B3 Life on Earth

1. B3 Life on Earth Lesson 7: The Great Competition of Life

2. Objectives • MUST explain the process of natural selection • SHOULD distinguish between natural selection and selective breeding • COULD explain how variation between individuals may eventually lead to change in species and interpret data on changes in species caused by natural selection

3. Key Words • You need to be able to define the following: • Natural selection • Selective breeding

6. Textbook Answers 1) Because of environmental and genetic variation. 2) From parent to child in the sex cells (eggs and sperm). 3) The process by which features desired by humans are exaggerated in a species through a breeding programme; individuals with features most similar to those desired are bred together to give offspring that have the desired feature more strongly than the previous generation; this is repeated over many generations. 4) Both need genetic variation on which to act, but only natural selection favours genes that help the organism survive in the wild; selective breeding tends to take place more quickly than natural selection; human intervention is needed in selective breeding but it is not needed in natural selection.

7. Textbook Answers 5) The organism might have more offspring; these offspring might also have the genes for the advantageous trait, and so might have more offspring of their own; in this way, the gene that gives those that carry it the advantage would become more frequent in the population. 6) The pattern shown is that as the smoke pollution decreased, the percentage of melanic (dark) coloured moths also decreased; these became less-well camouflaged as surfaces became less sooty, and so were preyed on more than the pale variety; the peppered moth is now mostly found in its pale form probably because there is much less smoke pollution in the UK, as factories and power stations have become cleaner because of higher standards for air quality.

8. Worksheet Answers Activity 1 (Low demand) Students can choose any of the features. • A Likely to be the first to a kill or able to outrun other lions if running away with meat; being better fed means survival to reproduction more likely. • B Lions often hunt in packs so the lion might get more food by working in a pack with other lions. • C This might make the lion more likely to have more or better quality mates, resulting in more offspring or offspring that are more likely to survive. • D Prey less likely to spot the lion waiting to ambush it , so the lion is likely to catch more prey. • E Good at avoiding injury from other lions or prey; better at catching prey such as impala that are very quick moving • F Prey can be quickly killed, avoiding a prolonged chase; the lion wastes as little energy as possible in the hunt and so maximises the gain from the prey it catches Activity 2 (Standard demand) • Row 1:Retrieving wildfowl shot by owner, sometimes over water • Row 2: Border terrier • Row 3: Stamina, striking looks • Row 4: Companion or ‘lap dog’