Since animals emerged on land more than 300 million years ago, they've turned to plants as a source of food. But despite deploying their best modes of attack, surprisingly, animals only manage to eat around a fifth of the vegetation that’s available to them. So why don't they eat more?
In her first lecture of the series, Sue Hartley explains why animals have a harder time than we think when it comes to eating plants, whilst Adam squirm as he eats the world’s hottest chilli.
Just like humans and other animals, plants need to communicate, particularly when they are under threat. But although these chemical defence mechanisms might save them from being eaten, it uses up vital energy that could otherwise be used for growth.