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Transcript
Modern Theory of Evolution…Part4 I. Darwin’s Weakness • Couldn’t explain why there was variation in populations. Didn’t understand genetics! Mendel’s theory was only dominant/recessive How do new characteristics appear? • • • Mutations Sexual reproduction II. Modern Theory of Evolution • Darwin’s theory of Natural Selection with Genetics! + III. Population Genetics • Species: A group of organisms that look alike and are capable of reproducing and creating fertile offspring. • Population: A group of individuals of the same species living in the same place at the same time. – Ex: homo sapiens in Hawaii – Ex: Stray cats at Kalaheo High School Population…continued – Can an individual respond to environmental change by adding or losing a trait? • – No, evolution is a change in a species over a long period of time in response to environmental changes. Populations evolve, not individuals!! Population Genetics…cont • Gene Pool: All the genes in a population at any given time. • Allele Frequency: Occurrence of alleles in a population – Remember, alleles are different forms of the same trait. IV. Adaptive Value Problems • Step 1: Define the population & count it! – ____Homo sapiens in this classroom • Step 2: Define the trait and alleles. – Trait: tongue rolling – Alleles: R-tongue roller, r-non tongue roller • Step 3: count up the genotypes in your population and the totals of each alleles. – RR:_______ Rr:______ rr: ______ Total R: ______ Total r:______ Total alleles:________ • Step 4: Determine the gene frequency of each allele. – Gene frequency of “R” =(# of R)/ Total – Gene frequency of “r” = (# of r )/ Total Let’s try another example… • Step 1: ____Homo sapiens in this classroom • Step 2: ____PTC tasting…T: taster, t: non-taster • Step 3: TT:_____ Tt:_____ tt:_____ Total T:____ Total t:___ Total alleles______ • Step 4: Determine the gene frequency for “T” and “t” V. So why do these FUN problems? • Adaptive Values: The value traits have in helping an organism survive. – Allele frequency is the same thing *High Value-90% *Medium value-50% * Low value-10% Camouflage in a tree frog Tongue rolling in humans Six fingers in humans Adaptive Values…cont. The more variety in a species (even neutral variations), the greater chance for.. 1. 2. Survival… Environment is always changing Variation fights off extinction Once trait is lost… 1. 2. It is really hard for a species to get it back. Traits may not be useful now, but who knows what will be needed in the future to survive.