(Intro)

Plants are awesome. They're usually quite pretty. The bigger ones provide shade in the summer, many of them have flowers, and some of them are downright tasty. They even do something that most other living things on Earth can't do. Plants take the energy from the sun and change it into chemical energy through photosynthesis. This is the energy that they use to grow.

I'm sure you already realize that certain plants, like pineapples, only grow in certain places, specifically places that are tropical, warm, sunny and a really nice place to take a vacation. But you don't naturally find pineapples in the same places as you do penguins. But why is that? Why do some plants grow in certain areas of the earth, and not others?

Like so many things, the answer has to do with the sun. The earth orbits the sun every 365 days. It takes this trip tilted on an invisible line called its axis. This tilt means that the sun's light doesn't hit the earth evenly. You know this from when we talked about the seasons and why they happen. But seasons aren't the only thing caused by Earth's tilt. 

Some parts of the earth, specifically near the equator, get a lot of direct sunlight, or sunlight that beams straight down instead of at an angle. Direct sunlight is pretty intense and hot, so the areas around the equator are warm all the time.

Now, the opposite is true for the poles. They get a lot more indirect sunlight, or sunlight that strikes the earth at a shallow angle all year long, and angled rays are a lot weaker, so they're less warm. And this explains why there are no pineapples at the south pole. How?

Let's say you grow two bean seeds in the same conditions in the same room. Same amount of soil, same amount of water daily, even the same kind of pot. Then let's say you put one in direct sunlight, like on a window sill, and the other across the room on the table. And then you wait.

After about three weeks, if you compare the plant grown in direct sunlight with the one grown in indirect sunlight, you'd see that the one grown in direct sunlight is a lot bigger, not to mention happier and healthier, if greenness is any indication. Why shouldn't it be? It's had more sunlight to change its energy through photosynthesis, and that energy means more growth.

And if you compared the temperature on the window sill to the temperature on the table, you'd see that the plant on the table is growing in warmer temperatures, too.

Since the equator gets direct sunlight all year long, it has warm temperatures all year long. So, picky plants like pineapples, which take a long time and a lot of energy to produce that yummy fruit, are able to grow there. But pineapples at the poles, nope. There's just not enough energy from the sun there to give the plant what it needs to survive.

So, the earth's tilt on its axis means that areas around the equator get direct sunlight all year long. This means warm temperatures throughout the year. And the areas near the earth's poles get indirect sunlight all year long, which means colder temperatures throughout the year.

Since plants need sunlight for photosynthesis, areas that get a lot of direct sunlight, like around the equator, are home to lots of plants, especially the ones that take a long time to grow. And that's why there are no pineapples at the poles. So all I'm saying is if you happen to be traveling to the north or south poles any time soon and you really, really like pineapple, you should just plan on packing some with you. Don't say I didn't warn ya!