Archive for November, 2010

what has more energy?

November 11, 2010

Jenna asks:

What has more energy, an unburned log or the ashes of the log once it has been burned?

The wood has more energy. As the wood burn, it releases some of the energy that is stored in the wood – heat, sound, and light are all forms of the energy that is released.

What happens when wood burns is that many of the large complex molecules that the tree made while it was growing get broken down into smaller molecules. This releases energy. Some of that energy is used to break other molecules in the wood apart, and the rest is released to the environment. The reason wood doesn’t just light on fire by itself is because it needs that initial energy to start breaking the first molecules up. Once it’s going, it will keep going until it either runs out of things to burn (in which case it doesn’t have any more molecules that it can break up), or until it cools off enough that there isn’t enough energy to break up more molecules.

How do seeds know when to grow?

November 5, 2010

Joe asks:

why are seeds able to wait for the proper condition to germinate?

Because that’s what seeds do.  Really. Now, HOW they do it, that’s a whole different question…..

Without getting into some fairly complex biochemistry, the answer is fairly simple. Seeds have a whole slew of little biological switches. They are turned on and off depending on the environment that the seed is exposed to. Some of them are fairly simple. For example, if it is very dry, the seed’s shell will stay hard, and keep what moisture there is inside the seed where it belongs – inside the seed. If the outer environment gets wetter, the seed shell will absorb some of the water and get softer. This is actually lot more complex than just soaking up water – the proteins and lipids in the shell actually change shape and go through a bunch of other changes as they absorb the water.

These changes do all sorts of things. When they change shapes, they expose different parts of the proteins to the inside of the seed. When this happens, the newly exposed parts can trigger other reactions inside the seed. Those changes trigger other changes, and if conditions are right, the seed may start to grow.

This is a very simplistic example – all we are looking at is the amount of water int he environment. Temperature, light, nutrients, and a whole slew of other factors can come into play, but the basic concept is the same. If all of these “switches” ‘turn on” (or off) in the right combinations, and in the right sequence, the seed will start to grow.

Sometimes, a seed can “turn on”, then if conditions don’t stay right, they can “turn off” again until conditions get better, but not always. Of course, the longer the seed has been growing, the less likely it will be to be able to return to being dormant. Some seeds are really incredibly good at waiting for the right conditions. A few years ago, a 2,000 year old date palm seed was successfully sprouted, and is still growing. Pretty cool by my book…..

So there ya go. Seeds are basically little environment computers waiting for conditions to be just right  before they launch their “grow” application.

See, science isn’t all that hard if you ask the right questions……