Lecture 4: Evolutionary Processes

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Information about Lecture 4: Evolutionary Processes
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Published on March 20, 2014

Author: bioanthro

Source: slideshare.net

Evolutionary Processes

Human Chromosomes

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

Ligers

(male) Tiger x (female) Lion

Tigon

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.

Horse

Onager

Zebra

Donkey

Hyracotherium fossil

Evolution of Equines

“Zonkey” (Zebra-Donkey Hybrid)

Homologous Structures

Analogous Structures

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