•The morphological species concept is classifying organisms based on their
•Speciation is the process by which one species splits into two or more daughter
species, which thereafter evolve as distinct lineages.
•Reproductive isolation is when individuals in a population can mate with each other
but not with those of another population.
•Biological species concept states that species are groups of actually or potentially
interbreeding natural populations which are reproductively isolated from other
•Not all evolutionary change results in new species; however, if a species becomes
isolated into two different populations. These two populations over a certain amount
of time will encounter a change in allele and genotype frequencies as a result of
evolutionary mechanisms and then the 2 populations may no longer be able to
•Speciation requires gene flow within a population that has formally exchanged genes
to be interrupted.
•Allopatric speciation is when a population is divided by a physical barrier. It can
occur via a Vicariant event in which no individuals disperse and they are separated
by a physical barrier, or via Dispersal which is when a few individuals somehow
cross the physical barrier and then 2 different populations evolve
•Sympatric speciation does not require physical separation however uses ecological
isolation (different resources or different riches). Sympatric speciation usually occurs
by polyploidy which is the duplication of whole set of chromosomes.
•Chromosome duplication in a single species is called autopolyploidy
•Allopolyploidy is the combining of chromosomes from two species and can arise if two
closely related species mate or hybridize. Allopolyploids are often fertile.
•Prezygotic reproductive barriers operate before fertilization occurs
•Habitat isolation is when individuals of different species select different habitats
and therefore never come in contact
•Temporal isolation : If the mating periods of two species do not overlap they will be
reproductively isolated by time