The First Requirement of Life; Energy Flows Through the Ecosystem

Energy flows both vertically and laterally through the network of levels of organization that make up the living Creation. The question, of course, is why and how does the living earth ecosystem accomplish this flow of energy. We have already introduced most of the components of this process.

Energy
is the ability to do work. If this definition seem to you impossible to understand, you are understanding. The definition an observational one. We do not see and we do not fully understand energy, but we need the word to describe the processes that we do see, without exception, in the living and nonliving parts of the earth ecosystem — and in the whole universe, so far as we know.

The Second Law of Thermodynamics is a another observational definition of the reality of how the whole of The Creation functions. The whole universe, so far as we can know. The second law says that everything will naturally tend to become less organized on it’s own. Energy can spontaneously convert from a higher to a lower form (nuclear > light > heat), but not the other way. Also physical things can fall apart (because it is energy that keeps them together), but it requires energy to do the work of putting them back together. The rock will roll downhill, fall into the river, and be buffeted about by the water that is running downhill into the ocean, but it requires energy to build a pile of rocks or to carry the water back uphill. So, for our purposes, work is anything that can cause a change from a lower (less organized) to a higher level of organization of energy or of matter. If the second law of thermodynamics seems difficult to understand, it is. But within the ecosystem we need only to understand that energy and matter exist in lower and higher levels of organization and it requires energy to make things more organized.

Life on earth is organized into levels of energy and complexity: the cell, the organism, the ecosystem and the whole earth ecosystem are the major levels of complexity.

Living organisms are able to use the natural flow of energy to do the work that is required to stay alive, but they can not change the laws of thermodynamics (or any other basic law of nature). Basically, living organisms (plants mostly) change light energy into organic energy, in the form of food The plants are able to make larger organic molecules and macromolecules from small molecules.

Energy is required to make something big from something small.

The plants capture light energy from the sun and change the light energy into what we are referring to as organic energy. We define organic energy as the energy of the “bonds” that join together carbon and oxygen and hydrogen and nitrogen (and other atoms) to make organic molecules.. The bonds that join organic molecules are not different from energy bonds that join inorganic molecules, but there is a whole big branch of chemistry that studies energy bonds between and among different kinds of atoms. We don’t need to understand allo the different kinds of energy bonds that function to make big molecules not fall apart, and so I have lumped them all in the category of “organic energy.” For our purposes, we need to know that molecules are held together by energy bonds and bigger molecules contain more energy than smaller molecules. This amazing accomplishment uses the second law. A higher form of energy is converted to a lower form — light energy is converted to organic energy. The higher energy form (light energy) contains more energy than the lower form. Some of that energy is used by plant cells to make the energy bonds of organic molecules and someof the energy is lost as heat.

Macromolecules are large molecules that are composed of molecules that are joined together by energy bonds.

Molecules are composed of atoms that are joined together by energy bonds.

Living things are composed of atoms and molecules and organic macromolecules that are joined together by energy bonds.

Atoms contain energy and matter (matter is the stuff of things that we can see and feel and it has weight if it is in a field of gravity). Again, there is a nice picture book on this subject, by Theodore Gray and Nick Mann, that shows the different elements of which the earth ecosystem is composed. That is, the different kinds of atoms. Everything we know is composed of atoms (matter and energy). The atoms join together to make molecules, and they do this according to energy relationships that depend on the specific matter/energy characteristics of each different kind of atom, that is, the kinds of energy bonds they can form. We do not need to study all these different energy relationships to understand that different atoms are more or less likely to form various kinds of energy bonds, that big molecules contain more energy than small molecules because of the energy bonds that join together the component elements, and that the particular atoms that make up most of the organic molecules are carbon, oxygen, hydrogen and nitrogen. And that plants capture the light energy from the sun and use that energy to join together atoms to make organic molecules.

Our food — also all of our other energy-containing carbon compounds (oil, gas, coal etc) – consists of organic molecules that were made by plants at some time in history. This is why some people propose to use live modern plants to make fuel for our cars.

In fact, the energy that runs all of the living earth ecosystem, comes from organic molecules. High energy organic molecules are circulated through the network of levels of organization of the whole earth ecosystem, first by plants. Organisms that can not do photosynthesis get their energy by eating plants, or other organisms. At every step of energy exchange (whenever organic molecules are eaten or burned) some of the energy is changed to heat and is lost from the system.