Bare Bones Biology 035 – Limiting Factors

Last time we did a flash review of the information we’ve covered in this series, and it’s pretty much what we need if we decide we really want to save our ecosystem for future generations, except for one thing I haven’t yet put on the radio, the blog, or the book, and that is the concept of limiting factors. Because it’s so difficult to explain without a blackboard. But it’s also very important.

Limiting factors are those conditions that prevent any population from growing beyond the ability of the ecosystem to support it, and they come in levels, or layers, so the first limiting factor that a population might face – every organism is somewhat different, and that’s why we have so many organisms. They all live in different niches of the ecosystem that have different requirements for staying alive. Anyhow, let’s make one up. Suppose it’s a mouse living in Texas and the first limiting factor is water. I mean a species of mouse, not one individual mouse. So this mouse species can not live in areas where there is not as much water as it requires. Also, as global warming increases, the amount of water will be less and there are fluctuations year by year. The mouse population is responsive to all these changes, mostly in terms of how many babies they can raise in any given area and year. The mouse can’t raise babies in areas that have not enough water. For humans, up to now, we have taken care of the water problem by building dams and water pipes.

But back to the mouse, supposing there is enough water, but the temperature limits the number of mice in any area. We humans make heaters and air conditioners.

So maybe all the conditions were great for the mouse one year and they raised a skizzilion babies, until they are so crowded that a disease spreads through the whole population and wipes out half of them. Humans invented flu shots.

Mouse populations are constantly balanced against the predator populations. If there are five different species that eat mice, then there is a constant balance of both the predators and the prey so that the predators never eat all the mice and there are always enough mice to eat. Unless something changes, and then the numbers of predators will be affected. Or the numbers of mice will be affected, or more likely both. All these things are limiting factors. People have learned to grow their own food. Cattle. And corn. And the like.

But the bottom line is that every living cell and organism and ecosystem requires food energy to stay alive. Therefore, bottom line limiting factor is food energy. Food energy is made by photosynthesis in plants and green bacteria. If the major food of mice is a particular kind of grass seed, and if the mice become too populous, so that they eat up all the seeds, then all the mice will starve, and so will the predators. Human technologies can increase efficiency, but there is nothing humans can do to change the bottom line fact, and that is the limiting factor we now face. Or actually we are not facing it, because we’ve gotten a bit big-headed. We’ve used technology to get around all our limiting factors for all these millennia up to now, and we’ve forgotten that the only reason we could do that is because the earth was making more food than we needed to feed ourselves and our machines and now our corposystem.

But we have now reached the point where we and our machines and our corposystem are all competing with the ecosystem for food energy. Another thing we sometimes forget is that the ecosystem is not growing that food just for us; the ecosystem needs food for all its populations of millions of organisms because they do the work that the whole ecosystem needs to stay alive. So we need to pay attention to the fact that we have hit the bottom-line limiting factor for human beings on this earth. What we decide to do about this situation will determine whether or not we survive as a species, and how many people must suffer for our big-headedness. My point in doing all this work is not to change or control anything about reality, but to honor the humane imperative that tells me less suffering is better than more suffering.

Whatever happens, our populations will not grow beyond this final limiting factor because no technology can change the second law of thermodynamics.

Whatever happens, our populations will not grow beyond this final limiting factor because no technology can change the second law of thermodynamics.

Bare Bones Biology 035
KEOS 89.1, Bryan, TX


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