Chapter 22

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Department
Biological Sciences
Course
BIOA02H3
Professor
Kamini Persaud
Semester
Winter

Description
Chapter 22 The Mechanisms of Evolution Evolutionary War Newts evolved the ability to secrete a paralytic poison from their skin, which deters most predators; some garter snakes have evolved resistance to it. 22.1 What Facts Form the Base of Our Understanding of Evolution - NATURAL HISTORY = THE SCIENTIFIC STUDY OF HOW DIFFERENT ORGANISMS FUNCTION AND CARRY OUT THEIR LIVES . - DARWIN WAS INTERESTED IN GEOLOGY AND NATURAL HISTORY ,BUT WAS PLANNING ON BECOMING A DOCTOR . - W ENT ON 5 YEAR VOYAGE ON HMS B EAGLE AND FOUND THAT THE SPECIES ON THE G ALAPAGOS ISLANDS WERE FOUND NOWHERE ELSE ,BUT WERE SIMILAR TO THOSE FOUND IN MAINLAND SOUTH AMERICA . - THIS THEORY FOR EVOLUTIONARY CHANGE WAS BASED ON TWO MAJOR PROPOSITIONS : S PECIES ARE NOT PERMANENT ;THEY CHANGE OVER TIME . T HE PROCESS THAT PRODUCES THESE CHANGES IN NATURAL SELECTION . - THOMAS M ALTHUS , AN ECONOMIST ,PUBLISHED A N E SSAY ON THE P RINCIPLE OF P OPN ABOUT HOW R OF HUMANN GROWTHR OF INCREASE IN FOOD PRODUCTION A ND UNCHECKED GROWTH INEVITABLY LEADS TO FAMINE . DARWIN AND W ALLACE WERE INFLUENCE BY THIS PAPER . - DARWIN BELIEVED DEATH RATES TO BE HIGH WO HIGH DEATH RATES , EVEN THE MOST SLOWLY REPRODUCING SPECIES WOULD QUICKLY REACH ENORMOUS POPULATIONS . - HE CAME UP WITH THE IDEA AND TERM NATURAL SELECTION , AND ARTIFICIAL SELECTION ALREADY EXISTED AND HE PRACTISED IT BECAUSE HE WAS A PIGEON BREADER . - DARWIN RECOGNISED THAT :INDIVIDUALS DO NOT EVOLVE ; POPULATIONS DO . - POPULATION = A GROUP OF INDIVIDUALS OF A SINGLE SPECIES THAT LIVE AND INTERBREED IN A PARTICULAR GEOGRAPHIC AREA AT THE SAME TIME . Adaptation has Two Meanings - ADAPTATION = BOTH THE PROCESSES BY WHICH THE USEFUL CHARACTERISTICS EVOLVE TO THE BEARERS THAT IS,THE EVOLUTIONARY MECHANISMS THAT PRODUCE THEM AND TO THE CHARACTERISTICS THEMSELVES . - THE CHARACTERISTICS ARE THE PHENOTYPIC CHARACTERISTICS THAT HAVE HELPED ORGANISMS ADJUST TO CONDITIONS IN THE ENVIRONMENT . - BIOLOGISTS COMPARE THE PERFORMANCE OF INDIVIDUALS THAT DIFFER BY TRAIT EX . DIFFERENT CON C ON TTX IN SKIN OF NEWT ) BY OBSERVING THEIR REPRODUCTION AND SURVIVAL IN THAT ENVIRONMENT . Population Genetics Provide an Underpinning for Darwins Theory - FOR A POPULATION TO EVOLVE ,ITS MEMBERS MUST HAVE HERITABLE GENETIC VARIATION ,WHICH IS THE RAW MATERIAL ON WHICH MECHANISMS OF EVOLUTION ACT . - PHENOTYPES = THE PHYSICAL EXPRESSIONS OF ORGANISM S GENES . - THE FEATURES OF A PHENOTYPE ARE ITS CHARACTERS EX. EYE COLOR . - THE SPECIFIC FORM OF A CHARACTER ,SUCH AS BROWN EYES , IS A TRAI. - A HERITABLE TRAIT IS A CHARACTERISTIC THAT IS AT LEAST PARTLY DETERMINED BY ITS GENES . - THE GENETIC CONSTITUTION THAT GOVERNS A CHARACTER IS CALLED ITS GENOTYPE ;A POPULATION EVOLVES WHEN INDIVIDUALS WITH DIFFERENT GENOTYPES SURVIVE REPRODUCE AT DIFFERENT RATES . - GREGOR M ENDEL STARTED POPULATION GENETICS ,WHICH HAS 3 MAIN GOALS : T O EXPLAIN THE ORIGIN AND MAINTENANCE OF GENETIC VARIATION . T O EXPLAIN THE PATTERNS AND ORGANIZATION OF GENETIC VARIATION . T O UNDERSTAND THE MECHANISMS THAT CAUSE CHANGES IN ALLELE FREQUENCIES IN POPULATIONS . - DIFFERENT FORMS OF A GENE , CALLED ALLELES ,MAY EXIST AT A PARTICULAR LOCUS . An allele occupies a fixed position or locus in the chromosome. At any particular locus, a single individual has only some of the www.notesolution.com
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