Elizabeth, a Licensed Massage Therapist, has a Master's in Zoology from North Carolina State, one in GIS from Florida State University, and a Bachelor's in Biology from Eastern Michigan University. She has taught college level Physical Science and Biology.
We All Need Energy
Believe it or not, your existence here on Earth depends almost entirely on one thing: the sun! Yes, you need to drink water and eat food, but those things wouldn't be here either if the sun weren't shining on us. The sun sends photons to Earth, which are tiny particles of light. These photons are what drive photosynthesis, the process of converting sunlight into usable, chemical energy.
You don't have to be a vegetarian to appreciate how important photosynthesis is. Even if you only ate meat (though you really should listen to your mother and eat your vegetables too!), the animals you are eating either ate plants or ate other animals that ate plants. So without plants there would be no energy for the rest of us, but without sunlight, there would be no plants!
Matter Is Exchanged
Can you see how all living organisms need free energy and matter to, well, live? Not only do we require free energy and matter, but the world needs us to exchange this with our environment on a regular basis.
Molecules and atoms that currently exist in the environment will eventually be used to make new ones. When a living organism dies, its body gets broken down into its molecular parts, and these molecules can then feed new plants and animals that are just beginning to grow.
There are a few major players that most organisms need to sustain life. Carbon is by far one of the most important because this is the basis for all organic material. Carbohydrates, lipids, proteins, and nucleic acids are all made of carbon, and you need all of those to survive!
Nitrogen is also important, and this comes from the atmosphere. In fact, most of Earth's atmosphere is made of nitrogen - about 79%. Nitrogen is also instrumental in building proteins and nucleic acids, both of which make up your DNA.
Phosphorous is not only helpful in making soda, but more importantly, it is a vital nutrient to plants and animals because it is a key component to DNA, which is what makes you 'you'! Phosphorous is one of the most abundant minerals in your body and is essential to cell division and growth.
You likely already know that water is essential to living organisms. Water is pretty amazing stuff and has some unique properties that allow life to exist on Earth. Your body is made of mostly water, which helps your blood flow, your cells divide, and your organs function properly.
Energy Is Captured and Stored
Cycling energy and matter through the environment means that there is no loss or buildup on Earth. But we do temporarily store these things in our bodies and use them to drive biological processes while we're alive.
Plants do this through photosynthesis, and because they make their own food, they are called autotrophs. This means that they are self-feeders, just like 'auto-pilot' means 'self-driving'. We can't turn sunlight into usable energy ourselves and, therefore, depend on other organisms to provide us with food. This means we are heterotrophs, or other-feeders ('hetero' means 'other').
There are a number of processes that occur in our bodies to harvest energy from matter. During cellular respiration, we harvest energy by breaking down carbohydrates. This is done through processes like glycolysis and the Krebs cycle, which eventually turn those sugar molecules into energy called ATP. ATP is an essential molecule - without it, livings things cease to live.
Organisms use free energy for many other things, such as growth and reproduction. For example, your body's temperature and metabolism depend on you taking in free energy and matter. It also takes a lot of energy to produce and rear offspring. A good example of this is birds, many of which search for food and bring it back to their young until they can fly off and get their own.
And what about hibernation? Animals like bears and bats that spend their winters in such a state need to store up energy so that they don't starve to death during these hibernation periods. Eating just enough to get by for a day or two won't cut it when you're not planning to eat for the next several months.
Changes in Free Energy
When the amount of free energy that is available changes, this can cause changes in everything from small organisms to entire ecosystems.
On an individual level, if you do not have enough free energy, you go hungry and eventually waste away. However, if you take in too much (like at Thanksgiving dinner), you store that and your body grows. When you're a kid, you tend to grow upward, but as an adult, well, we tend to grow outward!
Changes in free energy can also have larger scale effects. Imagine that all the producers in an ecosystem, which are the plants that produce energy for other organisms, are suddenly removed. Or that the amount of sunlight is decreased so that photosynthesis decreases as well. What do you think would happen to the organisms that depend on those producers for food? They would probably all die since there is no production of usable energy for them! This example is a bit extreme, but you can see how changes in just one trophic level may drastically affect the rest.
All living things require a constant input of free energy and matter in order to survive. This energy ultimately comes from the sun as photons, and this sunlight then gets converted into usable energy by plants during photosynthesis. Because they are self-feeders, plants are called autotrophs. We either eat plants and take in their energy and matter or we eat other animals that have eaten the plants. This makes us heterotrophs, or other-feeders. When organisms die, their organic matter is broken down and used again, and in this way, energy and matter are recycled on Earth.
While we are alive, we capture and temporarily store energy in our bodies to drive cellular processes, metabolism, reproduction, and a wide variety of other activities. Small changes can lead to big effects, though, both on an individual level and on the ecosystem level. Taking in too much energy will lead to more storage and weight gain, while eating too little will cause you to wither away and die. Changes in the availability of producers affect each trophic level above it since we all need plants for energy, whether we eat them directly or not.
When this lesson is over, you may be able to:
- Understand the need and use of free energy in living systems
- Recognize how water and the sun's energy is used in living things
- Identify the various ways plants provide free energy
- Recall the storage of energy by living things for survival
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