Charlie Sensenbrenner's List: Extinctions, Human Impact, Resources on Earth

For an overview of the magnitude of the crisis, scroll slowly down this page and read just the titles of all of the links. When you finish, go back and begin to click on the links to read the full articles.

New articles are added to this list regularly. Most recent update: January 8, 2013.

excellent online textbook

evolution, adaptation, sexual selection

Excellent collection of images uploaded and geo-tagged by users around the world.

"Evolution Explained For Kids – Mutation And Natural Selection
Posted on July 19, 2011 by biguglyjim
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[This is the second article where I explain evolution in what I hope are kid-friendly terms. Again, my intended audience in this case isn't actually kids, it is parents trying to find ways to communicate with their kids. To see other entries, go here.]

You may have heard the word mutant before, probably in a comic book or in a movie, but did you know that you are a mutant? No, you can’t fly or shoot fireballs, but every one of us is the product of mutations. Life started with really simple things, like amoebas that are made up of only one cell. Everything alive today from your parents to penguins to potatoes started out just that way. But parents are not much like penguins, and even less like potatoes (except couch potatoes). This is because of things like mutation and natural selection.

Sometimes there are errors in DNA. These errors could happen in a bunch of ways, but one of them is when the DNA is making a copy of itself. When a cell splits in two, it creates two complete cells that each have their own copy of the DNA, but sometimes they don’t get the copy exactly right. This means that something is now different in our body’s instructions, and that could mean big changes in how our bodies are put together, but it is also possible that the change won’t really do anything.

Mutations that work are usually really small changes. Imagine that there are a bunch of mice living in the desert. If they are white or black, they are easy for other animals to see, which means they stand a better chance of being eaten. But if a mutation happened in one of the children that caused its fur to blend in a little bit better to the sandy desert, they would be harder to see and may be able to survive a bit better. The longer an animal survives, the more likely it is that it will be able to have babies, and if some of those babies get the same mutation in their DNA, they get that same increased chance to survive and have babies of their own.

This is called natural selection. Nobody is thinking, “Gee, we should color the mice more sandy so they live longer”. It isn’t a decision anyone is making, it is just a matter of other animals who might eat the mice not being able to see them. If a bunch of eagles were hunting and could only see the white and black mice, then it would be a lot harder for them to live long enough to have babies. And if they don’t have babies, they aren’t passing on their DNA.

Now, that’s a tiny example just to show you what I mean. But here is a bigger and better one. Have you ever heard that we came from monkeys? Well, that’s not exactly true. Scientists would say that we share a recent ancestor with chimpanzees and bonobos, but what that means is that if you go back in time, you would find something that looks a bit like a lemur, and one of those had babies that had babies that had babies all the way until you get to us. At the same time, other of their babies had other babies that had other babies all the way until you get to chimpanzees. So why don’t we look like chimpanzees or lemurs?

It’s because of natural selection. What natural selection means is that the animals that get to have babies are the ones who are best able to live longer and healthier lives. If some of the children from that lemur-like ancestor of ours got separated from the others and wound up living in a place that had a different environment, then what would make them have the best chance to survive might well be different. Those mutations and changes between the two families would be different, and over millions of years, we wound up being very different than our distant cousins the chimpanzees.

From those very first single celled life forms, mutations and other little changes have had billions of years to slowly progress as living things tried to stay alive and have families. All the living things on earth in all their amazing different forms have evolved from the smallest of creatures."

awesome resource including great lessons, powerpoints and links to the ARKive web resource