A Speaker's Reasons and Evidence
SL.4.3
Read the text, then answer the questions.
The Wolves and the Rivers
Wolves were shot out of Yellowstone by 1926. Fourteen were brought back in 1995. With no wolves, elk had grazed the valleys freely for seventy years. Young willow and aspen were eaten as soon as they grew. The wolves killed some elk. More importantly, they changed where elk would stand still. Open valley floors became dangerous, so the elk stopped lingering there. Willow and aspen grew back along the rivers. Beavers, which need willow, returned. Their dams made ponds. Roots held the banks. The rivers narrowed, deepened and moved less. Some researchers describe this as wolves changing the shape of rivers, though others argue the effect has been overstated.
- 1. Quote the words that explain the wolves' most important effect.
- 2. The author reports a disagreement. What is it, and how is it presented?
- 3. What is the author's purpose, and how do you know?
How Penicillin Was Found
In 1928 Alexander Fleming went on holiday and left a stack of dishes on a bench. Each held a colony of bacteria. When he came back, one dish had a spot of mould on it. Around the mould was a clear ring where the bacteria had died. Fleming realised the mould was producing something that killed bacteria. He named it penicillin and published a paper. Almost nobody noticed. Ten years later, Howard Florey and Ernst Chain read that paper and tried to make penicillin in quantity. That turned out to be the hard part: it took two thousand litres of mould fluid to treat one patient. By 1944 the problem had been solved and penicillin was reaching soldiers in the field.
- 1. Quote the sentence that explains why Fleming's discovery went nowhere at first.
- 2. The text says the hard part was not the discovery. What evidence supports that?
- 3. What is the author's purpose, and how do you know?
LessonPrint · SL.4.3 · Set 15 · free to copy for classroom use