It is mutagenesis that causes beneficial mutations to appear, and it is selection that spreads beneficial mutations through the population. The environment is causing the selection.
You would be wrong. While most DNA sequence changes are neutral that doesn’t do away with positive selection for beneficial mutations. Neutral drift and positive selection are not mutually exclusive.
Rapid changes are more likely to kill off organisms than cause this effect aren’t they?
Wouldn’t a slow change be required to give time to adapt?
All of this under the assumption that some part of the population already has an adaptation that will ensure survival.
Edit: and od course, the solution could be to just walk away… I.e migration.
Very confused. Evolution is mostly neutral, but that’s because the bulk of your genome is junk, unaffected by selection. But if you’re talking about adaptive evolution, it isn’t true that evolution is mostly drift (though a lot of it still is). Selection actually is quite powerful; it can fix a mutation much, much faster than drift can. Now, fixation depletes variation. If the environment is changing faster than variation can be recharged by mutation, eventually the rate of adaptation must slow as existing variation is depleted and not recharged. The likely result there would be extinction, as change outpaces the ability to adapt. But if the rate of environmental change is not enough to outpace the recharging of variation by mutation, then the rate of environmental change does indeed determine the rate of adaptive evolution, long-term.
If mutations are lethal then they don’t spread through the population. Death is a strong inhibitor of reproduction.
No.
Extinction is certainly an option. Given that there is still life on the Earth it means that some lineages have survived.
Isn’t it more often fixed due to drift than selection?
How many mutations are strong enough to be selected for by the environment?
A rapid change would have the most like result that the organism is not prepared and dies off.
Why should there be a big enough change to be selected for? If the change in environment is drastic, it’s more likely that phenotype that could be a solution has been wiped off by negative selection before the change.
Except that the pattern of rapid phenotypic change with change in environment requires that selection is dominant. The result should be extinction in the vast majority of cases. Hence rapid environmental changes should result in loss in the overall gene pool and detrimental to evolution in the long term.
That’s the way I see it.
99.9% of all species which ever lived are extinct.
Relatively rapid. Thant means over tens of thousands to hundreds of thousands of years instead of millions. It doesn’t cover catastrophic events like Chicxulub.
Again, drift and positive selection are not mutually exclusive. Both effects can be occurring in parallel.
Depends on the environment and the mutation.
That’s a bare assertion.
If the mutation can happen once it can happen again. Every generation is born with new mutations. Mutations can cause very little change or cause lots of change.
That’s another bare assertion. You need to back this up with evidence.
If only 10% of the genome is functional then you don’t need selection in a majority of the genome. You only need selection in 10% of the genome.
What exactly do you mean by recharging of variation.
Are you suggesting that there is an optimal “rate of environmental change” that leads to maximum adaptive evolution? Anyone ever measure this?
If a mutation rate is too high then it can be deleterious.
If as you say, 99.9 percentage of all species are extinct. Then it means that in the vast majority of cases, the result is extinction inspite of the rate of environmental change.
I.e the larger picture is one of loss of genetic variation.
This doesn’t justify the claim that a more rapid rate of change in environment causes an increase in adaptive evolution. The big picture shows a negative overall.
Deleterious doesn’t mean “adaptive evolution” does it?
Deleterious means it can lower overall fitness. As the mutation rate increases you have to have more and more offspring for selection to remove the harmful mutations. It’s a concept called mutational load.
Firstly, I use bold, and uppercase and such not to represent shouting (usually) … but to modulate my tone in the absence of the more nuanced communication of speaking.
Secondly, sometimes lyrical or highly figurative analogies really communicate the necessary message. And your unwillingness to “go with the flow” with some metaphors seems to be more oppositionalism than anything else.
Otherwise, sometimes when people show colored exhibits, that are lost on the colorblind, the color-blind person will get a little more cooperation if they admit they are color-blind… not just fussy.
I understood that… what I didn’t get is what it has to do with what @John_Harshman is saying.
He is talking about the rate of environmental change and “recharging variation”…
Do you know how variation gets recharged?
@John_Harshman is covering a “real” thing.
Who can say how many species (simple or complex) there have been on Earth that attained very high levels of accuracy in replicating their genetic material… only to be wiped out when the climate of Earth or of a region drastically changed?
Perfect DNA replication can be the mortal problem for any life, when looked at from the perspective of a whole population, rather than the perspective of a single individual.
Yes. Variation gets recharged by mutations that occur in every individual in every generation. For example, each human is born with 50 to 100 mutations. In a population of just 1 million humans that is 100 million new mutations in just one generation.
Fixation of an allele reduces variation at that site and fixation of alleles at multiple loci reduces variation in the genome. Mutation increases — recharges —variation.
Yes, that’s probably true.
Possibly. Are you familiar with the experiment in which bacteria are introduced to a plate with a gradient of antibiotic concentration? It’s an internet meme.
It doesn’t help. It just makes it look as if you’re shouting. To modulate your tone in written communication, you need to adjust the words, not the font.
And sometimes they don’t. In the case at hand, your analogy communicates nothing. Perhaps you could explain the mapping. How are mutations (which I assume, in the absence of clear statement, you’re talking about) analogous to my hand?
That’s known as “blaming the victim”.
Except that there is no guarantee any of this variation is useful. At any point of time doesn’t the no: useful variations in the total no: of available mutations have to be random?
Are you assuming that a fixed percentage of mutations will provide useful variations according to whatever environmental change is going on? (If the ratio of useful variations to total no: of mutations is random, then rate of change should be random).
I don’t see how anyone can predict this… or how this can be anything other than a random value.
No, but I will read through it if you can share the details.
I would agree with you … except you have accused me of being UNWILLING to explain something to you … after five or six attempts by me where your response is simply “I don’t get it”.
Maybe it’s time to find another hobby?