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Chapter 4

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Barbara Murck

Chapter 4- Evolution, Biodiversity & Population Ecology Evolution- change over time Natural Selection- the process by which traits that enhance survival and reproduction are passed on more frequently to future generations that those that do not Adaptive trait- a trait that promotes success Mutations- accidental changes in DNA due to additions, deletions, substitutions and frameshift of codons Directional Selection-drives towards on extreme Stabilizing Selection- produces intermediate traits Disruptive Selection- traits diverge from their starting conditions to two distinct traits Divergent Evolution: related species diverge into new species due to selective pressures Convergent Evolution: unrelated species accumulate similar traits due to adapting to selective pressure in similar environments Biodiversity: refers to the total variety of all organisms in an area, taking into account the diversity of species, their genes, their populations, their habitats and their communities A species is a particular type of organism of a population or group of populations whose members share certain characteristics and can freely breed with one another and produce fertile offspring A population is a group of individuals of a species that live in the same area Allopatric speciation: species formation due to physical separation of populations Sympatric speciation: populations become reproductively isolated within the same area. Populations become reproductively isolated occupying a new niche in the same geographic area Fossil Record Fossil: an imprint in stone of dead organisms  as organisms die, some are buried by sediment  the hard parts of their bodies (mostly bones, shells and teeth and sometimes feather and skin) may be preserved as the sediment is compressed into rock  minerals replace the organic material, leaving behind a fossil The fossil record shows us that:  life has existed on Earth for at least 3.5 by  earlier types of organisms evolved into later ones  the number of species existing at any one time has generally increased through time  the species living today are tiny fractions of all species that have ever live  there have been several periods of mass extinctions Extinction: the disappearance of species form Earth Background extinction is the lower, average rate of extinction, representing the normal loss of some species that always occurs. Background extinctions typically occur when normal environmental change, emerging diseases, or competition reduces certain populations to zero. Mass extinctions result from
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