There are millions of species that inhabit
this planet, and each of those species plays a unique
role. Some species are important disease vectors, some
are keystone members of ecosystems, some are agricultural
pests, some are university students...the list goes
on and on.
It's important to think about species, because they
are the basic unit of study in most areas of biology,
including: evolutionary biology, ecology, virology,
paleontology, genetics, and conservation biology. As
an example, studying the transmission of malaria would
be virtually impossible without knowing which mosquito
species were vectors, which species they prefer to feed
on, and which species of Plasmodium they carry.