Evolution - niche and survival of the fittest

[Monkeymaniac]

According to TPRH, fitness is not how well an animal is physically adapted to the niche in the environment, or how well it can feed itself, but how successufl it is in passing on its alleles to future generations.

According to EK, niche is the way in which a species exploits its environment. And the theory of survival of the fittest predicts that one species will exploit the environment more efficiently, eventually leading to the extinction of other with the same niche.

1) Fitness defined by TPRH has exclusively to do with a species' ability to reproduce, where as survival of the fittest defined by EK is talking about adaptability. Which one is right?

2) And how do evolution, fitness, niche, and the theory of survival of the fittest all fit into the big picture? Especially, what is the relationship between fitness/survival of the fittest and evolution? Thanks in advance!

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[illegallysmooth]

According to TPRH, fitness is not how well an animal is physically adapted to the niche in the environment, or how well it can feed itself, but how successufl it is in passing on its alleles to future generations.

According to EK, niche is the way in which a species exploits its environment. And the theory of survival of the fittest predicts that one species will exploit the environment more efficiently, eventually leading to the extinction of other with the same niche.

1) Fitness defined by TPRH has exclusively to do with a species' ability to reproduce, where as survival of the fittest defined by EK is talking about adaptability. Which one is right?

2) And how do evolution, fitness, niche, and the theory of survival of the fittest all fit into the big picture? especially the relationship between fitness/survival of the fittest and evolution? Thanks in advance!

1. Fitness is the ability to pass on alleles by surviving and reproducing. This is consistent with both sources. An organism has to be able to survive to reproductive age, reproduce, and have viable offspring to have direct fitness.

2. Those who are the most fit will survive and leave more alleles in the next generation. This happens over many, many generations to produce the end result: evolution. Let's say there is a species A that relies on blending in with surroundings, which are mostly green, in order to survive. Species A is mostly green with some variation. There is competition within the niche with another species, B, which is more yellow in color. A is more green than B, blends in with surroundings better, gets eaten by predators less, survives more, and sends more of its genetic material into future generations. 100 years later, species A has taken over the niche and all of its members are consistently green in color.

Also, just want to note, this stuff is really, really important. I don't just mean important for the MCAT, but to understand medicine, science, research, etc as you continue in your education.

 

[UCB05]

From an evolutionary perspective, an individual who is superior at exploiting a niche but cannot reproduce is equally as UNfit as an extremely promiscuous individual that can't forage for food. The most fit is one that can not only outcompete others for survival in a niche, but also produce offspring (ensuring its genetic continuity) that can continue to exploit that niche.