Natural selection revision 1. Complete the gaps in the paragraph using the words in the box below: Natural selection can also be called ‘____________ of the ___________’. The ‘fittest’ organisms are the ones that are most well _____________ for the environment that they are in. The organisms that survive will be able to ________________ and pass on the ____________ that gave them the advantage to their _______________. Over time, the characteristics of a particular species will change to allow ____________ in their environment. This is called _________________. evolution fittest adapted offspring genes reproduce survival survival 2. Why are the bacteria in Stage 1 different colours? Stage 1 _______________________________________ _______________________________________ _______________________________________ Stage 2 3. Why is there a reduction in bacteria between Stage 1 and Stage 2? _______________________________________ _______________________________________ Stage 3 _______________________________________ 4. Explain what happens between Stage 2 and Stage 3. ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ 5. Why is genetic variation so important to a population of organisms? ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ PRACTISE EXAM-STYLE QUESTIONS Natural Selection Q1. The image below shows Phiomia (an ancestor of elephants) and a modern African elephant. Phiomia lived about 35 million years ago. Both Phiomia an the African elephant reach up into trees to get leaves. a) Use Darwin’s theory of natural selection to explain how the elephant’s trunk evolved (4) ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… b) Describe the causes of variation in a population. (2) ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… Q2. a) Some rats have a mutation, which enables them to eat rat poison and survive. Suggest how the use of Warfarin as a poison could lead to an increase in the number of rats with this mutation. (2) ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… b) Some farmers regularly give their cows low doses of antibiotics. This can increase the amount of milk that the cows make. Suggest why the regular use of low doses of antibiotics may make this problem worse. (2) ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… MARK SCHEME Natural selection Q1 a) b) Q2 a) b)
