Published on March 20, 2014
Evolution • Evolution is change in gene (allele) frequencies in populations over time.
Species Species: a group of organisms that, under normal circumstances, can breed with each other and have viable, fertile offspring.
Dogs and Wolves = Same Species
Horse x Donkey =
Mule • Mules are a hybrid species. While they have positive features of both parents they are almost always sterile: i.e. they cannot reproduce;
(male) Lion x (female) Tiger
(male) Tiger x (female) Lion
Species, Population and Evolution Important to remember: evolution occurs within populations, NOT individuals.
Breeding Population • Breeding populations are populations within a species that are genetically isolated from each other, typically by geography. • Gene pool = all the genes carried by all the members of such a group.
Gene Frequency • Gene frequency : how frequently a particular gene is found within a given population. • For instance, you could say that 20% (or 30% or 90%) of a population carry a particular gene (allele)
Means of Evolution • Mutation • Natural Selection • Genetic Drift • Gene Flow • Artificial Selection
Mutation and Evolution • Mutations are random changes in genetic material that occur within individuals. • Mutations are what allow for the emergence of new traits within a population.
Natural Selection • Natural selection: certain traits provide an advantage in a particular environment. Individuals with such traits are more likely to pass on their genes to offspring. • Natural selection is sometimes summarized as “the survival of the fittest.”
Genetic Drift Genetic drift represents changes in gene frequencies due to random chance.
Example of Genetic Drift: The Founder’s Effect Original Population = 50% Blue eyes and 50% Brown eyes From this group a small population separate. Coincidentally, there is a high frequency of brown eyes in this group ⇓ New Group = 80% Brown Eyes and 20% Blue Eyes
Gene Flow and Evolution Gene Flow: when new individuals enter a breeding population and add their genes to the gene pool.
Artificial Selection • Artificial Selection represents breeding other organisms in order for them to display particular traits.
Speciation • Speciation refers to the emergence of two or more species from a common ancestor. • Species represent genetically isolated groups because of their inability to breed with each other.
Language exercise • Italian: Pietra • Portuguese: Pedra • Spanish: Piedra • Catalan: Pedra
Language exercise Latin: Petra ⇓ ⇓ ⇓ Italian: Pietra Portuguese Pedra Spanish: Piedra Catalan: Pedra
Common Ancestor • Common ancestor: the ancestor of two or more different species.
Shared derived characteristic • Shared derived characteristic: features shared by two or more taxonomic groups that are derived from a common ancestor.
Evolution of Equines
“Zonkey” (Zebra-Donkey Hybrid)
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