What living things can be seen from space?

I'm guessing that you mean the Great Barrier Reef, although I really don't see it as "living."
It is a construction made by living things, who then inhabit it. It's no more living than a house of skulls constructed by people.
While I'm not sure how far up 'space' begins, I know it is much closer than most people think. It may be possible to see herds of whales, and I imagine that, a century ago, one could have seen herds of springbok, herds of buffalo, and flocks of birds from space, were one able to get there.

The Great Barrier Reef is also considered the largest organism in the world, isn't it? But I agree, the "living" part is debatable.