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Natural selection notes

Natural selection notes - 1 NATURAL SELECTION DARWIN'S...

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NATURAL SELECTION; DARWIN’S GRAND IDEA =Differential reproductive success among genetically- based phenotypes -Due to relationship between phenotype and environment EXPLAINED ADAPTATION =Any heritable trait that increases the fitness of an individual compared to others in the same population without the trait FITNESS: CURRENCY OF EVOLUTION *Reproductive success of individuals/phenotypes compared to others in a population =Relative reproductive success FITNESS: CURRENCY OF EVOLUTION = RELATIVE REPRODUCTIVE SUCCESS OF PHENOTYPES WITHIN POPULATIONS TERMS: REPRODUCTIVE SUCCESS RELATIVE DIFFERENTIAL THE IMPORTANCE OF THE IDEA OF NATURAL SELECTION: -EXPLAINED ADAPTATION -ANY HERITABLE TRAIT THAT INCREASES THE FITNESS OF AN INDIVIDUAL COMPARED TO OTHERS IN THE SAME POPULATION WITHOUT THAT TRAIT HOW DID DARWIN COME TO IT? OBS1: ALL ORGANISMS HAVE POTENTIAL FOR VERY RAPID INCREASE IN NUMBERS - IMPORTANCE OF MALTHUS (OVERHEAD OF OBSERVATION) OBS2: YET, NATURAL POPULATIONS TEND TO BE STABLE IN SIZE DED: MANY MORE OFFSPRING ARE PRODUCED THAN SURVIVE ___________ OBS 1: VARIATION EXISTS IN THE TRAITS OF THE MEMBERS OF MOST SPECIES OBS 2: SOME OF THIS VARIATION IS INHERITED DED: INDIVIDUALS THAT INHERIT CHARACTERS THAT CONFER HIGHER REPRODUCTIVE SUCCESS WILL TEND TO REPLACE THOSE ASSOCIATED WITH LOWER REPRODUCTIVE SUCCESS ******* STRUGGLE FOR EXISTENCE; RESOURCES IN SHORT SUPPLY HOWEVER: NS DOES NOT WORK ONLY THROUGH COMPETITION FOR LIMITED RESOURCES FOR EXAMPLE SELECTION BY PREDATORS 1
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REMIND, BUT DO NOT DO…… AN EXAMPLE; A MOTH AND LEAPING LORDS Biston betularia 120 YR AGO, FIRST MELANIC FORM =INDUSTRIAL REVOLUTION KETTLEWELL asked two questions -DIFFERENTIAL REPRODUCTIVE SUCCESS? -CAUSE WHAT IS MISSING HERE TO REALLY DEMONSTRATE EVOLUTION BY NATURAL SELECTION? NATURAL SELECTION (A) SELECTION AGAINST DELETERIOUS RECESSIVES (1) COMPLETE (LETHAL) SELECTION (2) PARTIAL SELECTION (B) SELECTION AGAINST DOMINANT DEFECTS (1) COMPLETE (LETHAL) SELECTION (2) PARTIAL SELECTION (C) SELECTION FAVORING NEW BENEFICIAL MUTATIONS (D) DIFFERENTIAL SELECTION OF HETEROZYGOTES (E) SELECTION ON QUANTITATIVE TRAITS (1) DIRECTIONAL (2) STABILIZING (3) DISRUPTIVE (4) FREQUENCY-DEPENDENT (F) SELECTION AGAINST DELETERIOUS RECESSIVE ALLELES (1) COMPLETE (LETHAL) SELECTION =100 % SELECTION AGAINST THE RECESSIVE = Genetic death, not physical death DIFFERENTIAL REPRODUCTIVE SUCCESS IN WHICH HOMOZYGOUS RECESSIVE INDIVIDUALS HAVE ZERO REPRODUCTIVE SUCCESS POPULATION OF 48 MALES AND 48 FEMALES= 48 MATINGS -WORK TABLE SHOWING NUMBER OF MATINGS OF EACH TYPE 2
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-USE IT TO LINK TEXT TABLES 4.1 & 4.2 -NOTE HOMOZYGOUS RECESSIVES WOULD NOT HAVE REPRODUCED -RERUN PROCESS WITH 36 MATINGS (# LEFT AFTER aa ELIM) -NOTE DECREASE IN aa IN PROGENY OF THE MATINGS .... ALLELE FREQUENCY HAS DECLINED TO 33.33% IN POP CONTINUE OBSERVATION OF DECLINE IN DELETERIOUS RECESSIVES TABLE 5.3 FIGURE 5.1 VERY VERY difficult to eliminate a deleterious recessive -hidden in heterozygote -MANY HARBORED IN POPULATIONS IN LOW FREQUENCY HUMANS: COUSIN MATINGS; 1-6 PER PERSON DROSOPHILA SECOND CHROMOSOME: -33% HAVE ONE OR MORE LETHAL OR SEMI-LETHALS
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