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What is the source of random variation upon which natural selection operates?
Wiki User
∙ 14y ago
In short, genetic mutations.
Most random genetic mutations have no bearing on the organism at all, but sometimes they do cause changes.
For example: A certain species of beetle may only be green. Its species is preyed upon by a particular bird that only likes green beetles. Then, one day a beetle is born with a genetic mutation that shifts its color from green to brown (this is the random mutation part). The bird doesn't eat the brown beetles. Therefore, the brown beetle is able to reproduce almost indefinitely, and then its offspring reproduce indefinitely, likely passing on the gene for the brown color. Eventually, the whole population of beetles shifts from green to brown and the birds find something else to eat (this is the natural selection part).
However, it works in the opposite way too. A perfect example would be a deer that is born albino. It will stick out like a sore thumb and be eaten quite quickly, leaving it no time to reproduce.
Evolution works in this way because natural selection itself is not random, though mutations are. An organism is constantly trying to adapt to its environment in a better way through natural selection, but its environment is always changing as well.
As for what causes the mutation, a number of things can occur (Its first quite important to know that DNA codes for amino acids, which are the building blocks of proteins, and the structure of the protein determines how it folds, and the fold determines the function). Sometimes, a base (that would be adenine, thymine, cytosine, or guanine) is simply left out or doubled, which causes a frame-shift in how the DNA code is read. This will subsequently change EVERY amino acid and make a completely different protein, which is sometimes functional and sometimes not. Furthermore, sometimes an entire gene is replicated, or even an entire chromosome. Sometimes, these replications don't do anything until another type of mutation effects on the genes/chromosomes and it creates a functional protein. For an example of this, Google "nylonase."
Its actually quite more complicated than this, but its impossible to answer it in full depth here. There are a lot of great videos on YouTube by user cdk007 that explain it a bit better, and of course there is always Wikipedia.
Wiki User
∙ 14y ago
Wiki User
∙ 12y agoHugh Jass
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What are the mechanisms of natural selection?
Basically, natural selection, genetic drift and gene flow into and out of population of organisms.
What constantly provides new variation for natural selection to act upon in a sexually reproducing popularion?
Firstly, mutation. In a sexually reproducing population recombination ( independent orientation of chromosomes and crossing over in meiosis and random fertilization ) is also a source of variation in populations.
How does genetic drift work?
Genetic drift is the term used for random evolutionary developments that have equal "survival-value" with respect to natural selection. Natural selection defines broad parameters for what kind of traits organisms existing in a certain environment should ideally have, but within these parameters there is a lot of room for random drift.
What is the main difference between natural selection and genetic drift?
The main difference to remember is that natural selection is a nonrandom process while genetic drift is a random process.
What causes allele frequencies to change during genetic drift?
Genetic drift is the spread of specific random variations throughout the gene pool in the absence of specific selection pressures. There's always random variation in the population, but there aren't always changes in the environment for the population to adapt to. So natural selection, in stead of moving the population towards adaptation, might select from that random variation to move 'sideways', as it were, to a state that's equally well-adapted to the environment as what came before, but different. As random variation may produce many variants that are, more or less, equally well-adapted to their environment, the direction of evolution that results is more or less random.
What are the Elements of the theory natural selection?
Replication random variation Non-random survival
Which is not part of darwins theory of natuarl selsction?
Random processes are not part of the theory of evolution by natural selection. Excepting random genetic mutation that provides the variation natural selection works on.
Why would natural selection not occur in population?
It has not reached carrying Capacity
Why is natural selection random?
No. Natural selection is the non-random survival of randomly varying replicators. The random variation part could be thought of as mutation and recombination that the non-randompart, natural selection, works with.
What are the mechanisms of natural selection?
Basically, natural selection, genetic drift and gene flow into and out of population of organisms.
How does natural selection affect variation?
Variation naturally occurs in populations as new traits arise from random mutations. However, through natural selection only those traits that are beneficial to the organism are passed on to the next generation. Any harmful mutations are naturally weeded out.
Why would natural selection not occur without genetic variations on species?
Without variation it would not be selecting, just random death of identical units.
Is random selection of prey essential in any model of natural selection?
No, many forms of natural selection have no connection to predation.
What are the 2 things necessary for evolution to occur?
Answer 1Two broad processes that make evolution possible are 1 : directional forces including mutation , migration and selection and 2: nondirectional forces that include random genetic drift , bottleneck effect , founders effect ,and chance variations .Answer 2Evolution is most commonly described as a combination of reproductive variation and differential reproductive success.Reproductive variation in itself is a "non-directional" phenomenon, that produces mostly random variations. Differential reproductive success (or: natural selection) is a "directional" phenomenon, that basically acts as a mechanism limiting the set of "directions" produced by random variation.
Why is natural variation important when it comes to evolution?
Only in the sense that natural selection needs variations in organisms to select from. Evolution could take place by random processes, such as genetic drift, or geographic processes, such as gene flow, but only natural selection causes the adaptive change that results in speciation.
What principles is not part of Darwin's original theory of evolution by natural selection?
Random processes are not part of the theory of evolution by natural selection.
What causes changes in allele frequency during genetic drift?
Genetic drift is the spread of specific random variations throughout the gene pool in the absence of specific selection pressures. There's always random variation in the population, but there aren't always changes in the environment for the population to adapt to. So natural selection, in stead of moving the population towards adaptation, might select from that random variation to move 'sideways', as it were, to a state that's equally well-adapted to the environment as what came before, but different. As random variation may produce many variants that are, more or less, equally well-adapted to their environment, the direction of evolution that results is more or less random.
