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Biology midterm1.docx

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University of Toronto Mississauga
Fiona Rawle

Biology lecture 2 september 12 Lois Pasteur proved that cells arise from cells and not by spontaneous generation implications: b/c all cells come from preexisting cells, all cells are reltated by common ancestry in a muticellular organism have descended from preexisting cells, connected by common ancestry theory of evolution by natural selection Characteristics of species can be modified from generation to generation Descent with modification (process) evolution is a change in the characteristics of a population over time. It means that species are related to one another 2 conditions for natural selection 1. individuals in the pop vary in the characteristics that are heritable VARIABLE HERITABLE REPRODUCTIVE ADVANTAGE Refers to natural selection which can cause evolution 2. certain versions of these heritable traits help individuals survive better Evolutionary change If certain heritable traits lead to increased success in producing offspring, these traits become more common examples of artificial selection race horses dogs agriculture WEB ACTIVITY adult male rams' mating success depends on horn size and body size rams are hunted for their horns large males w/ long horns are not surviving long enough to reproduce 6 years of age be4 they begin breeding The overall weight and horn length of four year old rams has steadily decreased Genes are removed from that population decrease in the breeding of large males and there is concerrn that decrease in the weight of females may occur affects the whole population Differential Reproductive Success Evolution occurs when heritable variation leads to differential success in reproduction Natural selection affects INDIVIDUALS, but it is the POPULATION that evolves An individual organism can NOT evolve Phylogenetic tree reflects relationships between species Taxonomy is the effort to name and classify organisms taxon - is a named group Carolus Linnaeus established the classification system used today phobic fear iso similar poly many glyco sugar Bio lecture september 17 Lysis - to break hydro - water Basic Atomic Structure Life's molecular diversity is based on the properties of carbon Page 18 in textbook Chemical Bonding Electronegativity non-polar/polar covalent bonds depend on difference in electronegativity leads to partial charges gives water its property O>>N>C~=H Carbon is slightly electronegative compared to hydrogen Important: Page 20 txtbook: Electron sharing continuum Hydrogen bonds Why is water polar? Oxygen has high electronegativity hydrogen has lower electronegativity, you get partial charges Each water molecule can form 4 H bonds Ions and polar molecules are hydrophobic uncharged and non polar compounds are hydrophilic Cohesion - binding between like molecules Results in high surface tension Adhesion - binding between unlike molecules Water expands as it changes from a liquid to a solid This is why ice floats Surface tension - water resis
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