Hopefully by now, you realize that our world
is always changing.
Land forms change, weather changes, even molecules change.
With all of that change going on, living things had better be able to keep up.
And they do.
When the world around them changes, living things change too, sometimes in a big way.
So what can happen to living things when the world around them changes
You may recall that once upon a time we talked about pineapples, and we said they were picky
because they can only grow in lovely, lush,
tropical climates.
No pineapples at the poles, right?
That's because the environment at the tropics is perfect for growing pineapples.
An environment is made up of the conditions around a living thing.
Now that might sound kind of like the definition of the word ecosystem,
but the word environment is usually used to talk just about non-living things in an ecosystem,
like temperature or the amount of rain or even how much pollution there is.
So while the environment at the poles isn't great for growing pineapples, it suits other living things just fine.
Like penguins in Antarctica or polar bears
at the North Pole.
If we put these animals into a pineapple field, they'd get pretty hot and unhappy.
That's because they have adaptations for the cold.
An adaptation is a characteristic that helps an organism live in its environment.
But sometimes, when an environment changes,
it upsets the delicate balance of the food chains in an ecosystem.
For example, about 360 million years ago,
the Earth looked a lot different than it does now.
The Earth was much warmer and the land was covered with lots of forests and swamps.
And the animals that lived then?
Let's talk about centipedes that were 2 meters long, amphibians that were 6 meters long,
and dragonflies that were the size of large
birds.
Clearly none of these creatures are still
around, so what happened?
The environment changed.
Over several million years, the climate became drier and cooler
and many plants didn't have adaptations that help them survive in this
new, cool, dry environment,
so they became extinct.
And that was a problem.
Plants are at the bottom of the food chain.
They make chemical energy through photosynthesis
and then they release oxygen.
All of those plants made lots and lots of
oxygen.
There was more oxygen in the Earth's atmosphere
than than there is now, enough to support all of those giant insects.
But when those plants became extinct,
the animals that depended on all of that oxygen could no longer survive.
Ciao giant insects!
And the amphibians and other animals that ate those insects had less food,
so they didn't do much better.
See you, giant amphibians!
But let's take a look at how adaptations can help a living thing fit into its environment
using another, smaller insect.
Meet the peppered moth.
Cute, right?
And it comes in two types: light and dark.
As you can probably tell, the dark colored
moths are a lot easier to see when they're resting on trees,
and easier to see means
they're more likely to become snacks for birds and other predators.
That means the light moths have an adaptation that helps them live in their environment.
So if we went through the woods looking for moths, we'd expect to catch more dark moths than light ones.
Now, what would happen if the environment changed?
It did, true story.
A couple hundred years ago, people started burning a lot of coal for fuel, and this made a lot of pollution.
The pollution coated the trees, turning them dark with dirt and soot.
The dark moths now had the adaptation that helped them fit into the environment.
They blended into the trees which were dark, too.
The moths that were lighter though, not so lucky.
In the polluted environment they didn't fit
in as well, so they got eaten more than the dark moths.
The dark moths that lived reproduced to make more dark moths.
The results?
After the environment had been polluted for a long time, there were more dark moths than light ones.
Fortunately, we've gotten to be a lot smarter about pollution.
Over the last 50 years, the environment has changed from being more polluted to less polluted
and the trees aren't covered with dark dirt
anymore.
As you can see in this diagram, the number of light-colored moths is on the rise.
All living things have characteristics that
help them to fit into their environment called adaptations.
If the environment, the conditions in which something lives, changes, then the living things change, too.
The living things might gain different adaptations that help them to survive in the new environment,
or the result might be more severe and affect the whole food chain.
But more on that next time.
