AP Review Chapters 22-24

Fast Facts Lamarck placed fossils in an evolutionary context Jean Baptiste Lamarck: published his theory of evolution in 1809 Remembered for his mechanism of evolution - first idea was use and disuse - second was inheritance of acquired characteristics

Fast Facts Natural Selection: populations can change over time if individuals with certain traits have more offspring than other individuals - nature chose what features are beneficial and give an increased chance of survival The history of life is like a tree. - each fork of the tree is an ancestor who is common to others from that fork

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Fast Facts N.S occurs between individuals and the environment, but only populations (not individuals) evolve. N.S. can amplify or diminish only heritable variations (not acquired characteristics) Evidence of N.S. provides evidence for evolution - natural selection causes the evolution of resistance to insecticides

Fast Facts - only a few insects are resistant to the first wave insecticide - those reproduce and pass on the gene to the second generation - eventually the whole population will be resistant

Fast Facts Homology: similarity on characteristics resulting from common ancestry Anatomical Homologies - the forelimbs of mammals have the same skeletal structures (homologous structures)

Fast Facts - vestigial structures: structures of marginal, if any, importance to the organism -ex. pelvis and leg bones of snakes

Fast Facts Molecular Homologies: all species of life use the same machinery of DNA and RNA - the more similar the animals, the more similar the genetic material

Fast Facts Embryological Homologies - all vertebrate embryos have pharyngeal pouches some time in their development.

Sample Questions The problems of survival of animals on land are very different from those of survival of animals in an aquatic environment. Describe four problems associated with animal survival in terrestrial environments but not in aquatic environments. For each problem, explain an evolutionary solution.

Fast Facts The Hardy-Weinberg theorem describes a nonevolving population - the frequencies of alleles and genotypes in a population’s gene pool remain constant unless acted upon by outside factors - the shuffling of alleles has no effect on a population’s gene pool

Fast Facts P + Q = 1 p2 + 2pq + q2 = 1 - large population size - no migration - no mutations - random mating - no natural selection

Fast Facts Microevolution: the generation-to-generation change in a population’s frequencies of alleles The two main causes of microevolution are genetic drift and natural selection Genetic drift: a change in a population’s allele frequencies due to chance

Fast Facts Bottleneck effect: genetic drift resulting from the reduction of a population such that the surviving population is not representative of the original population

Fast Facts Founder effect: genetic drift in a new colony - a few individuals from a larger population colonize an isolated new habitat - ex. from mainland to island

Fast Facts Natural Selection: the differential success in reproduction Gene flow: genetic exchange due to the migration of fertile individuals or gametes between populations Mutation: a change in a organism’s DNA

Fast Facts Diploidy and balanced polymorphism preserve variation Genetic variation can be hidden from being selected against by the use of heterozygotes Balanced polymorphism: the ability of natural selection to maintain stable frequencies of phenotypic forms

Fast Facts - ex. heterozygote advantage as seen in sickle-cell disease - ex. frequency-dependent selection: survival and production of any one morph declines if that phenotype becomes too common in a population

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Fast Facts Evolution must also explain macroevolution: the origin of a new taxonomic group Speciation: development of a new species The fossil record displays two patterns of speciation: anagenesis and cladogenesis Anagenesis: the accumulation of changes associated with the transformation of one species into another Cladogenesis: the budding of new species from a parent species that still exists.

Fast Facts Species: means “kind” or “appearance” - we distinguish plants and animals by differences in appearance

Fast Facts Prezygotic and postzygotic barriers isolate the gene pools of biological species Prezygotic barriers: impede mating between species or hinder the fertilization of the ova Habitat isolation: two species live in different habitats; low occurrence of interaction Behavioral isolation: special signals that attract mates, along with elaborate behaviors unique to a species

Fast Facts Temporal isolation: two species breed at different times (day, seasons, years) Mechanical isolation: anatomically incompatible Gametic isolation: gametes rarely fuse to form a zygote; sperm might not be able to travel to the ova

Fast Facts Postzygotic barriers: prevent the hybrid zygote from developing into a viable, fertile adult Reduced hybrid viability: hybrids are completely or largely sterile - Donkey + horse = mule Hybrid breakdown: the first generation of hybrids are fertile, but as those mate with one another, the offspring of the next generation are sterile

Fast Facts There are two modes of speciation based on how gene flow among populations is initially interrupted Allopatric speciation: speciation takes place in populations with geographically separate ranges Sympatric speciation: speciation takes place in geographically overlapping populations

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Fast Facts The punctuated equilibrium model has stimulated research on the tempo of speciation

Sample Question Define, discuss, and give an example of how each of the following isolating mechanisms contributes to speciation in organisms. a. Geographical barriers b. Ecological (including seasonal) isolation c. Behavioral isolation d. Polyploidy