Species - Dog In dog evolution from wolf ancestors the main focus of selection was for tameness i.e. being comfortable around humans and establishing a close bond with them A cross between the fox and the dog has led to a variety of dogs. - Advantages: an increase in genetic variation within the dog gene pool. tameness of animal (1 example + max. 4 + 2 advantages = 7) Domesticated Crop Species - Maize wild grasses were artificially interbred with Zea mays (maize) produce larger cobs• in nature these species do not interbreed• Advantages: maize cobs show an increase in the size a number of rows of kernels (1 example + max. 3 + 2 advantages = 6) Differences between artificial and natural selection 1 In natural selection the selection force is the environment while in artificial selection it is a human need 2 In natural selection the best adapted organisms survive• while in artificial selection it is not the best adapted that are necessarily allowed to survive• since humans artificially nurture and reproduce them. Any 2x2 (4)
Posted on: Thu, 14 Nov 2013 16:17:20 +0000
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