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AP BIOLOGY NAME:____________________________________ DATE:__________________________PER:______ CH. 23 (A): EVOLUTION of _________________ [combining the work of ____________ with _____________!] Recall, EVOLUTION does not act on ________________, but ______________ _______________ DOES ACT on ________________! SO, as natural selection acts on individuals, those with adaptations __________ for their environment or environmental changes, will survive & ________________, therefore affecting the ALLELES present in the ________ _________ of a particular __________________! MACROEVOLUTION: the larger level at which we can study _______________ change on a __________ level of a whole ___________. MICROEVOLUTION: the smallest level at which we can study _____________________ change. As _____________ in the genetic makeup of a __________________ occurs from __________________ to ________________. What makes EVOLUTION possible? ________________________ Caused through: _________________ SEXUAL RECOMBINATION ( o produces the variation in ___________ ___________ that contributes to the individual heritable differences in a ___________________. GEOGRAPHIC VARIATION: a type of _______________ _________________ (between ___________________) when organisms of the same __________ exhibit _____________/______________ especially when separated into different & separate _________________. -1- MUTATIONS: originate from changes in the _________________ sequence of _________, resulting in _________ genes & _________ alleles. o can have a significant impact on _________________. "POINT MUTATION": a change of as little as ____ base in a gene. MUTATION RATES: o Mutation rates tend to be ________ in plants & animals. o But __________, especially those with RNA, have much higher mutation rates. Can result in drug-resistant __________, like HIV. SEXUAL RECOMBINATION: (as a result of sexual ___________________) o almost all _________________ variations based on genetic differences result from ___________________ shuffling of the existing alleles in a ___________ ___________. Ex: _______________ & ____________ have high _______________ rates & extensive _________________. produces _________________ that make adaptation possible... ...BUT, does NOT create new alleles/genes & doesn't change their frequency, ONLY "re-shuffles" the alleles in the _________ _________ of a population. Recall, individual organisms DO ______ EVOLVE!!!...but ___________ DO!!! o Although, _____________ ______________ does act on individuals, because each individual's ___________ affect it’s ______________ & reproductive success compared to other individuals... o ...BUT, the EVOLUTIONARY IMPACT of natural selection is ONLY apparent in the changes in a POPULATION (____________) of organisms over __________! o EX: Cuban tree snails (Fig.23.1) They have _______________ ________________ (__________________ among individuals within a _____________) as a result of genetic differences.... ....suppose they live in an environment of red grasses...causing snails with more _______ colored patterns (better camouflaged against their surroundings = “more ______”) to be _________ likely to survive, THUS, the proportion of snails with that color pattern will tend to ______________ from one _________________ to the next... -2- ...BUT, _________________ CANNOT evolve themselves to survive (snails cant "decide" to change their patterns to the more red-color)... ...THUS, the ________________/____________, NOT its _______________ members, EVOLVES over time, as some traits become _________ common within the population, and others become _________ common. POPULATION GENETICS: Studies the _________________ changes in _________________ over ___________. o Individuals in a population must have _______________ ________________ in order for _________________ to occur (via _________________ ________________), BUT, does the presence of genetic variation, guarantee evolution will occur??? _________...WHY? ______________________________________________________ POPULATION: a localized group of _________________ that are capable of ___________-_______________ & producing ____________/____________ offspring = same ____________, same ___________, & can ________________ & produce _____________ offspring! [see Fig.23.3] o The same ___________ can have different ________________ because they are ________________ from each other, thus rarely exchange __________/______________ by breeding. GENE POOL: a population’s genetic ______________. the "pool" of available genes/_____________ present within a population (in an __________) at any one time; consists of all the possible, available ____________/traits. -3- ALLELE FREQUENCY: the frequency/proportion/”__________________” of certain alleles within a specific ___________________. The frequency of specific alleles can vary within different _________________. For example: Cuban snails… o In red-grass areas, the alleles for ________-patterns are found at _______________ frequencies/__________ common within that particular ___________________, while the alleles for other patterns are found at _______________ frequencies/__________ common within that particular ___________________. o In green-grass areas, the alleles for ____________-patterns are found at _______________ frequencies/__________ common within that particular ___________________, while the alleles for other patterns are found at _______________ frequencies/__________ common within that particular ___________________. The events & trends that occur within _________________ GENETICS, leads to ___________________ of a species as a whole, over ___________...SO, to study & understand EVOLUTION, you have to study-understand __________________ _________________! The HARDY-WEINBERG PRINCIPLE: o Recall, we answered the question, “does the presence of genetic variation, guarantee evolution will occur?” _______! o One way to assess IF natural selection or other factors are causing evolution at a particular LOCUS, is to determine what the genetic makeup of a _________________ would be if it were ________ evolving at that ___________...THEN, we COMPARE that to a real ________________, & if there are _______ differences, then we can conclude that the real population is NOT ____________...however, if there ARE differences, then the real population IS ______________, & we can try to figure out what are the causes… WHY are we looking at a particular LOCUS??? _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ -4- The HARDY-WEINBERG THEOREM: (RE-READ section in bk!) o Describes a ______________ whose __________ ___________ is NOT ____________. o the principle that states that the frequencies of ____________ and genotypes in a population (___________ ___________) remains ______________ from generation to generation, provided that only Mendelian segregation (including random fertilization) and recombination of alleles are at work…such a gene pool is said to be in _______________________________________________. The HARDY-WEINBERG EQUILIBRIUM: (RE-READ section!) o the condition describing a non-______________ _________________; population is in ______________ _________________. Instead of thinking about what possible genetic combinations can result from only ____ cross (____________ ____________), we must now consider _______ the possible genetic ________________ that can result within an entire ________________! SEE Fig.23.6 AND 23.7 If a population is in Hardy-Weinberg equilibrium & its members mate randomly generation after generation, alleles & genotype frequencies would remain ______________. The system operates somewhat like a deck of cards: no matter how many times you shuffle the deck and deal out hands/or pairs (alleles). The cards in the amount and types of cards in the deck remains the __________ (_________ ___________; allele frequency); aces won’t magically change into another card. In the same way, the “shuffling” of a population’s _________ __________ over the generations cannot, in itself, ___________ the frequency of alleles present in the gene pool. The HARDY-WEINBERG THEOREM is used to statistically ____________ allele frequency of certain __________ within a specific ________________. CONDITIONS for Hardy-Weinberg Equilibrium: o the Hardy-Weinberg theorem describes a _________________ population that is _______ evolving… o …BUT, in real populations, allele and genotype frequencies ______ change over time… -5- o …this is because the 5 conditions required for non-evolving populations (i.e.___________-______________ _________________) are ___________ met for long in nature: 1) Extremely large population size. The smaller the population, the greater the role played by chance fluctuations in allele frequencies from one generation to the next, known as _____________ __________. 2) No gene flow. Gene flow, the transfer of alleles between _______________ can alter allele frequencies. 3) No mutations. By introducing or removing genes from chromosomes or by changing one allele into another, ________________ modify the __________ ___________. 4) Random mating/random fertilization. If individuals preferentially choose __________ with certain genotypes, including close relatives (inbreeding), random mixing of gametes does not occur. 5) No natural selection. Differential survival and _______________ success of individuals carrying different genotypes will alter ____________ frequencies. in order for a population to be in Hardy-Weinberg equilibrium, these 5 conditions must be met, which is _______ likely in nature… …SO, IF these 5 conditions are NOT met, which is ___________, then __________________ occurs!!! Though natural populations rarely if ever are in true Hardy-Weinberg ________________, the rate of evolutionary change in many populations is so __________ that these populations ____________ to be close to equilibrium. This enables us to obtain approximate estimates of ____________ & _______________ frequencies. Recall, natural populations rarely, if ever, are in true Hardy-Weinberg ________________...but because evolutionary change occurs so slow, populations can appear to be close to equilibrium… thus, the H-W-theorem & equation enables us to obtain approximate estimates of ____________ & _______________ frequencies. o SEE “Population Genetics & Human Health” section as an example APPLICATION: the H-W equation can be used to ________________ the % of the population carrying an _____________ for an inherited disease. -6- GENETIC DRIFT: unpredictable fluctuations in allele ________________ from 1 generation to the next because a population is finite in size (not infinite). ~ SEE FIGURES in BOOK!!! o can result in loss of alleles by ____________. o over time, drift tends to ____________ genetic variation through losses of alleles from the ___________ ___________ o 2 situations can increase the likelihood that genetic drift will have a large impact on a population: bottleneck effect & founder effect BOTTLENECK EFFECT: a type of genetic drift that results from a sudden change in the environment, i.e. a ____________ ______________ or even ____________ ____________, like a flood or fire...that reduces the size of a _________________, and the surviving population's __________ __________ may not be reflective of the original population's gene pool. o by chance, some alleles may be more common among the survivors, while others are less common or even eliminated altogether. o SEE FIGURES in BOOK!!! FOUNDER EFFECT: a type of genetic drift that occurs when a few individuals become isolated from a larger population (i.e. island formation), with the result that the new population's gene pool is not reflective of the original population. A Summary of the EFFECTS of GENETIC DRIFT: 1) ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ 2) ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ -7- 3) ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ 4) ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ GENE FLOW: genetic additions to or subtractions from a population resulting from the _______________ of fertile individuals or gametes. o tends to reduce the ________________ between populations. the 3 major factors that can alter allele frequencies & cause the most evolutionary change are ______________ _______________, GENETIC DRIFT, & GENE FLOW. RE-READ "A Closer Look at Natural Selection" + "Evolutionary Fitness" or "Relative Fitness" RE-READ "The Key Role of Natural Selection in Adaptive Evolution!!! RE-READ “Case Study: Impact of Genetic Drift on the Greater Prairie Chicken” RE-READ “Sexual Selection” RE-READ “Why Natural Selection Cannot Fashion PERFECT ORGANISMS” -8-