Simple (?) Evolution Question
- Thread starter aaronmark
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I am not really certain how to scientifically tell you but it is through adaptation and sometimes gene mutations. As when fish started to walk on land , over many thousands of years they developed a way to do so. The more fish that started walking out of the water the more they attracted other fish like them to propagate their new way of life. :shrug:
It's a good question!
I’m going to pre-empt a lot of replies here. Usually when someone asks this question on an internet science forum there is a stampede of people who will rush to talk about mutation and natural selection. Whilst it is true that these processes produce DNA variation and new allelic combinations, they act on existing DNA. They do not produce new DNA. So where does new material come from on which mutation and natural selection can act?
New material comes from a couple of difference sources. The primary source is the accidental duplication of DNA. Sometimes cells make mistakes when copying their DNA during cell division, and sometimes these mistakes happen during early embryonic development resulting in an organism carrying the mistake in all its cells. There can be duplications of portions of genes, whole gene duplication, partial chromosome duplication, whole chromosome duplication, partial genome duplication, or whole genome duplication. All these events create new DNA on which mutation and natural selection can act.
When whole genes and chromosomes are duplicated they are not functionally constrained and are free to accumulate mutations that, over time, turn them into new genes with new functions. As you can probably imagine, when whole genomes are duplicated there is a tremendous amount of new material that is created. Much of it is lost over time, but the remaining duplicated material is re-shaped into new genes. This has happened in many plant and animal lineages at various times over the course of the evolution of life on this planet.
This duplication in genetic material is demonstrated by the fact that more complex multicellular organisms (eg. humans) have gene families. In other words, “simpler” organisms (such as the extensively-studied fruit fly Drosophila melanogaster and round worm Caenorhabditis elegans) have single copies of genes, whereas those same genes are present in complex organisms as gene families – several related genes with similar overall features but also with differences that impart differing functions that are applied in different cells/tissues at different stages of development.
There are other sources of new genetic material. DNA repair mechanisms sometimes make mistakes that result in insertions of new DNA at the site of repair. Transposable elements have had a large impact in the shaping of plant and animal genomes. They move around the genome and sometimes copy and insert host DNA in the process of moving around between chromosomes.
And a great answer.
For flight, the "flying squirrel" would be a good example of an intermediate step on the way to true flight. It can't really fly, it just has a kind of membrane it can spread that allows it to sort of glide between trees.
Now you can imagine a species like a flying squirrel could have existed way back when. Over time, those with the ability to glide better survived and more and more changes occured until actual flight was achieved.
The biomolecular method that allowed these changes to occur is irrelevent. So long as change is possible, those changes that are most advantageous will come to dominate the gene pool.
Now you can imagine a species like a flying squirrel could have existed way back when. Over time, those with the ability to glide better survived and more and more changes occured until actual flight was achieved.
The biomolecular method that allowed these changes to occur is irrelevent. So long as change is possible, those changes that are most advantageous will come to dominate the gene pool.
Fraggle Rocker
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It's been recently discovered that many "flightless" birds can use their wings to generate negative lift. This gives them better traction when running away from predators. It also allows them to scale steep grades. A chicken can "run" up a vertical slope and even up one that is slanted a bit backwards. No predatory mammals can catch them.
So even tiny wings that were useless for flight became survival advantages because they had other uses that we had not considered, until somebody happened to use a high-speed camera to photograph a frightened chicken.
So even tiny wings that were useless for flight became survival advantages because they had other uses that we had not considered, until somebody happened to use a high-speed camera to photograph a frightened chicken.
Viral infection can insert DNA into genomes.
Bacteria can pick up DNA straight from the environment (pieces of other genomes, etc) as well as from sex, etc.
Symbiosis can, over time and accidents, result in merger or combination of two genomes.
Beings set up to have more than one genome in the cell (various fungi, say) can sometimes incorporate another.
Just ornamenting Hercules post - - -
Bacteria can pick up DNA straight from the environment (pieces of other genomes, etc) as well as from sex, etc.
Symbiosis can, over time and accidents, result in merger or combination of two genomes.
Beings set up to have more than one genome in the cell (various fungi, say) can sometimes incorporate another.
Just ornamenting Hercules post - - -
Yeah, that's true. However, those fruit are seedless, so I'm still left wondering how new genetic material could be passed down? This seems to hold true in humans and animals as well. Extra chromosomes and genomes tend to make organisms sterile and less capable of survival.
Have scientists ever observed an introduction of new genetic material that resulted in a species becoming more fertile and better able to survive? (Excluding natural selection; I'm only interested in new genetic material.)
Have scientists ever observed an introduction of new genetic material that resulted in a species becoming more fertile and better able to survive? (Excluding natural selection; I'm only interested in new genetic material.)
A genome is the entire gene sequence. Alterations in the genome are called mutations. Mutations are mostly not beneficial, but sometimes they are. Experimentation with fruit flys can produce many observable mutations, not all of which are fatal. Some are selected by scientists, and may reflect something that could have happened in nature, that would be selected favorably by the environment in certain conditions.
That's cool. Do you know of any specific cases or studies? I've read several studies (in Nature; with plants and insects) where scientists were able to develop traits that might indeed be favorable (e.g. larger size, longer lifespan) but the inability to reproduce was always increased. I'm just curious if any discovery to the contrary has been made.
There are traces of this having happened in the past in almost every genome studied - the blood clotting genetics in humans, for example.aaron said:
But it might be very rare that such an event would be recognised in a laboratory or controlled setting, even as often as it happened (not often), partly because a favorable modification for a wild setting probably would not be visible without the wild setting, and partly because the kinds of screening necessary to spot it would be expensive and without economic benefit in normal laboratory setups - they want to spot seedlessness, so they don't bother sequencing the watermelons that make more seeds, more viable seed under wild conditions, seeds better adapted to years of dormancy, seeds more resistant to rodent attack, seeds producing smaller fruits more likely to be spread by birds, etc etc etc.
Breeders and engineers usually want mal-adapted plants - from a wild eco point of view. That's what they are looking for, that's what they are likely to find - and finding is expensive.
Ah, but the words I posted have a particular kind of meaning. For example, some organisms don't use sexual reproduction, so in that sense they are "born sterile". But they reproduce or replicate their DNA.
Retardation is specific to humans, or, at least I'm not too sure about any studies of mental ability or equivalent of "Downes Syndrome" in other animals. Death hits the nail on the head though - if an organism dies before it gets "born", or just after (because it ain't equipped) it won't replicate.
Retardation is specific to humans, or, at least I'm not too sure about any studies of mental ability or equivalent of "Downes Syndrome" in other animals. Death hits the nail on the head though - if an organism dies before it gets "born", or just after (because it ain't equipped) it won't replicate.