Introduction to Middle school biology | Khan Academy

Hi everyone! Sal Khan here and welcome to middle school biology. I have Iman Howard here who manages our STEM content. Welcome, Iman!

And why should folks care about middle school biology? Biology is the study of life and so in this course, it really answers: Why are things the way they are? Why do you look the way you do? Why do I look the way I do? And how every organism on Earth has a really special purpose and a special trait.

Based on these traits, it helps them interact with their environment. We even talk about energy, and energy can't be created and it can't be destroyed. It actually cycles as matter through an ecosystem. It even has these really cool chemical reactions called photosynthesis, where plants use light energy from the sun and they make their own food, which is insane.

Think about organisms like the gorilla that are super big and strong, and they don't go and eat a cow; they go and eat plants because that's like getting energy right from the source. And then finally, we talk about evolution. Based on our traits, how have we changed over time?

How some of our natural traits were selected by the environment that created those changes? Or even how humans—we have something called artificial selection, which explains why your dog's so cute, whether it's a hundred pounds or five pounds—we did that.

What do you think is cool about it, Sal?

Oh well, biology is trying to enter. I mean, to your point, the questions of life, which we still don't understand a lot about. But like, what makes us us? And to realize that we aren't—we don't exist as human beings in isolation.

We're part of an ecosystem; we're part of a story, a narrative that's been going on for millions and billions of years. The fact that we're made up of trillions of cells, each of them with DNA that can describe who we are. How did all of this complexity come about?

This is maybe the most mind-blowing topic that we're really at just the beginning of this journey. So I think folks are going to be really, really excited to—it's going to be really interesting to see all the things that they get to learn. Dig in!