Unit 14
How animals live.
Whole animals in the world: how they raise young, change body, eat, move and flock, and what each costs in energy.
Before this unit
The unit, lesson by lesson
Lessons
5 lessons · 29 practice questions · about 2 hours
Broods and care
Four mothers and two bets: a million cheap eggs left to chance, or a few young looked after. External and internal fertilisation, one budget shared out, and why about one or two from each brood grow up.
A new body
One animal, two bodies: a caterpillar that grows in jumps inside a skin that will not stretch, a chrysalis in which most of the body is broken down and rebuilt, a tadpole whose tail is absorbed into the froglet, and the hormones that decide when.
Built for their food
Five heads and five foods: a cow grinding grass from side to side, a cat shearing meat with scissor-like teeth, a whale sieving krill through baleen, a hummingbird lapping nectar with a forked tongue, and guts that lengthen when food is hard to digest.
Push back to go forward
A dog, a trout and a pigeon move in place in a lab: each pushes the ground, the water or the air backwards and gets an equal push back. A walk that turns into a run, feet that push harder than the weight, and what a metre costs on land, in water and in air.
Moving as one
A starling flock with no leader: each bird applies three rules, separation, alignment and cohesion, to its seven nearest neighbours, and the shape of the whole flock emerges by itself. What happens when you switch a rule off, and why the same happens in fish, ants and crowds.