Planet Mad

It's been another good evening on duty in the House. I've done some Business Studies and some Economics (hurrah, questions I could answer!); I helped J prepare for her Spanish GCSE oral exam (although a Spaniard would have killed me for the way in which I murdered the language tonight); and I helped someone with some biology...

Girl: It's no good - I just can't do it!
Me: (Kind, caring tutor mode) Why not? What have you got to do?
Girl: Write something about why leaves give off water.
Me: (consulting the inner-geographer) Hmmm... evapotranspiration, eh?
Girl: That sounds sort of familiar but I can't remember.
Me: Have you got a text book?
Girl: Oh, I'd not thought of that. Here you are...
Me: (flicking though index and muttering under breath) hmmm... page 67... transpiration... stomata... nutrient transfer... diffusion gradient... OK, OK, I think I've got it: are you ready for this?
Girl: Go on...
Me: Leaves give off water because it's the tree weeing!*
Girl: You're not a biologist are you?!

I knew there was a reason that I'm not allowed in science labs; I think I've just remembered it.

* Which technically is true, as the leaves transpire water through the stomata as a way of maintaining the diffusion gradient to suck water (and accompanying minerals) from the soil into the roots. If the trees didn't get rid of the water somewhere then they'd burst. See - it's just like humans weeing, but upside-down: we take water in at the top and it goes out at the bottom; trees take it in at the bottom and get rid of it at the top. Simple, huh?!