Great Question, Josiah!

Josiah, a frequent commenter on this blog, asked an excellent question in a post on my previous entry. I started to reply to his question, but I realized the answer would make a good blog entry. Josiah asked whether or not “cooperative relationships in the animal world” are a problem for evolution. He doesn’t think so, but the author of one of his homeschool books thinks it is. What do I think?

Well, let’s start with the terminology. A relationship between two or more individuals from different species is called symbiosis. However, that word has grown to refer to different kinds of relationships. It can refer to a relationship in which all participants benefit, a relationship in which only one participant benefits but the others are not harmed, or a relationship in which one benefits and another is harmed. Thus, to specifically talk about cooperative relationships, we use the term mutualism, which refers specifically to a relationship in which all participants benefit.

Josiah mentioned a couple of examples of mutualistic relationships. One was the tick bird, which eats ticks off a rhino’s skin. This is beneficial to the rhino, which becomes relatively “tick free,” and it is obviously beneficial to the bird, as the bird has a fairly safe place to find food. The tick birds also warn each other (and the rhinos) about any incoming danger. The other example was the single-celled protistans (flagellates) that live in a termite’s gut and digest cellulose. The termite (indeed, all multi-celled animals of which I am aware) cannot digest cellulose on its own, and since wood is 50% cellulose by mass, this would be a problem for an animal that eats wood. However, the flagellates in a termite’s gut digest the cellulose, which allows the termite to eat wood. Obviously, both participants benefit in this relationship. Are these kinds of situations a problem for evolution?

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Lobsters Aren’t So Stupid After All!

My grandparents lived in the wonderful little town of Ipswich, Massachusetts. My family would visit them nearly every summer, and I loved it. It was right near the beach, and the seafood was amazing! I remember the first time I saw this kind of device there:

An unlucky lobster in a "trap"
(Photo licensed through www.clipart.com)

I asked my parents what it was, and they told me it was a lobster trap. I was skeptical. After all, it was just a wooden cage with some netting, and the netting had a big hole in it. I asked my parents how it could trap anything. After all, if something could crawl in the hole, it could crawl right back out again, right? My parents told me that lobsters were too stupid to do that. They would crawl in the hole to get the bait inside, but they would not know enough to back out of the hole, and since they couldn’t turn around in the small enclosure, they would end up being trapped. I remained skeptical, but I asked lots of people in that small New England town, and they all gave me the same story my parents gave me. After all, it was “well known.”

Of course, science has a way of telling us that lots of “well known” things are 100% incorrect!

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