Evolution

• Variation - There is genetic variation within a population which can be inherited
• Competition - Overproduction of offspring leads to competition for survival
• Adaptation - Individuals with beneficial adaptations are more likely to survive to pass on their genes
• Directional selection - a single phenotype is favored (extreme), causing the allele frequency to continuously shift in one direction
• Stabilizing selection - genetic diversity decreases as the population stabilizes on a particular trait value
• Disruptive selection - selects against the average individual in a population.

  Both extreme phenotype common in the population, very few in the middle (average).
• Artificial selection - the process of selection conducted under human direction
• Sexual selection -  is a type of natural selection in which evolutionary winners outreproduce others of a population because they are better at securing mates.

  Adaptive traits help individuals defeat rivals for mates, or are the most attractive to the opposite sex.
• Genetic Drift - Change in the existing allele frequency in a population due to random sampling of organisms (chance events)

  Can lead to the elimination of an allele from a population by chance
• Founder Effect - Occurs when a small group of individuals breaks off from a larger population to establish a new population

  Founding individuals may not represent the full genetic diversity of the original population
• Gene Flow - Movement of genes into or out of a population

  May be due to migration of individual organisms that reproduce in their new populations, or to the movement of gametes
• Genetic Drift - Population Bottlenecks

  Drastic reduction in population size, and can reduce the population's genetic diversity

  Causes: environmental disaster, the hunting of a species to the point of extinction, or habitat destruction
• Reproductive Isolation - Occurs when a population splits into two groups and the two populations no longer interbreed
• prezygotic (barriers that prevent fertilization)
• postzygotic (barriers that occur after zygote formation such as organisms that die as embryos or those that are born sterile)
• Temporal Isolation - Members of population mate or breed at different times, which prevents contact
• Behavioral Isolation - Difference in behavior (e.g. courtship rituals) prevents mating
• Ecological Isolation - Potential mates live in the same area but never meet because they occupy different habitats
• Mechanical Isolation

  Difference in the size or shape of reproductive parts prevents mating
• Gametic Isolation

  Gametes come in contact but fertilization does not occur, as the sperm cells of a species can't unite with the eggs of a different species
• Hybrid Inviability

  Mating between two individuals creates a hybrid that does not survive past the embryonic stages, or if born alive dies before maturity
• Hybrid Sterility

  Mating between two individuals creates a hybrid that is sterile
• Allopatric Speciation

  Happens when two populations of the same species become isolated from each other due to geographic changes
• Sympatric Speciation

  Happens when two groups of identical species lived in identical geographical areas, they evolve in such a way that they could no longer interbreed
• Geology is the study of life on Earth based on the evidence found on rocks.
• Paleontology is the study of the existence of life through fossils.
• Relative age - is the age when compared with the ages of other rocks
• Law of Superposition - in layers of horizontal sedimentary rock, the oldest layer is on the bottom
• Absolute age - is the calculation of the number of years that have passed since the rock formed
• Radiometric dating - determine how much time has passed since rocks formed by measuring the radioactive decay of isotopes
• Paleontological - Fossil is any preserved remains, impression, or trace of any once-living thing from a past geological age

  Fossils provided the original evidence for evolution
• Absolute dating - uses chemistry to determine how long ago a fossil formed
• Mold fossils - are fossilized impression made in the substrate

  • a negative image of the organism
• Cast fossils - are formed when a mold is filled in
• Trace fossils - are fossil records of biological activity but not the preserved remains of the plant or animal itself
• True form - fossils are fossils of the actual animal or animal part
• Comparative Anatomy - Similarities and differences in the structures of different species
• Homologous Structures - Similar appearance or function of structures

  because they were inherited from a common ancestor
• Analogous Structures - Structures which are same in form or function in different species that have no known common ancestor
• Divergent evolution - refers to the process by which interbreeding species

  diverged into two or more evolutionary groups.