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Evolution
Capacity of organisms to change over time through reproduction.
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Natural Selection
Passage of beneficial genes to future generations while discouraging the passage of harmful genes.
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Lamarck and Evolutionary Adaptations
Point #1: Individual organisms may develop certain traits, by using or disusing body parts, that are in turn passed on to their offspring. Point #2: Inheritance of acquired characteristics (example: the giraffe’s neck). Flaw: Acquired characteristics are NOT inherited, but acquired after birth!
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Two Main Concepts in The Origin of Species
- 1) Contemporary spp arose from a succession of ancestors through descent with modification.
- 2) Natural selection = mechanism for evolution.
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Biogeography
Distribution of species into various habitats (marsupial migration).
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Comparative Anatomy
Comparison of body structures among different species.
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Homology
Similarity in body structures due to common ancestry.
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Vestigial Organs
Remnants of structures that served important functions in organisms’ ancestors
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Comparative Embryology
Comparison of anatomical structures that appear during early development of different organisms.
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Population
Group of organisms of the same species living in the same area at the same time Smallest unit of evolution : Only populations evolve, not individuals
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Population Genetics
Study of the genetic makeup of populations over time.
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Polymorphism
Two or more variations of a phenotypic form present in noticeable numbers.
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Mutations
Random generation of new alleles
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Meiosis
Specifically synapsis, crossing-over, segregation, independent assortment.
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Fertilization
Genes from two unique family lines uniting in the zygote.
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Hardy-Weinberg Principle
Allele frequency – or the relative occurrence of certain traits –remain constant from one generation to the next.
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Hardy-Weinberg Principle Conditions
1. Populations must be extremelylarge. Small populations increase allele fluctuations. 2. No gene flow. Gene flow increases allele fluctuations. 3. No mutations. Mutations modify the gene pool. 4. Random mating. Random mating increases gamete mixing. 5. No natural selection. Natural selection increases allele fluctuations.
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Genetic Drift
Change in the gene pool of small population due to chance.
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Bottleneck Effect
- Situation in which a drastic reduction in population size occurs resulting in a drastic reduction in genetic diversity.
- Example: Cheetahs
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Founder Effect
Establishment of a new population whose gene pool diverges from the parent population.
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Gene Flow
Genetic additions to and/or sub-tractions from a population resulting from the movement of fertile individuals or gametes.
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Fitness
Contribution an individual makes to the gene pool relative to the contributions of other individuals.
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Directional Selection
Natural selection that favors individuals at one end of the phenotypic range.-
Example: black bear size in Europe during the ice ages - increased during glaciation, decreased during warming.
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Disruptive Selection
Natural selection that favors individuals on both extremes of a phenotypic range over intermediates. Example: Black-bellied seedcracker finches of Cameroon - small bills for soft seeds, large bills for hard seeds – intermediate bills ineffective on both seed types.
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Stabilizing Selection
Black-bellied seedcracker finches of Cameroon - small bills for soft seeds, large bills for hard seeds – intermediate bills ineffective on both seed types. Example: Human birth weights – if the newborn is under or overweight, infant mortality increases
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