Differentiate between a population and a species, describe speciation by geographic isolation and explain how speciation and extinction affect biodiversity - NSC Life Sciences - Question 4 - 2017 - Paper 2

Speciation occurs when a population of organisms becomes split by a geographical barrier, such as a mountain range or river. These barriers prevent the two populations from interbreeding, which leads to distinct evolutionary paths through natural selection, operating independently in each group. Over time, due to differing environmental conditions, the two populations may become genetically and phenotypically different from each other. If the barrier is removed, individuals from each population may still not be able to interbreed due to accumulated genetic differences, establishing them as separate species.

Speciation generally increases biodiversity, as the formation of new species adds to the variety of life. Conversely, extinction reduces the number of species, leading to a decrease in biodiversity. The balance between these two processes is crucial, as an increase in speciation contributes positively to the richness of ecosystems, while extinction diminishes it.