16.1 species are reproductively isolated lineages on the tree of life

species

groups of organisms that share a suite of genetic and morphological attributes and are reproductively isolated from other such groups

speciation

the divergence of biological lineages and the emergence of reproductive isolation between lineages

morphological species concept

a species comprises individuals that look alike and those who don't look alike belong to a different species

limitations morphological

males, females, and juveniles don't always look alike, cryptic species, who look alike but can't breed

reproductive isolation

two groups of organisms can no longer exchange genes

biological species concept

groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups

limitiations biological

asexual organisms, limited to single point in evolutionary time

lineage species concept

The definition of a species as a branch on the tree of life, which has a history that starts at a speciation event and ends either at extinction or at another speciation event.

limitations lineage

at a single point in time, the final outcome of the process may not be clear, difficult to predict who will be fully isolated, who will merge again in the future