Now that's one of those questions like "why is the sky blue?" or "who is the fourth president of the United States?" that you'd think you'd know the answer to right away, and then quickly realize that you're not one hundred percent sure if you're making it up or if you're pulling it from an accurate file from long ago.
I answered "I think probably because most likely they need them because it seems like they need them for protection." Yeah. That's it.
"Well, maybe we should look it up when we get home," Po suggested.
"Great idea. Let's do that." Here we go. Outsmarted by Po, once again. There's no satisfying him with a half-assed answer. I thought for a few moments, and then said "you know, Po, now that I'm thinking about it, I bet they really do have spikes to defend themselves."
He elaborated for me. "Oh, yeah. Like from predators who want to eat them. Like the piranha."
"I'm not sure the piranha is a threat to the cactus."
"Well, piranhas can be really snappy things that are really snappy when you try to save the life of something that they are trying to eat. They'll eat anything, you know. And they don't want to not eat the thing that you're trying to save. They're really snappy."
"Wow. You know a lot about piranhas, Po."
"Yep. So cacti have spikes to protect them from predators, like the piranha," he concluded.
When we got home, I looked it up. Wikipedia says: "In most species of cacti the leaves have evolved into spines which not only defend the cactus against herbivores but also provide shade that lowers the plants water loss through transpiration."
Po's response? "Oh, yeah! Herbivores! Herbivores are predators to cacti."
Folks, that concludes today's lesson.
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