Natural selectionIB MYP Biology: Flashcards

Exam questions on Natural selection

1. In the nineteenth century two naturalists, Charles Darwin and Alfred Russel Wallace, worked separately in different parts of the world. Darwin collected animals and plants in South America and on the Galápagos Islands. Wallace collected specimens in the Amazon rainforest and the islands of South-East Asia. Both noticed that members of the same species differ from one another, and that parents produce many more offspring than can possibly survive. In 1858 their ideas were presented together to a scientific society in London.
   Explain why the production of more offspring than can survive leads to competition.2 marks
2. Before the 1840s, almost all the peppered moths in the English city of Manchester were pale with dark speckles. Dark moths were extremely rare. As factories burned coal, soot blackened the tree trunks where the moths rested during the day, and birds hunted the moths by sight. By 1895 about 98% of the peppered moths in the city were dark. After clean-air laws reduced soot in the 1960s, the trunks became paler again, and the pale form became common once more.
   Explain why the pale form became common again after the clean-air laws.2 marks
3. A class models predation using paper dots. They scatter 50 red and 50 green paper dots of identical size on a large area of short green grass. Each student acts as a bird and has 30 seconds to pick up as many dots as possible, one at a time. The dots left behind are 'survivors'. Over the whole class, 36 red dots and 18 green dots were picked up in the first round.
   State a testable hypothesis for this investigation, give a scientific reason for it, and identify the independent variable.3 marks