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York University
PSYC 1010
Doug Mc Cann

BIOLOGY APRIL EXAM REVIEW NOTES 1 Biology April Exam Review Notes Chapter 3 – Selection, biodiversity & Biosphere 3.1 – Biodiversity  Biodiversity o Number of species of organisms  Cell – smallest form of live that can live and reproduce  Multicellular organism – individual with interdependent cells  Population – individuals of same species in same area  Community – populations of all species in same area  Ecosystem – All communities in shared physical environment  Biosphere – All regions of earth that sustain life  Autotrophs o Self nourishing o Most plants o Synthesize C using CO 2  Heterotrophs o All animals o Obtain C from living hosts or from organic molecules in products, wastes, or remains of dead organisms  Chemotrophs o Chemical nourishment o Obtain energy through oxidation of inorganic or organic substances  Phototrophs o Obtain energy from light  Modes of Nutrition among living species o Chemoautotrophs o Chemoheterotrophs o Photoautotrophs o Photoheterotrophs 3.2 – Selection  Selection o Force or phenomenon effects survival of individuals o Large population exposed to lethal factor -> only resistant individuals survive to reproduce o Resistance heritable o Key factors: Selective force & capacity for explosive population growth 3.3 – Evolution  Evolution o Gradual change in the characteristics of population over time  Darwin’s Theory o Individual organisms in a population vary in many heritable traits o Competition for resources means only some offspring survive 1 BIOLOGY APRIL EXAM REVIEW NOTES 2 o Organisms with traits that give advantage, are more likely to survive & reproduce o Favorable traits pass on to offspring o Number of organisms in species with favored traits will increase over time 3.4 – Biosphere  Climate o Weather conditions prevailing over an extended period of time  Intensity of solar radiation varies on earth because of it’s spherical shape  Near poles: radiation travels long distance and strikes large surface area  Near equator: Radiation travels short distance and strikes small SA  Earths tilt, 23.5, is responsible for seasonal variation 3.5 – Biotic factors  Interactions between organisms  Competition  Parasitism Chapter 17 – Microevolution: Genetic Changes within Populations  Microevolution – Heritable change in the genetics of a population 17.1 – Variation in Natural Populations  Phenotypic variation o Differences in appearance or function that are passed on from generation to generation o Caused by: genetic differences between individuals, environmental factors or interaction between environment and genetics  Quantitative variation o Individuals differ in small, incremental ways o Length, number, height, weight, etc  Qualitative o Exist in two or more discrete forms o Polymorphism  Existence of discrete variants of a character  I.e. white goose, black goose  Genetic variation o Genetic material molded my microevolutionary processes o 2 sources: 1. Production of new alleles  Mutation 2. Rearrangement of existing alleles  Crossing over between homologous chromosomes during meiosis  Independent assortment of nonhomologous chromosomes during meiosis  Random fertilization between genetically different sperm & egg 2 BIOLOGY APRIL EXAM REVIEW NOTES 3 17.2 – Population Genetics  Population genetics o Describe genetic structure of population  Gene pool o Sum of all alleles on all gene loci in all individuals  Genotypic frequency o Percentage of individuals possessing each genotype  Allele frequency o Relative abundance of each of the different alleles  Null model o Predict outcome if a particular factor had no effect o Theoretical reference point  Hardy-Weinberg principle o Condition under which sexually reproductive organisms achieve genetic equilibrium o Genetic Equilibrium – neither allele nor genetic frequencies change in succeeding generations o 5 conditions: 1. No mutation 2. Closed to migration 3. Infinite size 4. All genotypes survive and reproduce equally well 5. Mate randomly 17.3 – Agents of Microevolution  Mutation o Heritable change in DNA o Deleterious mutation  Alter individuals structure, function or behavior in harmful way o Lethal mutation  Cause death in organisms carrying them o Neutral mutation  Neither harmful nor helpful o Advantageous mutation  Some benefit on individual who carries it  Gene flow o Organisms or their gametes move from one population to another  Genetic drift o Chance event cause allele frequencies to change unpredictably o Population bottleneck  Stressful factor that kills many individuals and eliminates some alleles from a population o Founder effect 3 BIOLOGY APRIL EXAM REVIEW NOTES 4  Few individuals colonize, start a new population, and thus carry only a small sample of parent population’s genetic variation o Conservation biology  Endangered species experience severe population bottleneck and results in genetic variation  Natural selection o Process by which traits become more common in subsequent generations o Relative fitness  Number of surviving offspring that an individual produces compared with the number left by other in the populations o Directional selection  Individuals with phenotypes near one extreme have highest relative fitness  Mean phenotype changes but variability may stay the same o Stabilizing selection  Individuals with intermediate phenotypes have highest relative fitness  Mean phenotype does not change but variability increases o Disruptive selection  Extreme phenotypes have higher relative fitness then intermediate phenotypes  Mean phenotype may not change, but variability is increased  May lead to polymorphism o Sexual selection  Selection based on sexes  Cause of sexual dimorphism – the difference in size or appearance between males and females  Intersexual selection  Selection based on interaction between males and females  Males produce otherwise useless structure to impress females  Intrasexual selection  Selection based on interaction between members of the same sex  Males fight for breeding rights to female  Nonrandom mating o Mating according to genotypes o Inbreeding  Genetically related individuals mate with each other  Self fertilization in plants and few animals  Increase frequency of homozygous genotypes and decreases the frequency of heterozygotes 4 BIOLOGY APRIL EXAM REVIEW NOTES 5 17.4 – Maintaining Genetic and Phenotypic Variation  Diploidy reduces effectiveness of natural selection in eliminating harmful recessive alleles from population  Balanced polymorphism o Two or more phenotypes are maintained in fairly stable proportions over many generations o Heterozygotes have higher relative fitness o Different alleles are favored in different environments o Rarity of phenotype provides advantage  Heterozygote advantage o Heterozygote for a particular locus have higher relative fitness the either homozygote  Frequency dependant selection o Selective advantage enjoyed by a particular phenotype depends on its frequency  Neutral variation hypothesis o Some genetic variations are neither preserved nor eliminated buy natural selection o Selectively neutral  Even if various alleles code for slightly different amino acid sequences in protein, the different forms of the proteins may function equally well 17.5 – Adaptation & Evolutionary Constraints  Adaptive trait o Any product of natural selection that increases the relative fitness of an organism in its environment  Adaption o Accumulation of adaptive traits over time o Constraints of adaptive evolution:  No organism can be perfectly adapted to it environment because environments change over time  Natural selection relies on rare mutations and existing genetic variation, thus historically, adaptations take a long time because they must happen in sets of small modifications Chapter 18 – Species 18.2 – Definition of Species  Biological species concept o Group of organisms that can successfully interbreed and produce fertile offspring  Phylogenetic species concept o Group of organisms bound by a unique ancestry  Ecological species concept o Group of organisms that share a distinct ecological niche 5 BIOLOGY APRIL EXAM REVIEW NOTES 6  Hybridization o Two species interbreed and produce fertile offspring 18.3 - One Size Does Not Fit All  Morphological species concept o All individuals of a species share measurable characteristics that distinguish them from individuals of other species 18.6 – Geographic Variation  Subspecies o Local variants of a species o Geographically separated populations of species exhibiting phenotypic variations  Ring species o Ring-shaped geographic distribution of species that surrounds uninhabitable terrain o Adjacent populations can exchange genetic material o Gene flow between distant population occurs through intermediate populations  Cline o Pattern of smooth variation along the geographic gradient o Adaption to differences in environment 18.7 – Reproductive Isolation  Reproductive isolating mechanism o Biological characteristic that prevents the gene pools of two species from mixing even when they are sympatric o Sympatric  Occupying the same area at the same time o Prezygote isolating mechanism  Exert effect before production of zygote  Ecological isolation  Species living in the same geographic region live in different habitats  Temporal isolation  Species living in the same habitat mate at different times of the day or different times of the year  Behavioral isolation  Signals used by one species are not recognized by the other  Courtship displays  Mechanical isolation  Differences in structure of copulatory organs prevent successful mating between individuals of different species  Genetic isolation  Incompatibility between the sperm of one species and the egg of another may prevent fertilization 6 BIOLOGY APRIL EXAM REVIEW NOTES 7 o Postzygote isolating mechanism  Operate after zygote formation  Hybrid inviability  Hybrid organisms die as embryos or at early age  Many genes govern complex processes that transform zygote into mature organism  Hybrid sterility  Parent species differ in number or structure of chromosomes and cannot pair properly during meiosis  Zero fitness because there are no offspring  Hybrid breakdown  F1hybrid generation survives but F2hybrid generations exhibit reduced survival or fertility 18.8 – Geography of Speciation  Speciation o Process of species formation o Allopatric speciation  Physical barrier subdivides a large population  Geographic separation separates small population from a species’ main geographic distribution  Because populations experience distinct mutation and different patterns of natural selection and genetic drift, they isolate genetically  When the barrier recedes, the population is now two separate species that do not interbreed in secondary contact  Hybrid zones  During secondary contact, genetic isolation is incomplete and species may interbreed and produce viable, fertile offspring  Reinforcement  Natural selection favors breeding with own population then hybrid population o Parapatric speciation  Speciation arising between adjacent populations  Occurs if hybrid offspring have low relative fitness o Sympatric speciation  Reproductive isolation evolves between distinct subgroups that arise within one population  Change in diet, behavior or chromosome 18.9 - Genetic Mechanisms of Speciation  Genetic changes leading to reproductive isolation between populations  Genetic divergence o Isolated pockets develop in continuous populations  Polyploidy 7 BIOLOGY APRIL EXAM REVIEW NOTES 8 o Individuals with 2n or more sets of homologous chromosomes o Autopolyploidy  Diploid (2n) individual may produce tetraploid (4n) offspring, each with four 4 complete chromosome sets  Error within meiosis or mitosis o Alloploidy  Two closely related species hybridize and form polyploid offspring  Chromosome alteration o Can lead to genetic isolation and speciation Chapter 19 – Evolution & Classification 19.2 – Systemic Biology  Phylogeny o Evolutionary history of a group of organisms o Phylogenetic tree  Formal hypothesis indentifying likely relationships among species  Taxonomy o Identification and naming of species and their placement in classification o Classification  Arrangement of organisms into hierarchical groups that reflect their relatedness 19.3 – The Linnaean System of Classification  Taxonomic hierarchy o Arrangement of organisms into more inclusive categories 1. Family  Group of genera that closely resemble one another 2. Order  Similar families 3. Class  Similar orders 4. Phyla  Similar classes 5. Kingdom  Similar phyla 6. Domain  All life on earth is classified into three domains Archaea, Bacteria and Eukarya o Taxon  Organism included within any category 19.6 – Phylogenetic Inference & Classification  Monophyletic taxa 8 BIOLOGY APRIL EXAM REVIEW NOTES 9 o Taxon derived from a single ancestral species  Polyphyletic taxa o Taxon with separate evolutionary lineages  Paraphyletic taxon o Taxon that includes ancestor but not all of its descendants  Assumption of parsimony o Simplest explanation should be the most accurate  Traditional evolutionary systematics o Linnaeus’s practice of using phenotypic similarities and differences to infer evolutionary relationships Chapter 20 – Darwin, Fossils and Developmental Biology 20.1 – Recognition of Evolutionary Change  Natural Theology o Sought to name and catalogue all of god’s creature  George Cuvier o Catastrophism  Each layer of fossils represented the remains of organisms that had died in a local catastrophe  George-Louis Leclerc count of Buffon o Vestigial structures  Useless body parts  Jean Baptiste de Lamarck o Proposed the first comprehensive theory of biological evolution o “Perfecting principle” caused organisms to become better suited for their environments o Use it or lose it o All species change through time o Changes passed from one generation to next o Change in response to environment o Hypothesized existence of specific mechanisms that caused evolutionary change 20.2 – Changes in Earth  James Hutton o Gradualism  Earth changed slowly over time  Charles Lyell o Uniformitarianism  Geological processes that sculpted Earth’s surface over long periods of time are exactly the same as the processes we observe today 20.3 – Charles Darwin  Charles Darwin o Artificial selection 9 BIOLOGY APRIL EXAM REVIEW NOTES 10  Selectively breeding individuals with favorable characteristics to enhance those traits in future generations o Natural selection  Organisms with favorable traits to survive and reproduce more readily pass on these traits to next generations o Darwin’s Theory  Purely physical rather then spiritual explanations  Evolutionary change occurs in groups of organisms not in individuals  Described evolution as multi step process  Evolution occurs because some organisms function better in particular environments  Descent with modification  Evolutionary alteration and diversification of ancestral species 20.4 – The Fossil Record  Radiometric dating o Dating using isotopes 20.5 – History, Biogeography and Convergent Evolution  Plate tectonics o Earth’s crust is broken into irregular shaped plates of rock that float on it’s semisolid mantle  Continental Drift o Currents in mantle cause plates, and continents imbedded in them, to move  Con
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