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2. If the presentation at time t is assigned to C1 instead of C0 then, for each i such that di(t)= 1, replace the corresponding weight by the next lowest weight (for uniform intervals, the new weight is wi - D). |
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We cannot yet fruitfully discuss the merits of this plan in comparison to alternatives; we can only note that the order in which t00 tests the elements of  does indeed depend upon the information it receives. That is, the trajectory through  is conditional on the outcomes µE(A),  , of prior tests. |
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4. A Complex Natural Adaptive System |
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Here we will look at biological adaptation via changes in genetic makeupthe first of a series of progressively more detailed examinations. This section will present only biological facts directly relevant to adaptation, with a caveat to the reader about the dangers of unintentional emphasis and oversimplification inherent in such a partial picture. |
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It is a familiar fact (but one we will delve into later) that every organism is an amalgam of characteristics determined by the genes in its chromosomes. Each gene has several forms or alternativesallelesproducing differences in the set of characteristics associated with that gene. (E.g., certain strains of garden pea have a single gene which determines blossom color, one allele causing the blossom to be white, the other pink; bread mold has a gene which in normal form causes synthesis of vitamin B1, but several mutant alleles of the gene are deficient in this ability; human sickle cell anemia results from an abnormal allele of one of the genes determining the structure of hemoglobininterestingly enough, in environments where malaria is endemic, the abnormal allele can confer an advantage.) There are tens of thousands of genes in the chromosomes of a typical vertebrate, each of which (on the evidence available) has several alleles. Taking the set of attainable structures to be the set of chromosomes obtained by making all possible combinations of alleles, we see that contains on the order of 210,000@ 103000 structures for a typical vertebrate species (assuming 2 alleles for each of 10,000 genes). Even a very large population, say 10 billion individuals of that species, contains only a minuscule fraction of the possibilities. |
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The enormous number of possible genetic structuresgenotypesfor a single vertebrate species is an indicator of the complexity of such systems, but it is only an indicator. The basic complexity of these systems comes from the interactions of the genes. To see just how extensive these interactions are, it is worth |
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