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Author | Topic: What is the evolutionairy theory on the Giraffe? | |||||||||||||||||||||||
redstang281 Inactive Member |
Just curious. How did the giraffe acquire his long neck?
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joz Inactive Member |
quote: Um... Because being able to reach higher up the tree is an advantage when you eat leaves maybe? Thus those with longer necks would tend not to starve to death and therefore pass a genetic tendency for long necks down to their offspring...those with short necks would starve and not pass on their genes....
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redstang281 Inactive Member |
quote: So if the ones with short necks would starve, then how did baby giraffe's survive long enough to grow long necks(so that they could survive long enough to pass on genes?)
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joz Inactive Member |
quote: You seem to be neglecting the common mammalian trait of nurturing our young....
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redstang281 Inactive Member |
quote: Explain.
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joz Inactive Member |
quote: Did you have a mother?
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redstang281 Inactive Member |
quote: I want to know in what way the giraffe took care of the baby giraffe to help him survive and eat the leafs on the top of the tree that only the full grown giraffe could reach. I think I know what you are going to say, but I want you to say it, not me. [This message has been edited by redstang281, 12-14-2001]
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joz Inactive Member |
quote: Your mother took care of you I presume? If so then she was displaying the shared mammalian trait of nurturing your offspring... Oh and you know what giraffes are mammals as well.... The mechanism by which the help is given is immaterial it is sufficient that the help is given...
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mark24 Member (Idle past 5195 days) Posts: 3857 From: UK Joined: |
The way evolution works is to offer up random mutations to non random natural selection.
This means that ANYTHING that would increase the survival of an individual, would mean a greater chance of surviving to mate & therefore pass on those genes. In the case of a Giraffe, lets assume three scenarios ; 1/ A light drought. The young Giraffes would be able to survive on their mothers milk whilst the mother was able to obtain both food & water. If food is plentiful enough, & leaves remain on lower branches, then there’s no particular natural selection going on here. The shorter necked individuals get as much food as the longer necked examples. All the young Giraffes are amply fed by their mothers milk. 2/ A medium drought. The longer necked examples are able to get the upper leaves when the lower leaves are gone. They are still able to produce milk for their offspring, who survive. The shorter necked examples can’t get adequate food for both themselves & their young, their milk dries up & the young die. However, they, along with weaned adolescents are able to feed themselves. There is adequate lower level foliage. In this scenario, although the short necked adults survived, their young did not. As a result ALL surviving young had the long necked gene. As a result, there is a greater percentage of individuals with the long necked gene at the end of the year. 3/ A hard drought. No Giraffes are able to sustain milk for their young & all young die. The short necked Giraffes aren’t able to feed themselves either, & die, along with the adolescents. Only the long necked adults survive, by virtue of their long necks & greater ability to feed themselves. This year has been a waste as far as offspring goes, but next year sees a reduced population entirely armed with the magic survival gene long neck. All offspring from now on will have the gene & what began as a mutation in an individual, has now entered the general population. ------------------Occam's razor is not for shaving with.
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nator Member (Idle past 2170 days) Posts: 12961 From: Ann Arbor Joined: |
quote: I can answer yout question with one word, actually. Milk.
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redstang281 Inactive Member |
quote: I thank Mark for giving me a real answer. The giraffe baby would suck the mother's milk until it is big enough to reach the tree branches. So you are saying that the environment presents a need that must be forfilled in order for a species to survive? Which would mean in this case the environment presented the giraffe with vegetation above his head and the giraffe had to develop a longer neck to reach the vegetation or else it would die out?
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mark24 Member (Idle past 5195 days) Posts: 3857 From: UK Joined: |
quote: Sorry redstang, not sure if this was aimed at me or Joz. But anyway..... No. The environment is able to throw all sorts of things at the Giraffe, famine & drought among them. ANYTHING that gives a survival advantage to an individual will allow that individual to compete better for food, mates etc & pass those traits on. If the're good enough, they'll become the norm, given enough generations. I see what you're getting at re. HAVING to get long necks or die. If they couldn't get access to as much food as they do, then they would either be unsuitable for the habitat that they live in & become extinct there, or live where there is less competition for food. The fact it has a long neck, ALLOWS it to exist in habitats of drought & famine, enhancing the geographical diversity of that species, thus contributing directly to the success of that species. The question then arises, what happens to species like antelopes that don't have long necks. Surely they would die too? No. They have adaptions to the environment unique to themselves (incidentally there are species of long necked antelope, though not approaching that of Giraffes). this could be a different diet, a migratory habit etc. Incidentally, in the examples I gave, I tried to show how natural selection would work when a long neck was compared to purely a food variable. It also has the advantage of spying predators from far enough away that they don't become a threat. Thus "long necked" young are more likely to survive even when food is plentiful. Its entirely possible that the driving environmental factor behind long-neckedness was predator evasion. & that as a side advantage, they were able to get to higher branches. ------------------Occam's razor is not for shaving with.
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redstang281 Inactive Member |
quote: I must commend you on how well your informantion has been thought out. So this would mean that the during the time the giraffe was evolving it had a survival advantage over the antelope. So therefor, antelope wouldn't have been able to survive as well as the giraffe in certain environments. Why didn't the antelope evolve the longer neck so it could have a survival advantage as well?
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Mister Pamboli Member (Idle past 7577 days) Posts: 634 From: Washington, USA Joined: |
quote: Well the answer has already been given in part - antelope and other animals under the same pressures developed other means of survival. The giraffes neck is only one of many solutions. Bear in mind that if all grazing animals developed long necks there would be more competition for the treetop treats and this would be yet another selective pressure. Some antelope do have quite long necks and others can stand quite elegantly on their hind legs to graze from trees. BTW, were I a literal creationist, I would need to ask myself - if one was to design an animal which has to survive on a boat for 40 days, would one give it 2-metre legs and a 3-metre neck? I suspect not.
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redstang281 Inactive Member |
quote: Oh, I understand that it's one of the many solutions to survival. But if gives them a survival advantage then why didn't all animals develope it so they could all have better means of surviving?
[b] [QUOTE]Bear in mind that if all grazing animals developed long necks there would be more competition for the treetop treats and this would be yet another selective pressure. Some antelope do have quite long necks and others can stand quite elegantly on their hind legs to graze from trees.[/b][/QUOTE] But if they have a long neck that shouldn't limit them to only eating vegitation from the top. It should only give them a greater range to select from. A giraffe does have to drink water on the ground, so he is capable of lowering his neck. So if vegitation wasn't left at the top from other long neck animals eating it, then he could certainly eat near the middle or the bottom.
[b] [QUOTE]BTW, were I a literal creationist, I would need to ask myself - if one was to design an animal which has to survive on a boat for 40 days, would one give it 2-metre legs and a 3-metre neck? I suspect not.[/b][/QUOTE] I disregard this only to keep the focus on the post to my original question. [This message has been edited by Percipient, 12-15-2001]
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