How do you define the word Evolution?

Evolution, simply put, is Change. Biologically, it is change in allele frequencies between successive generations, sometimes leading to phenotypic change. Nb. Natural selection is not the only mechanism (eg. sexual selection, genetic drift also apply).PS.( not incl. in 90 words!) this is my first post to EvC! been a lurker for a few months now, and finally decided to shrug off my cloak of invisibility!

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So intimate that your hand upon my chest is my hand,
so intimate that when I fall asleep it is your eyes that close.
- Pablo Neruda

An ALLELE is just an alternate form of a gene. there aren't necessarily only two forms; many genes have hundreds of alleles.A LOCUS is basically a position on a chromosome. This applies to genes, short DNA sequences, or even base pairs; and almost never changes, unless a translocation occurs, which is rare.To say " Alleles at a certain locus" is basically the same as saying "Alleles of a certain gene", for most intensive purposes.If you remember, we each get a set of chromosomes from each of our parents, 23 + 23 = 46 chromosomes, wherein you have two chromosome 1's, two chromosomes 2's, etc. Each chromosome from your father will have a counterpart from your mother - these corresponding chromosomes are HOMOLOGOUS to each other.With the above information, you can see that my definition does not bear the restrictions you said it did.a point to make tho', is that evolution is NOT a "change of gene" from parent to offspring, every generation. If that were the case, no advantageous allele would ever gain a foothold since it would be replaced, almost immediately! This "change in gene" i.e. a mutation would occur, for instance, once off. The offspring that has this mutation (possibly advantageous) would then pass it on to their offspring.maybe if you look at it from the population perspective, and not the individual perpective it would make more sense.a change in allele frequencies, due to, say, positive selection, means the increase in frequency of an advantageous allele in a population, resulting in a decrease in frequency of other alleles of that gene.hope this clears a few things up. altho' very hard to explain these things in 90 words.

One could say that a mutation could be regarded as the "first step" in evolution.The occurrence of a new allele in a population (thro' mutation in one individual) would, technically, change the allele frequencies of that gene in the population; albeit to the tiniest extent.The point to make, however, is that mutation is not the be-all and end-all of evolution.