Final answer:
The statement is false; the correct term for species division due to geographical barriers is allopatric speciation. Sympatric speciation refers to speciation within the same geographic area, often due to genetic mutations or behavior differences, not physical isolation.
Step-by-step explanation:
The assertion that a geographical barrier such as a river or a mountain leading to species division is called sympatric speciation is false. When a population of a species becomes geographically separated, such as by a river or mountain range, and these now-isolated populations evolve into distinct species over time due to restricted gene flow, this process is referred to as allopatric speciation, not sympatric speciation. In contrast, sympatric speciation occurs without geographic isolation, often through genetic mutations such as polyploidy in plants, or behavioral differences within a single population that lead to reproductive isolation and eventually speciation.
Allopatric speciation can take various forms, like the formation of a new valley due to erosion or seed dispersal across vast oceans to isolated islands. The degree to which geographic separation will lead to speciation depends on the organism's biology and dispersal capabilities. For instance, if flying insects reside in separate valleys, they might continue to interbreed due to their ability to fly across barriers, thus maintaining gene flow. However, if a new lake isolates two rodent populations, gene flow would more likely be halted, significantly increasing the chance of speciation occurring.