This query is directed mostly to those involved in genetics, or in genome mapping. When seeds/plants were created, did the creator vary the genes in seeds / plants growing in the temperate regions from those in the tropics? OR, is the genome similar but dominant factors are brought into play? Wonder whether Science has reached the point to unravel this mystery!!
This question needs to be rewritten: "is the genome similar but dorminant factor is brought into play?"
Daniel, Now you got me puzzled and I am unable to follow your line of thinking. Appreciate if you can elaborate the point you have brought up. Thanks.
Well, first of all, dorminant isn't a word - is it supposed to be dominant or dormant? I then tried to understand the sentence substituting either one of those words, and there is something grammatical about it that still doesn't make sense to me.
Daniel, Sorry I was unaware of the spelling error, it should read 'dominant', which is from the root word 'dominate'. I am more inclined to the thinking that the genes controlling the hardiness aspect of an organism remain similar, whether the seed comes from the temperate zone or the tropics. The reason why a particular seedling is adapted to the environment it came from is explained by its selection of those genes that is attuned to its environment to dominate after fertilization. If this position is accurate then modifications required to survive in an environment foreign to its nature would trigger the dominance of another set of genes after fertilization. Then in this case no genetic change has taken place but only a change in the selection criteria. Hope I have not created more confusion by this line of argument.
I'm not sure I understand at all what you are asking. Are we talking about seeds from the same species of tree? Nothing about genes are triggered by the environment in the way you speak. A dominant gene is one that is displayed in an organism while a recessive gene is one that is carried by an organism, may be passed to its offspring but does not show in the organism itself. This is how a person with black hair can have a blonde baby. Yes, a plant’s hardiness is genetic, but so is everything else. It is a plant’s genes a Lodge Pole Pine and not Spanish Moss or Christmas Cactus. If you rethink on the question a little and give a specific example of what you are talking about then we might be able to help you better.
Gobalist This thread is an off-shoot of the one on "Plant acclimatization". There I quoted the example of Wrightia Religiosa.
I just read that example and the way it is presented doesn't fit current understanding of evolution/genetics. Sorry, but that's just not the way it works. With you, or me, or any other living creature anywhere, the genes you get fertilization are the genes you die with. Your genes never learn anything and adaptation (at least as it is used in genetics and biology) is species wide, not a matter of individuals. If your interested, and you clearly are, give THIS a scan.
Gobalist, Many thanks. I see your link is enormous and no doubt will help to shed some light in my direction.
The latest Discover magazine has an interesting article on epigenetics. The way I understood it, was the ability to acquiring inheritable traits due to environmental factors. The genes are there but 'turned off' but the can be 'turned on' by an environmental factor for that generation and sometimes several that follow. The gene remains active despite a return to 'normal' environmental conditions. Now the article was written with vertebrates (mostly mammals in the article) in mind but some aspects may be true for plants as well. If it does apply to plants, it could manage sutle changes in environment, not gross changes. It's easy for us to establish what a minor or major change is in our environment from our perspective....ie. nutrition vs. epidemics. Nutrition may benefit from an epigentic change whereas the other requires natural selection. How does this work in plants? Disease, even within the same genus has grossly different effects (DED in American Elm vs. Siberian Elm, Chestnut Blight in American Chestnut vs. Chinese Chestnut) due to adaptations acquired through natural selection. I believe climate also requires natural selection to establish a hardier plant because it is a gross change in environment requiring major changes in plant physiology to protect it from climates (cold & seasonal changes in this case) in which it is not adapted. Simon
Simon, You brought out this point: "Disease, even within the same genus has grossly different effects" and I find it most interesting. Here we find very often that the immunity acquired by exposure to a disease suffices to protect us from future attacks. However the attacking organisms are always mutating and thus develop the ability to bypass our acquired immunity barrier. Wonder if we ever will become totally immune to the flu bugs. It is interesting to observe that immunity in one parent is seldom transmitted to the offspring, wonder why? Perhaps nature has an uncanny ability to balance out the human population against food supply.
A gentically acquired (ie. natural selection) resistance to a pathogen is a completely different mechanism compared to immunity acquired through an immune response. One is inheritable while the other is not. The flu is a class of virus containing many different genetic variations (hence the H1N, etc, etc.) Your acquired immunity to one flu bug does not result in immunity to another one. It's not the same flu that attacks the human population every year, mutating to overcome our defenses. It is a selected few that become dominant in the resevoir population for that year and then disappear in spring, to be replaced by a completely different selection the next year. A flu bug seen in 2002 may not show up for many years. Nature does have an uncanny ability to balance out the human population against food supply, it's called starvation, not disease, and it can happen to any overpopulated animal. Disease is more prevalent in overpopulated circumstances which can help control populations as well. This particular discussion does not relate well though, to plants. Simon
Simon Quote:Disease, even within the same genus has grossly different effects (DED in American Elm vs. Siberian Elm, Chestnut Blight in American Chestnut vs. Chinese Chestnut) due to adaptations acquired through natural selection At first glance, your statement appears correct and in line with Darwin's exposition on natural selection. Somehow I had some reservation on the nature of your presentation but couldn't get any specific pin point on its contradiction. It is wonderful how your subconscious can tackle problems without input from your conscious mind.Minutes ago my subconscious must have triggered my conscious thought to zoom in on this uneasiness I had harbored earlier. Here is the reason why I felt uneasy: DED (Dutch Elm Disease to elaborate for better understanding) affects species differently (American Elm vs. Siberian Elm). I guess it is the American Elm which was adversely affected. Is the reason due to adaptation acquired through natural selection? I see 2 possible scenarios here: (a)DED affects differently on both species because their dominant alleles giving rise to disease resistance though closely allied are nevertheless still genetically different (like occupying a different positioning in the genome structure). I am more inclined towards this idea of the genetic variance that gives rise to different levels of disease resistance. (b)DED affects them differently due to adaptations acquired through natural selection. If this is a proven scientific fact, then at some time eons away DED must have infected the Siberian Elm. The scenario would be most of them died and a handful survived. Like in the animal world, we build resistance to particular disease after an infection, so the plant may do likewise too. Proceeding from that point, this beneficial trait must have been transmitted to the future offspring to give the present day Siberian Elm its immunity to DED. I am surprised that nearly all the replies I had received on the subject dealing with genetics clearly stated that a phenotypic variation/adaptation is not inherited by the offspring. IF this were so, how come the Siberian Elm has acquired the resistance to DED. Unless an acquired trait is heritable, then natural selection doesn't even come into play. I always envision natural selection as a process to concentrate the population with species having higher levels of fitness until it becomes 100% concentrate. They claim that natural selection covers only the whole specie but not the individual but the fact remains that the individuals are the building blocks used in natural selection. Humans are the means and natural selection provides us with the end-product.
The elm example is a good one. I think both situations are possible. The Siberian elm may have been naturally resistant to DED by its genetic makeup. It may have never had the receptors to the disease or it may have lost them sometime after the two species diverged on their unique evolutionary paths. It is possible that the Siberian elms were once affected by the pathogen, but resistant individuals survived, reproduced and advanced creating a resitant species. (I do not know the specifics of these plants. We are just using them as an example of how evolution shapes species.) In response to your initial inquiry, jamkh, species arise through genetic mutation and natural selection. The potential to survive in a warmer or colder climate may exist in the gene pool. As climatic conditions change, plants in cooler areas with the genes necessary to survive in cool weather will prosper. In the warm areas, plants with genes that allow them to survive in warm conditions would thrive. The plants in cool areas may tend to lose the genes that would have allowed them to survive in warm climates. Mutations may arise in the population allowing them to spread into even cooler areas. Traits arising from mutation would not exist in the population left back in the warm areas. Over time through selection and mutation the species could evolve into different plants that may or may not be able to survive in the area where the species had its origins. Conditions on Earth are ever changing. All life is continually adapting to these changes. Over time plants (and other life forms) have diversified gaining and losing genetic traits to adjust to the changing environment. There may be individuals holding genetic traits that have been lost (or never developed) by most of the individuals of a particular species or population. These may be the survivors if environmental conditions change. Plants carrying genes that allow them to survive at the extremes of the plants environmental range or that resist disease or other adverse factors can be very valuable to plant breeders. Humans are playing a big role now in evolution because we probably make more genetic selections in plants than nature does by environmental factors.
Thank you very much, Eric. I believe very few of us could have explained this difficult subject without the scientific jargon and with such clarity that simple minds can grasp the essentials. I hope you are involved in lecturing and I for one would love to have been your student. I truely appreciate that you have finally put this nagging mental unrest to restful bliss.
