QUESTION TEXT: Columnist: Contrary to what many people believe,…
QUESTION TYPE: Weaken
CONCLUSION: The number of species on Earth is not declining.
REASONING: New species emerge at the same rate as in past centuries. The rate of extinction hasn’t increased since 1970.
ANALYSIS: The conclusion is that the number of species is not declining. That depends on two things:
- How many new species are emerging?
- How many species are dying?
It’s possible that even in past centuries there weren’t enough new species to replace those going extinct.
That would mean that in 1970 the extinction rate was much higher than the new species rate, and the number of species was declining.
- CORRECT. This is not a strong answer, as it only address one year, 1970. But it does slightly weaken the argument. It shows us that there are not enough new species to replace all the species going extinct.
The conclusion only said that the number of species is not declining. So by showing that the number of species declined last year, this weakens the argument.
- The argument was talking about the entire planet. Individual regions don’t matter – they’re part of the planet.
- The argument was talking about the rate of extinction, not the total. We could have many new species even if most species that existed are extinct – the Earth has been around a long time.
- The argument was about rates of extinction. That’s a question of fact. Public opinion is irrelevant.
- This gives us hope that scientist can prevent some extinctions. It doesn’t tell us how many extinctions are happening.
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