Australia has considerably fewer species of carnivorous mammals than any other continent does but about as many carni...

Naz on December 2, 2014

The first sentence of the argument describes an effect: that there are vastly less species of carnivorous mammals in Australia than in any other continent, but around as many carnivorous reptile species as other continents.

The second sentence describes the perceived cause of this effect: the unusual sparseness of Australia's ecosystems.

The third and fourth sentences explain how the cause leads to the effect: carnivorous mammals must eat much more than carnivorous reptiles need to, so they are at a disadvantage in ecosystems in which there is relatively little food.

Thus, the argument is trying to prove that the unusual sparseness of Australia's ecosystems causes fewer species of carnivorous mammals in Australia than any other continent but about as many carnivorous reptile species, i.e. answer choice (C).

Remember, the last sentence is a subsidiary conclusion. Always ask yourself whether the conclusion you have identified helps support any other sentence. If it does, then it is not the main conclusion. The main conclusion will not support any other sentence in the argument.

The last sentence helps support the theory that the unusual sparseness of Australia's ecosystems causes the levels of carnivorous animals to be in the proportions they are compared to other continents.

Hope that clears things up! Please let us know if you have any other questions.

MJA7 on December 2, 2014

Great explanation- thanks!!!