Patterns of Descent Modification
Patterns of Descent Modification
Patterns of Descent Modification
Biological evolution is a powerful and important process. It is a process which, over billions of years,
gradually selects the organisms that are better adapted to their environment to continuously change life
and make all living organisms in our world the way they are today.
Evolution is not a finished event wherein humans are the final product. Rather, it is a continuing process
which has been changing and forming life on Earth for billions of years, and continues to do so for as
long as organisms are born, dying and competing for what they need to survive and reproduce.
Species - Ernst Mayer’s definition: “Species are groups of interbreeding natural populations that are
reproductively isolated from other such groups.”
Speciation - is the evolutionary process by which populations evolve to become distinct species. It is the
process by which new species develop from existing species.
Mode of Speciation
A. Allopatric Speciation
Allopatric speciation or geographic speciation occurs when some members of a population
become geographically separated from the other members thereby preventing gene flow.
B. Sympatric Speciation
occurs when members of a population that initially occupy the same habitat within the same
range diverge into two or more different species.
C. Parapatric Speciation
occurs when the groups that evolved to be separate species are geographic neighbors. Gene
flow occurs but with great distances is reduced.