Just the Right Size written by Nicola Davies, illustrated by Neal Layton, 60 pp, RL 4


Nicola Davies is a zoologist and her author bio is so great I have to quote it in full here.  Of her passion, she says, "In the wild, I've seen dwarf chameleons smaller than my little finger and blue whales bigger than my house, and I couldn't say which is more thrilling. I'd love to see the world's smallest mammal - the bumblebee bat, which is the size of . . . yes, a bumblebee. Imagine how small its babies are!"  This kind of fascination with the world that she writes about seeps through her wonderful non-fiction books for children, three of which are illustrated by the super Neal Layton.

With Just the Right Size: Why Big Animals Are Big and Little Animals Are Little, Davies focuses her animal expertise on, as the subtitle tells us, "Why Big Animals Are Big and Little Animals are Little." 
What this boils down to is, why can't humans (and other large creatures) fly and why can't small (or even regular size creatures) grow to be enormous. Why isn't there a King Kong or a Superman? Davies posits the BLTL Rule, or, the Big Thing Little Thing Rule which states that, "If you double the length of something, its surface area and cross section go up FOUR times, while its volume and weight go up EIGHT times! She demonstrates this with some very cool fanged cubes and tells readers that the BTLT rule "stops monsters such as car-sized spiders from existing in the real world, and it also means that humans can't list busses and could never flap their arms and fly." 
Davies goes on to talk about why humans can't fly or walk on water, how geckos walk on the ceiling and why humans can't lift busses. She moves on to size in the animal world, pointing out that, for a 100 foot long blue whale to double in size, its internal organs would have to supersize at such a rate that they would not fit inside the body of a 200 foot blue whale.
This leads to a discussion of "Rules on the Inside" and why a single-celled creature couldn't get very big.   Examination of internal organs, including a fascinating look at the different kinds of lungs and what they allow various creatures to do. Davies shows the reader that big is complicated and that being tiny is tough. Her look at ants and other small insects and just how dangerous water is to them (thus necessitating "long, strawlike mouth parts so that there's no risk of any other bit of the body getting wet" was the most fascinating piece of information to me. She writes that a "film of water around a wet, ant-sized body can weigh many times more than the ant does, making it hard for small animals to move when they get soaked. What's more, the surface tension of the water acts like a wrapping of stretchy cellophane, trapping the animal inside, so it may even drown!"

What I love most about this book (a very close second being Layton's engaging illustrations) is the way that Davies shares this information, which is sometimes almost too much to grasp, in a completely entertaining, conversational manner that makes this VERY scientific book feel and read like a picture book! Which is good, because I think it's a pretty solid third grade reading level. And, while many third graders will be interested in Just the Right Size: Why Big Animals Are Big and Little Animals Are Little, many younger non-readers will find it fascinating as well!

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