ENWC201 Lecture Notes - Lecture 4: Sympatric Speciation, Allopatric Speciation, Speciation
Lecture 4: ENWC201
• Niche
o The functional role of an organism considered in the environment in which It
lives
• Competitive exclusion theory
o No two organisms can occupy the same niche at the same time in the same place
o The more similar the organisms are, the more intense the competition between
them
o The less fit species will have to evolve into different niche, move to a different
area, or become extinct
• How do organisms adapt to fill a particular niche?
o Natural selection and evolution
o Charles Darwin, Galapagos
o Natural selection
▪ The process that determines which Individuals will pass on their genes to
the next generation
o Evolution
▪ The changes that we see in the genes and characteristics displayed by
successive generations of a population
o The steps of natural selection
▪ 1) individuals within a species shown genetic variation
▪ 2) organisms reproduce many more offspring than are needed to replace
the parents
▪ 3) excess numbers of individuals result in a shortage of resources
▪ 4) individual variation allows some a greater chance of obtaining
resources, and therefore a greater chance of reproducing than others
▪ 5) over time, each generation is subjected to natural selection. The
percentage of individuals showing favorable variations will thus increase
and those having unfavorable variations will decrease
• Natural selection
o Can lead to considerable change in the characteristics of species and kinds of
species present
• Speciation
o The production of a new species from a previously existing species
o Allopatric speciation: separation of a species into two locations and evolves into
two different species (one old and one new)
▪ Have different natural selection pressures that force change in there
genes
o Sympatric speciation: exist in the same area but evolve into several different
species due to competition of niches
• Extinction:
o The loss of an entire species
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