Friday, June 22, 2012
Here is one of the most puzzling questions about the desert; why do cactus have spines? The evolutionary explanation is that they are modified leaves, but why not just lose the leaves altogether? Why long sharp spines? The few animals that eat cactus, eat the spines as well as everything else. But there are precious few animals that eat cactus with or without spines. In fact, almost every plant that grows in the desert, except some grasses and ground hugging plants, have some kind of sharp pointy things growing on them. Why? What possible evolutionary advantage is there to a defensive system for which there is no enemy?