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ENV100Y5 (131)
Chapter 4

CHAPTER4.pdf

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Department
Environment
Course
ENV100Y5
Professor
Monika Kwiatkowski
Semester
Summer

Description
Chapter 4 Evolution Biodiversity and Population Ecology Evolution as the Wellspring of Earths BiodiversityEvolution Genetically based change in the appearance functioning andor behaviour of organisms across generations often by the process of natural selection Natural Selection The process by which traits that enhance survival and reproduction are passed on more frequently to future generations of organisms than those that do not thus altering the genetic makeup of populations through time act on genetic variation and is primary driver of evolutionEvolutionary theory is indispensable foundation of modern biology and is important to understand for a full appreciation of environmental scienceNatural Selection Shapes Organisms and DiversityNatural selection is mechanism for evolution and as a way to explain living thingsDarwin and Wallace recognized thatOrganisms produce more offspring than can possible survive and that some offspring may be more likely than others to survive and reproduceWhichever characteristics give certain individuals an advantage in surviving and reproducing might be inherited by their offspringAdaptive TraitAdaptation A trait that confers greater likelihood that an individual will reproduceMaladaptive A trait that reduces successNatural Selection Acts on Genetic VariationFor organism to pass trait along to future generations heritable genes in organisms DNA must code for that traitMutations An accidental change in DNA that may range in magnitude from the deletion substitution or addition of a single nucleotide to a change affecting entire sets of chromosomes provide the raw material for evolutionary change can be deadly or beneficial Recombination Process that produces novel combinations of genes generation variation among individualsNatural selection acts on genetic variation in three ways 1 Directional Selection Selection that drives a feature in one direction rather than another toward larger or smaller or faster or slower 2 Stabilizing Selection Selection produces intermediate traits in essence preserving the status quo 3 Disruptive Selection Trail diverges from its starting condition in two or more directions Selective Pressures from the Environment Influence AdaptationDivergent Evolution The process whereby two species with a common genetic ancestor evolve different traits over time as a result of adaptation to selective pressures from different environmentshabitats characteristics of populations eventually become so different that they are no longer the same species
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