A population of a lizard species lives in an ecosystem. An increase in rainfall causes a river
to form in the ecosystem, separating members of
the population. The river remains in the
ecosystem for two years. After a long period of
drought, the river dries up, and the lizards live
together again. The diagrams show the change
to the ecosystem.
Ecosystem after river
is formed.

Which statements BEST describe what
happened to the lizards and the effect on
biodiversity?
A. The lizards on either side of the river passed
genetic mutations onto their offspring. Mutations
decrease biodiversity as they remove unique
genotypes from the gene pool.
B. The lizards on either side of the river did not
experience gene flow and became two different
species. An increase in the number of species in
an area increases biodiversity.
C. The lizards on either side of the river adapted
their physical characteristic to their environment.
Adaptations decrease biodiversity as
characteristics of the original population are lost.
D. The lizards on either side of the river maintained
identical gene sequences. Identical gene
sequences increase biodiversity by ensuring
genetic information is passed onto offspring.