Life Is

Life is the innate, internal ability to respond to the environment rather than just sit there and be destroyed by it. The flow of information sustains life because it senses the environment and cues the living response. The hand on the hot stove is a reasonable example of this process, but very limiting as a concept because we need the whole of the ecosystem information system to stay alive — in addition to our own nervous system.

Life at any level is maintained by:
1. Flow of energy
2. Recycling materials
3. Flow of information that maintains the balance among all these things.
4. The ability to balance all of the above.

To visualize the flow of information through the whole ecosystem, we need to imagine the functions of the various species of organisms within all the smaller ecosystems that make up the whole. Textbooks often use a pond ecosystem as an example, because it is easier to imagine than a gigantic whole that has no inputs or outputs. Ponds, of course, are in contact with land and air, which helps them to keep their balance. The whole earth has no such buffer to help her maintain herself in space.

But here is the pond, and lets take only four species of organisms. An ecosystem with only four species could not possibly maintain a balance, but let’s pretend.

A water weed
A plant-eating bug
A bug-eating animal
A fungus that eats dead things.

The sun shines on the green water weed. It’s job in the ecosystem is to use the energy from the sun to make organic molecules by photosynthesis. It uses carbon dioxide and oxygen to make organic molecules. It uses the energy contained in the organic molecules, and also the carbon and oxygen, and nitrogen that its roots bring from the bottom of the pond, to make the cells of its own body. The plant also does cellular respiration. So the plant is very important to the life of the pond. It has made organic molecules using energy from the sun, nitrogen from the earth and carbon dioxide from the air. It breathes out more oxygen than it takes in. The plant “knows” how to be a plant because of all its genes that work together to cause all the right functions to happen in the right cells at the right time of its development.

The plant-eating bug eats the plant and uses the energy from the organic molecules, and also the carbon and nitrogen and oxygen to make the cells of its own body. It breathes in oxygen to do cellular respiration and it breathes out carbon dioxide, because all the energy for it to stay alive comes from the process of cellular respiration that breaks down the organic molecules of plant that the bug ate. The animal “knows” how to eat plants and also how to digest them and how to make its own cells because of all its genes that work together to cause all the right functions to happen in the right cells at the right time of its development.

The bug-eating animal eats the plant-eating bugs and uses the energy from the organic molecules, and the carbon and nitrogen and oxygen, to make the cells of its own body. It breathes in oxygen and breathes out carbon dioxide and for all the work of staying alive it uses the energy that was stored in the organic molecules of the bugs that it eats. The behaviors of this animal are also directed by all its genes. It “knows” how to catch bugs and also how to digest them and how to make its own cells because of all its genes that work together to cause all the right functions to happen in the right cells at the right time of its development.

All of these organisms die and defecate, and fall to the bottom of the pond, where the fungus digests the remaining organic molecules, releasing the nitrogen back to the soil and more carbon dioxide into the water. It uses the energy that was stored in the organic molecules to do the work of staying alive, until all or almost all of the organic molecules are broken down and there is no more energy available until some other organisms in the pond defecate or die. Even the fungus “knows” how to do what it does because of the genes that control whatever enzymes and other proteins are produced in its body at the right time and in the right place.

So there are three reasons for explaining this tiny ecosystem to you:

1. Such an ecosystem could not survive for very long because there are not enough different kinds of organisms doing all the jobs. For example, think what would happen if the environmental temperature changed so that species of plant could not survive in that pond. The whole system would crash. The more different species are doing the same or similar jobs, the more likely the pond is to stay alive. This is what Rob Hopkins refers to as “resilience.” It is essential to survival of an ecosystem that it maintain a balance among hundreds of different species that have similar functions but slightly different genomes, so that some of them may be able to survive if the conditions change.

2. Do not imagine that these are the only functions necessary for an ecosystem to survive. Another reason why many hundreds of species are required to do the job of maintaining balance in an ecosystem is that there are many hundreds of different jobs to do. I only listed four basic jobs. Energy flow, recycling of carbon and oxygen and recycling of nitrogen. Many hundreds of molecules need to be recycled, and many hundreds of species are required to ensure the proper flow of energy to every portion of any ecosystem so that the whole may stay alive.

Ecosystems can die.

3. Notice it is the behaviors of the organisms that direct the flow of energy and the flow of materials through an ecosystem. Behaviors of organisms are controlled in large part by the genome of the organism, that is all the genes in the organisms. The gene pool of the organism is all the genes in a particular species. The gene pools of all the organisms and all the species in an ecosystem ARE the flow of information through the ecosystem. Again, Rob Hopkins is correct that the resilience of any ecosystem is much greater, the more variation there is in the ocean of all the gene pools of all the organisms in that ecosystem. Just in case some change happens in or around the ecosystem, if there is a lot of variability in that ocean of genes, then it is more likely that the ecosystem can survive, because it is more likely that some organisms will survive that are required to do all the jobs of energy flow and materials recycling.

This IS evolution.

It is simply silly to argue whether or not evolution exists. Evolution is one of the most important laws of nature, along with gravity and the first and second laws of thermodynamics and the law of cause and effect, that the Creator gave to The Creation so that it can exist. If there were no evolution there would be no life on earth today.

Evolution is NOT survival of the fittest individual within a species. It is survival of a species that helps and does not harm the balance of jobs that are required for the whole ecosystem to stay alive.

The Spirit of God

“In the beginning God created the heavens and the earth. The earth was without form and void, and darkness was upon the face of the deep; and the spirit of God moved over the face of the waters.”

That’s my favorite quote from the Bible.

It doesn’t say exactly how He did it. But here we are in this very fine Garden of Eden, the only living thing within light years, in the midst of a universe of fire and ice. It is indeed miraculous. If a miracle is something that our little pea brains can’t understand, then we are surrounded by miracles and it would be better that we don’t forget it.

Whether or not we can feel the spirit of God moving among the miracles, and even though nobody understands everything, we do know some of the basic natural laws that keep this life alive. Werner von Braun, who I think was a physicist, said: “The universe is hostile only when you do not know its laws. For those who know and obey, the universe is friendly.”

So how do we get to know its laws? I expect he was thinking about the laws of physics, and I expect he was right. We would not get very far trying to pretend we can walk on clouds (even though it makes you want to try sometimes, looking down on them from an airplane) and we wouldn’t get very far without wheels and combustion and all of that kind of technology based in the reality of natural phenomena. And we won’t get very far pretending that life can exist in absence of what it needs to be alive. The word of man is not more powerful than the works of God that lie all around us and proclaim themselves for us to see and understand. And obey — or not. We have the freedom to choose — and as we continue to choose unwisely, the universe becomes more and more hostile.

We are even pretending that we don’t need what we do need for life to stay alive. Right now we need the ecosystem to stay alive. How can we not understand that the ecosystem is a living thing with all the needs of living things? I don’t know the answer to that question, but let’s talk about the needs of all living things. The natural laws of being alive. Boiled rigtht down to the bare bones, they are threefold, and they are the same for the tiniest cell as they are for you and me and for the whole great earth ecosystem that you can see from the moon. If you were foolish enough to go to the moon.

We need food because it requires work to stay alive, and there is a universal law of energy that says no work can happen without energy. We get energy to stay alive from our food. Food does not come from supermarkets or from the sun. It comes from plants, that is from our garden of eden. Once we have eaten the food — we can’t eat it again. Actually we could, but most of the available energy has already been used from the food by the time we defecate it, and energy does not recycle.

We need to recycle materials such as oxygen and carbon dioxide and nitrogen and carbon and all the elements that are part of life. That is another reason we eat. Also it’s why we breathe. And to direct all these activities, every kind of life needs to have the information available that tells it how to use the energy, by digestion and all that, and how to recycle the materials, for example by breathing, in order to stay alive.

All processes require information. We do the processes — we do everything that we do because of our genes. Our genetic code. We can be alive because our genetic code knows exactly when and where to make an enzyme to digest the meal we just ate, and exactly when and where to make a nerve cell or a pigment cell or a muscle cell, or exactly how to think.

These three things — energy from plants, the recycling of elements and compounds, and the genetic code to direct all the whole processes — these are required by every living thing, from the tiniest prokaryotic cell to the entire whole ecosystem itself.

How do we know this? Because without any one of them, life ceases. We do not know everything about anything, but we know that — if God created life — then that’s how he created it to be.

Energy and Information Drive the Cycles

It’s not easy to think about levels of organization as real things. It’s much easier to think of ourselves as real and everything else as a thing, but in fact we are only one cog in the wheel of life — from the life of a cell that perhaps makes up part of your body to the interacting behaviors of organisms, from plants to animals to fungi and other organisms that all interact to spread the food of life throughout the ecosystem.

What would it feel like to be an ecosystem? Or a cell? We can’t know things like that; the only thing we can know is what it feels like to have a brain. They don’t. But we do have the advantage that we can use the brain to figure out what we should do or should not do if we want to stay alive. One thing we should do is to think about our relationships with the other parts of the creation. If we believe in God, then it is a certainty that these other parts of the creation were put here so that we could survive and thrive; if we don’t believe in God, these other parts of the creation are still necessary for our survival. If we want to survive, then, the God question is not nearly as important as the responsibility question. If we only think about what we want today, we have now enough power to throw the ecosystem off balance forever. That’s what the scientists mean by the “tipping point.”

We talk about the tipping point as though we could see it or measure it. We can not. If you were a scientist, you might say: “We don’t want to do that experiment.” It’s no different from experimenting with human lives. Why on this living earth would we want to “wait and see what happens” before we do what we know is necessary to our survival into the future of life on earth?

So let’s try to think about levels of organizations again, and how they relate to the flow of energy and the cycling of materials through the ecosystem, and the flow of information through space and time. Because those are the three requirements for survival of any living thing. Materials recycle, energy flows throughout, information directs all the processes through time.

Let’s begin with the materials that cycle through the whole, because that is relatively easy to imagine. Materials are made of atoms. Atoms are the basic units of elements, or you could say the basic units of matter. Elements are the building blocks of matter. Molecules are made of atoms. Your desk is made of atoms and molecules. If your desk is wood, it’s made of organic molecules. If your desk is metal, it’s made of inorganic atoms and molecules . The difference is the organic molecules are carbon based and were made by trees.

Wood is mostly cellulose. Cellulose is a carbohydrate that was made by a tree using energy from sunlight to bond together carbon, hydrogen and oxygen atoms in a particularly strong configuration. If you burn up your desk, that sun energy is released as heat, the carbon atoms combine with oxygen from the atmosphere to make carbon dioxide, and the hydrogen atoms combine with oxygen from the atmosphere to make water (or actually steam at this temperature).

We do not eat wood because we can’t digest wood. That is, our bodies do not have the necessary enzymes to break apart the molecules of cellulose. If you eat sawdust, for example, it will come out pretty much as it went in. But if you eat a potato that is made of other kinds of carbohydrates, it gets all broken up in your gut into glucose molecules, and then the glucose molecules are transferred from the gut into your blood and they are pumped around your whole body so that every cell in your body has some glucose to burn. Just like you burned your desk, except the cells are able to burn the glucose ever so slowly and capture the energy to do the work of staying alive. The work of staying alive is mostly making other kinds of molecules. All of that is controlled and directed by your genes. Humans don’t have genes that will direct the digestion of sawdust. Quite a few different kinds of organisms do. They can digest sawdust and recapture the energy that is in wood and use it as food to stay alive.

Why do we not have the enzymes to digest sawdust? Enzymes are proteins. For every different kind of protein produced in a living body there is a genetic code. The human genome (all the genes) is not set up for us to eat wood. However, there are genes in fungi, for example, that do make enzymes for digesting sawdust. In the entire ecosystem, there are genes that permit every function that is required for the flow of energy through the ecosystem. This is necessary for keeping the entire ecosystem alive.

Think what happens if you cut off the flow of blood to one part of your body so it can not receive the glucose or the oxygen it needs. That same sort of thing happens if we prevent one part of the ecosystem from getting the organic molecules (food) that it needs to stay alive.

So, basically, food is organic molecules that are burned inside the body. Most of the energy is then used to do the work of staying alive. All of the functions of staying alive are directed by the genes

Notice, this has nothing to do with burning trees or burning gasoline, and this is one of the very important things the media do not want to tell you about. We are talking about using organic molecules to stay alive, not to drive cars. Burning the organic molecules inside our cells and breathing out the carbon dioxide and urinating the water. Not putting them in a big pile and destroying them. Either way, the result is carbon dioxide and water into the atmosphere, and the energy is gone away as heat.

Global warming.

When the ecosystem is in balance, then the carbon dioxide and water would be breathed in by the plants and used to make more organic molecules, under the direction of the plant genes, so all the related cycles of life could be repeated, over and over again, directed by all the genomes of all the organisms.

Similarly, all the other kinds of atoms and molecules that we need to be alive are recycled by the ecosystem. We don’t need to describe every different kind of cycle, because that information is available on the internet. The important point is that all the animals and plants and other organisms are involved in this kind of recycling. Different kinds of organisms have different tasks in the various cycles. They all work together to keep the cycles of materials balanced so that nobody ends up poisoned and nobody ends up deficient in some kind of atom or molecule that is needed for life to stay alive. The energy to do all this work comes from the sun and is not recycled. (Contrary to what you may have heard in the media.) It is changed into heat. The genetic information that directs all these millions of processes and keeps them in balance is not recycled. It is carried forward by sexual and asexual reproduction from one generation to another, changing a bit over time in response to changes in the conditions of the whole of life (we will describe this next post). Materials recycle; energy flows through and is lost; information, if lost, is forever gone.

This sort of thing does not happen on the moon. It does not happen on Mars. It does not happen on the sun. Because none of those places are alive. It will not happen on the earth if we throw it so far beyond the tipping point that it can no longer recover its balance.

Summing Up

Evolution happens. Not only it happens, but it is one of the most powerful and fundamental forces in all of living nature, along with the laws of thermodynamics, gravity, cause and effect.

In chapter one, we said the entire ecosystem requires energy to do the work of staying alive. We said the laws of thermodynamics describe how energy can or can not flow through the ecosystem. Survival of any living thing is a constant push against entropy, and entropy is a natural law of the whole universe, living and not living, that describes the natural tendency of anything to become un-complex — to fall apart, like a rusty old car in your back yard, compared with the shiny old Model T that you have kept in good repair.

We have also said that life is one of the most complex things that we know about in the universe. It requires energy to keep it that way and nobody is pottering around keeping it in good repair. Life stays alive because of the way the ecosystem works as a whole to keep itself going in spite of the natural laws of the universe. It does this, as we have said a large number of times, fundamentally by three uber-processes that we have discussed in our three chapters.

Chapter One – The flow of energy through the ecosystem, utilizing every bit of organic energy between the time it is created by the plants using sunlight as energy source, until it is lost forever in the form of heat. Every corner of the ecosystem, if it is to continuing doing its function of helping to keep us all alive, must have energy. It is one of the defining characteristics of life that it can keep itself in good repair. This is accomplished by the flow of organic energy from its creation in the plants through all the levels of living organization, the herbivores, carnivores and the organisms that live on dead and decaying matter that still contains organic molecules.

Chapter Two – The recycling of materials is the process that is easiest for us to understand, and yet the apparent simplicity is deceptive, because this recycling, again, relies upon all the interconnected levels of organization of the ecosystem so that, for example, carbon is made available to all of the levels of life from the time the plants use it to make organic molecules until the breakdown of the organic molecules returns it to the atmosphere.

The biggest difference between the materials and the energy is that materials are atoms or molecules of matter that have mass and occupy space. So the maerials just get pushed around on earth from one place to another.  Whatever energy is — it does not stick around to be used again. With respect to the ecosystem it is used primarily as organic energy that is created by plants using light energy from the sun. As every living thing (almost) uses the organic energy, the organic energy changes to heat energy and can never again be used to maintain the processes of life. Heat energy is also useful, but it does not run our generators, so to speak. So materials and energy flow through the ecosystem along the pathways of the levels of organization. The difference is that materials can be recycled but energy can not.

Chapter Three – The flow of information causes all the above things to happen as they do — that is genetics, from the DNA to the gene to the chromosome to the genome of an individual organism to the gene pool of the speces to the evolution of that species to the ability of the whole ecosystem to respond to conditions inside and outside of itself.

Life can be defined as the ability to respond to the environment, from the ability of a cell to find a safe place to live to the ability of your gut to digest organic molecules to the ability of a bird to build a nest to global warming. And beyond that to integration of the entire living earth that we will discuss in the next few posts.

Life is the innate, internal ability to respond to the environment rather than just sit there and be destroyed by it. The flow of information sustains life because it senses the environment and cues the living response. The hand on the hot stove is a reasonable example of this process, but very limiting as a concept because we need the whole of the ecosystem information system to stay alive — in addition to our own nervous system.

Why do cells and organisms require oxygen to stay alive? Because oxygen is necessary for the flow of energy. It is required for our cells to capture the energy from organic molecules, through the process of cellular respiration. Oxygen is provided to us by the ecosystem.

Why does the ecosystem require the recycling of materials to stay alive? So that the plants can use the materials, along with energy from the sun, to make more organic molecules, through the process of photosynthesis.

Why does the ecosystem require the deaths of individual organisms, so that it can give life to more individuals? Because the deaths of individual organisms are necessary for the flow of information through the ecosystem to continue, and the flow of information IS the innate, internal ability of the ecosystem to respond to the environment. That is, the flow of information is the most basic essence of life itself.

Those three most basic of all life concepts – the movement of energy, materials and information over time — will also be the basis for our summing up in the next few posts.

Genetics

The genetic code directs our biological functions — yours and mine and Bitsy (the dog) and Buttermilk Pie (the cat). Every new cell of an organism receives a copy of its own code of life, and then it uses the code to direct the proteins that do all the work of the cells, as we have described, by specifying the functional shape of each protein and producing them when and where they are needed in our bodies. Just for one example, this process makes available all the proteins required to do cellular respiration and so provides the energy that the cell needs to do all these tasks.

The more you think about all the tasks a cell and a body must do to stay alive, the more you recognize cycles inside cycles connected with other cycles. This is why life only comes from other life. When any one of these cycles is broken it not only stops its own task, but also all the other tasks that rely upon it for their functions. For example, the processes of mitosis, meiosis, DNA replication, cell division, all require organic energy that is made available by the process of cellular respiration, and cellular respiration would be impossible without all mitosis, meiosis, etc.

And the purpose of this one individual life seems to be meiosis and the fertilization of an egg by a sperm, a zygote, that will require proteins and energy to grow into an adult to repeat the cycle. These cycles more or less describe the flow of energy through the individual organisms. Even more elegant is the way in which they also participate in the flow of information through the entire living ecosystem.

Because of the processes of meiosis and cellular respiration, each new zygote is unique. It is correct for its species. For example, the new mouse cell contains 20 different kinds of chromosomes, two of each kind, two complete sets of chromosomes. Each kind of chromosome (numbered 1 through 20) contains the correct kinds of genes. For example there is a gene named tyrosinase in about the same position on every chromosome number one of the mouse. So every mouse has two tyrosinase genes. One came from the mother on chromosome number one and the other from the father on his chromosome number one.

However, the new zygote has a different genetic code than either the mother or the father, first because the chromosomes were assorted during the first division cycle of meiosis, and second because all of the genes (though they are of the same kind) are not identical to each other. The tyrosinase gene, for example, is responsible for making pigment in the pigment cells of mammals. It can be normal or it can be abnormal. If it is normal it does its function correctly; otherwise not. If the zygote gets two abnormal tyrosinase genes (one from each parent) then it will not have any normal gene to do the job of making pigment in the pigment cells. Of course, a zygote is not a baby. It is only one cell. However, that cell will make copies of itself until over time there are millions of cells until eventually some of the new cells will become pigment cells.

The genetic code is programmed to make tyrosinase in pigment cells. If the pigment cell is not able to make tyrosinase, then the new mammal will be an albino. If it is able to make tyrosinase, then it will have normal pigmentation. This is an example of just one kind of gene that is found in one location on one kind of chromosome. Similar relationships are possible for any kind of gene on any of the chromosomes. The function of meiosis is to reassort the genes. The function of fertilization is to make new combinations. Every individual zygote is therefore unique. Through all of time, every new generation of every sexually reproducing species consists of individual organisms that are not identical to each other. Every different phenotype is therefore also unique.

The phenotype is the physical nature of the body that results when a gene does its function. For example, the genotype of a normal tyrosinase gene could be referred to as Tyr+. The genotype of an abnormal tyrosinase gene could be referred to as Tyr – . Of course we already know that organisms have two of each kind of gene, so if a person, for example, has two normal tyrosinase genes, then we could write the person’s genotype as Tyr +/Tyr +. That person would make pigment in her pigment cells.

The function of the tyrosinase gene is to make the tyrosinase protein that causes the pigment cell to have pigment. That is, a pigmented phenotype. So the person has a pigmented phenotype.

If we want to refer to all the genes in one person, we use the term genome. If we want to refer to the entire phenotype of a person we could use the term phenome. Most people do not use this term, but I need it for the remaining part of our discussion because the phenomes of organisms, the variability of the phenomes, basically are the source of information flow for the entire ecosystem. They are the code of life of the ecosystem, as we will discuss later. Meantime, this discussion has become sufficiently complicated for today.

To sum up, living things can respond over time to conditions inside their bodies and outside their bodies. If they can not respond to conditions they do not stay alive. It’s not possible to respond to anything unless there is information flow (communication of some sort) between the conditions (cold temperature for example) and the response (putting on a coat). This is even more true of the automatic responses, for example, digesting your food. The ecosystem, to stay alive, also requires information flow. Information flow in individual organisms is a result of the genotypes of their cells. Information flow in the whole ecosystem is the result of the many different ways in which organisms interact with each other at the level of the phenome.

And that is the end of the story of information flow within organisms (genetics) and the beginning of the story of information flow across all the levels of organization of the ecosystem (evolution). Whew!

And don’t forget that every bit of this story requires organic energy or it does not happen.

Meiosis

The important reason to know about meiosis is to understand why/how every individual organism is different if reproduction is sexual, and that this difference constitutes the flow of genetic information within the ecosystem.

We start with Mitosis for comparison:

Mitosis is the process of cell division that results in identical daughter cells (clones). The daughter cells are identical because:

1. First each chromosome in the cell makes an exact copy of itself by the process of DNA Replication but the two identical copies remain connected, as often diagramed so:

The chromosomes (diagrammed unrealistically on the left) are unwound, incredibly long, and invisible to the microscope while they are doing their functions, but after they finish copying themselves they wind up tight and get ready for the cell to divide.  At this point they become so thick that they are visible microscopically, and in order to identify them, people who like to look at chromosomes have agreed on a numbering system.  For this example, let’s pretend the green chromosome is number one chromosome, still attached to its exact copy, all wound up inside a cell and ready to line up on the central plane of division.  The purple chromosome we will name number four.  This is a mouse, with 20
different kinds of chromosomes, but we don’t want to show all 20
in our example so we are showing only one chromosome one and one chromosome four.  Maybe it looks to you like two of each chromosome, because the exact copy has already been made.  But until the exact copies become separated, we say it is one chromosome of each kind.

2.   Then the nucleus breaks down;

3.  Then the chromosomes all line up individually along the plane of division.  This is where the cell will pinch itself apart to make two cells;

4.  While the chromosomes are lining up, microtubules come from each end of the cell, so that, for example, the chromosome number 4 has microtubules attached to each side of the chromosome and to their source at each end of the cell.  And also the chromosome number one.

And then the microtubules simply pull the chromosome’s exact copies apart from each other, and the cell divides, on the plane of division, which is now between chromosome one and its exact copy — and between chromosome four and its exact copy, and all the other chromosomes. So the two cells each get an exact copy of each chromosome because of the way the chromosomes duplicate, then line up separately and are pulled, one duplicate to each end, by the microtubules.

HOWEVER.  It’s not quite that simple.  (You say you are not surprised?)  I may have omitted to say that chromosomes of most higher organisms come in pairs.  So in fact this mouse has 20 different kinds of chromosomes (1, 2, 3, 4, 5, 6, 7 etc.) in each of its body cells, and it has two of each kind.  Two of chromosome number one and two of chromosome number two, and so on.  One chromosome number one came from the father in the process of fertilization.  The other chromosome number one came from the mother in the same process of fertilization.  The two are not identical, as I will explain in the next post, but they do have the same genes in the same sequence encoded along their lengths.  So all the number one chromosomes have the same genes, all the number two chromosomes have the same genes, but they are different from number one, etc.  Some kinds of plants have even more copies, but we will stick with the basic principles of how these all get sorted out in meiosis.

So in our mouse example, every body cell has 20 different kinds of chromosomes that are numbered sequentially (according to their size), and every body cell has two of each kind (total 44 chromosomes). The other way to say the same thing is:  Every body cell has two complete sets of chromosomes (20 in each set, one of each kind), one that came from the father and one that came from the mother.  The condition of having two sets of chromosomes is known as diploid (di = two).   The chromosomes that come from the father are homologous to those that come from the mother, but they are not identical.  Homologous is defined below.  Before that we need to take a closer look at sexual reproduction, because it is responsible for the variability among individual organisms, and the variability is responsible for the flow of information in the whole earth ecosystem.

The body cells all have two complete sets of chromosomes, but the sex cells have only one set.  The sperm carries one complete set of chromosomes, and so does the egg.  That means, in this example, the sperm has one of chromosome number one (it is haploid) and the egg also has one of chromosome number one (also haploid) so that when the egg and sperm fuse together the result is a normal fertilized egg (a zygote) that is diploid and can give rise to body normal body cells by the process of mitosis.  Haploid means one/half the number of sets of chromosomes that are normal for that species.

Fertilization is the process of fusion of gametes.  A gamete in mice is either an egg (from the mother) or a sperm (from the father). More formally, a gamete is a haploid sex cell, and meiosis is the process of cell division that results in haploid gametes.  Every gamete is haploid  so that every new fertilized egg can be normal.

So in a mouse, each of the body cells is diploid, meaning it has two sets of chromosomes.  The sex cells, eggs or sperms, are haploid, so they each have one complete set of chromosomes.

It is the forever cycle of life; it is the foundational reality that permits evolution and the flow of information within the ecosystem.  But before we get to that dramatic finale, the next question is:

How does that clever cell manage to sort out all those 20 pairs of chromosomes that are copied in every body cell of the mouse — so that each gamete gets one complete set — no more and no less?  And isn’t that what we started out to talk about?

There are two tricks to meiotic cell division that make the results different from mitotic cell division:

1.  The starter cell goes through two different sequential sorts of division during meiotic cell division, instead of one as in mitotic cell division;

2.  The chromosomes line up along the plane of division in pairs, rather than individually, during the first meiotic cell division.

So here is the diagram, beginning with a normal mouse cell that has two sets of chromosomes.  We are showing only chromosomes one (the green one) and chromosomes four (the purple one).  All the other 20 pairs of chromosomes are similarly sorting themselves out at the same time.

Sexual Reproduction

The ability to respond to stimuli is one of the characteristics of life. The amoeba in a pond will move toward a food source; you remove your hand from the hot stove; the snake curls up in a sunny spot on a cold day; the living ecosystem evolves. Living things interact with their environments. That is one way that they maintain the balance of life — temperature, energy, information. Rocks and minerals do not do these things.

It’s perfectly obvious that the hot stove example is interacting with the environment; it’s not so easy to recognize that information is necessary for that interaction until we remember that the proteins are responsible for building our nervous system, and the proteins get their instructions from our genes, as we have just finished discussing. So the genetic information of the individual organism is responsible for how it is able to interact with its environment. The genes carry the information, and the primary function of asexual reproduction is to pass this on, when the cell divides, to both new cells. The primary function of asexual reproduction is to maintain these life functions of individual organisms; the primary function of sexual reproduction is the survival of the species and of the ecosystem.

Asexual reproduction is the process of reproduction by mitosis followed by cell division. The result of asexual reproduction is genetically identical daughter cells (that is cloning). In multicellular organisms, asexual reproduction is the primary mode of information flow within the individual. Each genetically identical daughter cell of the whole organism carries the same genetic code, making it available as needed to direct the processes of life.

Sexual reproduction is the process of meiosis followed by fertilization. It is very unlikely that sex was created to sell cars — or for your personal pleasure. Much more probably, that pleasure was created in order to maintain sexual reproduction, as a necessary element of the ecosystem’s response to stress. Sexual reproduction is the primary mode of information flow through time in the ecosystem. The implications of this concept will occupy us for another week or two. The output of sexual reproduction is genetically variable zygotes that result from the fusion of an egg and a sperm (or two cells that are similar to egg and sperm).

In the next post we will describe meiosis and fertilization, briefly because the information is easily available. Then we will discuss the essence of evolution — how it happens, based on sexual reproduction, and how it functions to maintain the balance that is necessary for the survival of the ecosystem.