Difficulty understanding evolution

[Bystander]

For the admin, I know this is becoming unscientific, and hope we can get back on topic asap

Hear. Hear.

 

[Adamchiv]

this is a physics community granted on a biology sub- forum. Have you considered joining a biology forum with a dedicated evolutionary biologist community.

No offense to the physicists here.

No because the answers here have been very helpful

 

[Drakkith]

Agouti, sable, black brindle cats - where have you seen that in domestic cats??

All our wild cats here are from domestic stock.

I'm pretty sure I found all of those on domestic cats in google images just now. But I don't know cat coat colors that well, so I may be mistaken (though I did look them up to try to make sure).

Can anyone tell me at roughly what point all the main organs became inherant, I know its gradual, but for example did our ancestors (i.e earliest life forms) live a long time without a liver, or kidney etc

Basic organs were part of the earliest multicellular life forms. As an example, take a look at a jellyfish. They've been around for somewhere between 500 and 700 million years and they have multiple rudimentary organs, including a nervous system, digestive system, and more. These organs aren't nearly as complex as ours, but they were probably among the most advanced organs at one point in time.

Organs that more closely resemble ours can be found in fish and evolved somewhere around 350-400 million years ago. The main organs are probably a hard requirement for complex life to develop. Without ways to efficiently process food, get rid of wastes, and seal the organism's internal systems from the outside world, complex life cannot develop.

 

[Adamchiv]

Without ways to efficiently process food, get rid of wastes, and seal the organism's internal systems from the outside world, complex life cannot develop.[/QUOTE]

Youve just sent me on another tangent why did we ever (again I say we as the whole spectrum of evolved life) start to need oxygen and require food? Does this stem back to the fact that bacteria requires some sort of energy nurishment? And does bacteria need oxygen? Does it all stem back to bacteria? Or a little further down the line? (Sorry) your previous answer was very helpful

 

[Bystander]

why did we ever (again I say we as the whole spectrum of evolved life) start to need oxygen and require food?

Energy. Are there other energetic chemistries than coupled oxidations and reductions? Yes. Are they common? No.

 

[BillTre]

Oxygen allows biochemical processes to extract more energy from their food molecules.

Life is pretty energy intensive (compared to a rock).
In some cases each proton moved across a membrane is pumped with cellular energy.
The addition of each amino acid to a protein chain uses energy.

 

[Drakkith]

Youve just sent me on another tangent why did we ever (again I say we as the whole spectrum of evolved life) start to need oxygen and require food? Does this stem back to the fact that bacteria requires some sort of energy nurishment? And does bacteria need oxygen? Does it all stem back to bacteria? Or a little further down the line? (Sorry) your previous answer was very helpful

All living things expend energy to stay alive, even bacteria and other unicellular organisms. The source of this energy is whatever the organism uses as food. Oxygen or other chemicals are required to complete the reaction, which generates other molecules like adenosine triphosphate (ATP) that serve as the immediate energy source for each cell. I believe ATP is used in all living creatures, so it likely evolved LOOOONG ago.

 

[rootone]

The first lifeforms on Earth did not need Oxygen, at least not as a free gas.
When some later life evolved photosynthesis using light as an energy source, they released free Oxygen as waste.
Only then did Oxygen became a major component of the atmosphere
This turned out to be deadly rather than nourishing for most of the previously existing organisms.
https://en.wikipedia.org/wiki/Great_Oxygenation_Event

These first photosynthesizing microbes are probably the common ancestor of all plant life on Earth today.

 

[sarrabeth]

It seems as though you've picked up too much information on evolution, without a proper framework to put it on. That often happens when you're teaching yourself through books or videos. For a basic understanding of evolution, I recommend Nova's Judgment Day. It will also tell you how a whale's nose ended up on the top of it's head, and ours didn't.
Mutations are random, but evolution moves in whatever direction the species needs to go in order to survive (hopefully). The variety of genes that exist in a population are what ensures survival. There's a moth, in England, that hides on the bark of a tree. The moth is a greyish white, with black speckles, as is the bark of this tree. At one time, 3 out of 4 moths were this color, with the odd one more of a black. The black ones were easily seen against the white bark, and few survived. In the 19th century, England was burning huge amounts of coal, and the bark of the trees began to turn black. Before long, 3 out of 4 moths were black, rather than white. When cleaner fuels were used, the trees began to look white again, and the moths went back to their original color. This is not evolution, it is an example of how natural selection works on the existing variations in the gene pool. Natural selection is whatever predator is eating the moths that don't blend in. If the black ones are eaten, than the white ones survive, and vice versa.

 

[Drakkith]

When cleaner fuels were used, the trees began to look white again, and the moths went back to their original color. This is not evolution, it is an example of how natural selection works on the existing variations in the gene pool.

No, that's evolution also. Evolution is simply the change in heritable traits in a population over time, and it includes the causes of that change.

 

[sarrabeth]

No, that's evolution also. Evolution is simply the change in heritable traits in a population over time, and it includes the causes of that change.

Thank you for responding.
It seems to me that the heritable traits have not changed, since both colors were and are present. If the situation had not changed, and continued to favor the darker colored moths, maybe the lighter variation may have disappeared, but I doubt it. The very fact that a population has a lot of variations is a way of ensuring that a portion of the group might survive a sudden change in environment. If the genome of a group is too similar, all it takes is a new disease or climate change to pretty much wipe it out. Or humans moving into the area.

 

[Drakkith]

It seems to me that the heritable traits have not changed, since both colors were and are present.

The traits themselves have not been altered, as this isn't an example of a mutation, but natural selection acted upon the population and changed the proportion of white vs dark colored moths in response to the changing environment. This is a clear-cut example of evolution. Note that natural selection is a mechanism by which evolution occurs, and it is only one of several mechanisms. Other mechanisms include genetic drift and genetic hitchhiking.

See here: https://en.wikipedia.org/wiki/Peppered_moth_evolution

The very fact that a population has a lot of variations is a way of ensuring that a portion of the group might survive a sudden change in environment. If the genome of a group is too similar, all it takes is a new disease or climate change to pretty much wipe it out.

Indeed. Variation is important to ensuring a population is resistant to sudden changes in their environment or exposure to diseases.

 

[lavinia]

I sent your question to a biologist friend. Here is the first part of his response.

"A lot of issues here. Let’s start with the lumps on the arms etc. First, one has to distinguish the evolution of complex structures from single gene mutations that occur in a single generation. The lumps on the arm are presumably an example of the latter. Whether any mutation is truly “neutral” meaning that it confers no selective advantage or disadvantage is still, I believe, a matter of debate. However, if mutation does not confer a selective advantage, it is likely to be diluted into the gene pool to such an extent that it’s reappearance seems more like a random event. There are mutations that fit this description - white forelock, sixth finger etc. Note that neutral or even deleterious mutations can gain in frequency in a subpopulation where inbreeding occurs and dilution is not possible. So, for example, the hemophilia mutation is relatively common on Pitcairn island as well as in the British royal bloodline. The bottom line here is that we don’t have lumps on our arms because the lumps confer no selective advantage and we are not inbred.

More on the complex structures in a subsequent note when more time is available. "

 

[Adamchiv]

I sent your question to a biologist friend. Here is the first part of his response.

"A lot of issues here. Let’s start with the lumps on the arms etc. First, one has to distinguish the evolution of complex structures from single gene mutations that occur in a single generation. The lumps on the arm are presumably an example of the latter. Whether any mutation is truly “neutral” meaning that it confers no selective advantage or disadvantage is still, I believe, a matter of debate. However, if mutation does not confer a selective advantage, it is likely to be diluted into the gene pool to such an extent that it’s reappearance seems more like a random event. There are mutations that fit this description - white forelock, sixth finger etc. Note that neutral or even deleterious mutations can gain in frequency in a subpopulation where inbreeding occurs and dilution is not possible. So, for example, the hemophilia mutation is relatively common on Pitcairn island as well as in the British royal bloodline. The bottom line here is that we don’t have lumps on our arms because the lumps confer no selective advantage and we are not inbred.

More on the complex structures in a subsequent note when more time is available. "

Thanks very much to you and your biologist friend! I will read up on the hemophilia mutation

 

[lavinia]

Here is the second installment of my friend's response.

"
Where complex structures like a nose and mouth are concerned, it must be appreciated that they did not arise as a single mutational event, but developed as stepwise elaborations of primordial structures. In multicellular invertebrates that are either sessile or that do not benefit from movement in a straight line (e.g. sea cucumber, slime mold) there is no selective advantage to development of a midline around which structures are placed symmetrically. However, in multicellular vertebrates for whom movement is a straight line is advantageous for targeting food sources, escaping predators, etc., development around a midline has a selective advantage. Symmetrical development around this midline helps maintain this selective advantage (fins on either side of the fish vertebral column, legs on either side of the early amphibians), and this arrangement thus dominates the anatomy of multicellular vertebrates. The nose is not a single structure but a complex one that connects both to the respiratory system and the brain. It is situated around the midline, with parts placed symmetrically on either side of the midline. The same holds for the mouth, which is just a part of the digestive system. While it’s theoretically possible to find a mouth at, say, the top of the forehead in the midline, evolution of the digestive system occurred in a coordinated fashion with the central nervous system. For the mouth to be at the very top of the head, the esophagus would then have to travel through the brain without disrupting brain function, which depends on communication between neurons on either side of the midline, and which was also evolving with the digestive system. Given the arrangement of these structures in primordial species, it is highly unlikely that any single genetic event could effect such a dramatic rearrangement. Moreover, were that to happen, it is prohibitively unlikely that the new arrangement would confer a selective advantage.

The notion that complex structures arise as stepwise changes in corresponding systems found in ancestral species also holds for networks like the circulatory system. Circulation arose to allow cells deep inside solid organs receive needed oxygen, and once the system developed, it is not feasible to imagine new organ systems arising that would obtain oxygen by some other method. Note that in insects, which are invertebrates whose evolutionary tree goes back to ancestral invertebrates that did not have a circulatory system, such a system does not exist, and cells receive oxygen through conduits that connect from the surface of the body. The insect system is not too different from that of the invertebrate sea cucumber. It’s not surprising that the insect system is not well adapted to vertebrate organisms with very large organs that may be billions of cells thick. So, the insect system is built on the tubule structure also found in the sea cucumber, while the arterial/venous system is descended from the oxygenation system of early vertebrates.

The underlying motive force for skepticism about complex structures evolving rather that being designed by an intelligence stems, in my view, from a lack of appreciation of the amount of time evolution has been taking place. Most people cannot really get a handle on a time frame of 40 million centuries, which is a reasonable estimate of the time since life first appeared. A lot of genetic experiments that failed can take place over that expanse of time. "

 

[Adamchiv]

Here is the second installment of my friend's response.

"
Where complex structures like a nose and mouth are concerned, it must be appreciated that they did not arise as a single mutational event, but developed as stepwise elaborations of primordial structures. In multicellular invertebrates that are either sessile or that do not benefit from movement in a straight line (e.g. sea cucumber, slime mold) there is no selective advantage to development of a midline around which structures are placed symmetrically. However, in multicellular vertebrates for whom movement is a straight line is advantageous for targeting food sources, escaping predators, etc., development around a midline has a selective advantage. Symmetrical development around this midline helps maintain this selective advantage (fins on either side of the fish vertebral column, legs on either side of the early amphibians), and this arrangement thus dominates the anatomy of multicellular vertebrates. The nose is not a single structure but a complex one that connects both to the respiratory system and the brain. It is situated around the midline, with parts placed symmetrically on either side of the midline. The same holds for the mouth, which is just a part of the digestive system. While it’s theoretically possible to find a mouth at, say, the top of the forehead in the midline, evolution of the digestive system occurred in a coordinated fashion with the central nervous system. For the mouth to be at the very top of the head, the esophagus would then have to travel through the brain without disrupting brain function, which depends on communication between neurons on either side of the midline, and which was also evolving with the digestive system. Given the arrangement of these structures in primordial species, it is highly unlikely that any single genetic event could effect such a dramatic rearrangement. Moreover, were that to happen, it is prohibitively unlikely that the new arrangement would confer a selective advantage.

The notion that complex structures arise as stepwise changes in corresponding systems found in ancestral species also holds for networks like the circulatory system. Circulation arose to allow cells deep inside solid organs receive needed oxygen, and once the system developed, it is not feasible to imagine new organ systems arising that would obtain oxygen by some other method. Note that in insects, which are invertebrates whose evolutionary tree goes back to ancestral invertebrates that did not have a circulatory system, such a system does not exist, and cells receive oxygen through conduits that connect from the surface of the body. The insect system is not too different from that of the invertebrate sea cucumber. It’s not surprising that the insect system is not well adapted to vertebrate organisms with very large organs that may be billions of cells thick. So, the insect system is built on the tubule structure also found in the sea cucumber, while the arterial/venous system is descended from the oxygenation system of early vertebrates.

The underlying motive force for skepticism about complex structures evolving rather that being designed by an intelligence stems, in my view, from a lack of appreciation of the amount of time evolution has been taking place. Most people cannot really get a handle on a time frame of 40 million centuries, which is a reasonable estimate of the time since life first appeared. A lot of genetic experiments that failed can take place over that expanse of time. "

This is an amazing answer, simple enough for me to understand yet answers my biggest misunderstandings! Superb work

 

[gabi123]

Essentially, think of evolution as a bell curve. There is a certain path for every human, but a minority stray away. Mutations, as you described, happen not in terms of evolutionary theory. They could be from disease, or elsewhat.

 

[Adamchiv]

Essentially, think of evolution as a bell curve. There is a certain path for every human, but a minority stray away. Mutations, as you described, happen not in terms of evolutionary theory. They could be from disease, or elsewhat.

I thought mutations were genetic defects that can be passed down through generations? Surely there were a lot of mutations early on that effected small groups and tend to have little effect in large groups later on when the species gene pool is strong

 

[Pythagorean]

Mutations are something that happens - it's a neutral word. Whether they are a "defect" or an "adaptation" depends on how the mutation affects organism function and how you define functionality in the first place.

 

[BillTre]

In addition, new mutations can reverse the effect of other mutations, either directly or indirectly.
The genome can be considered a string of characters (of A, T, C, or G).
Changes can be made.
These can be transmitted to offspring and compose their genome.
The breeding population's genomes are the gene pool selection acts upon.
The character string can be mutated again and might (with a low probability) exactly change a mutation back to what it was before. This would be a back mutation.
In addition, a mutation at another place in the genome might make a change affecting some process that reverses the effect of the first mutation (through perhaps some physiological process) that will make the phenotype (what the organism looks like) like it was before the first mutation was acquired. This is sometimes called a suppressor. The original mutation would still be there, but its effect would be "muted".

 

[Adamchiv]

I didnt mean to put defect, I shouldve put change instead. I was just trying to recognise what causes mutations, I thought that it was mostly to do with changes in offspring rather than desease etc

 

[rootone]

There a number of possible reasons why a mutation can occur.
One is that the DNA replication chemistry, while it's wondrous and has 'error checking', it isn't 100% perfect.
Mistakes can happen in such a highly complex set of chemistry.
Mutation may also arise due to the interference of factors external to the replicating process itself.
Ionizing radiation even at background levels is a well known example,
https://bioethicsarchive.georgetown.edu/achre/final/intro_9_5.html

 

[BillTre]

Mutations can also come in a variety of changes:
1) change on a single base (A, T, C, G) to a different base
2) addition of one or more base to a particular location in a sequence (insertion)
3) deletion of one or more bases to a particular sequence (deletion)
4) take and section of sequence and flip it around (inversion)
2, 3, and 4 can result from either chemical treatments, x-rays, gamma-rays, experimental insertions, natural biological inserts (like transposons or viruses), or other stuff(??). These are known as breakpoint mutations because physical breaks have to be formed in the DNA for them to happen.
Juxtaposing different genetic elements can also have effects on gene expression by among other things bringing control elements closer to a coding sequence. Breakpoints can do this.

 

[Chris Miller]

We know evolution doesn't have a conscious mind...

How?
I like De Chardin's view of evolution as "the rise of consciousness."

 

[rootone]

How?

Because there is a perfectly good explanation of evolution (backed up with evidence) that does not require a conscious mind

 

[phinds]

How?
I like De Chardin's view of evolution as "the rise of consciousness."

Evolution may be looked at at the rise of consciousness, but that is NOT the same as saying that evolution has a conscious mind, a concept that is patently ridiculous unless you are talking about a god in which case you are on the wrong forum.

 

[rootone]

Evolution may be looked at at the rise of consciousness ...

Only if taking an anthropocentric point of view regarding humans beings as a goal of evolution.
99%+ of modern lifeforms on Earth have not developed self awareness, yet they continue to exist and evolve.

 

[Chris Miller]

Ray Kurzweil, in "The Age of Spiritual Machines" grants evolution a small IQ. I'm not talking about a god (unless one defines "god" as existence). I'm talking about a universe (existence) that would appear to have some objective beyond mere survival and some small ability (given time) to meet this objective.

 

[phinds]

Only if taking an anthropocentric point of view regarding humans beings as a goal of evolution.
99%+ of modern lifeforms on Earth have not developed self awareness, yet they continue to exist and evolve.

No argument. I did not suggest that it was a good idea to consider it that way, just that one COULD should one choose.

 

[phinds]

Ray Kurzweil, in "The Age of Spiritual Machines" grants evolution a small IQ. I'm not talking about a god (unless one defines "god" as existence). I'm talking about a universe (existence) that would appear to have some objective beyond mere survival and some small ability (given time) to meet this objective.

Positing a universe that has ANY objective IS positing a god, or at best metaphysics. In either case, it is not physics.

 

[Chris Miller]

Positing a universe that has ANY objective IS positing a god.

Are you not part of the universe?

 

[phinds]

Are you not part of the universe?

What does that have to do with anything ?

 

[Chris Miller]

We are tools of evolution. Look how fast computers and AI are evolving. Nothing has changed evolution-wise from the big bang, except the pace.

 

[Ryan_m_b]

We are not the tools of evolution and Ray Kurzweil will say anything, fix any graph and cherry pick any data to support his quasi-religious belief in the singularity. Evolution is a biological process of change in allele frequency in populations over time. Saying that evolution is a tool of the universe to create consciousness within the universe is nothing more than a semantic fallacy of implying the universe acts with intent.

This thread ran its course, there's no discussion of evolution ocuring anymore so thread locked.