Darwin's theory of natural selection is based on the assumption that change in living systems occurs gradually over long periods of time through an accumulation of very small changes.
(Darwin's theory of natural selection; is based; on the assumption that change in living systems occurs gradually over long periods of time through an accumulation of very small changes) (change in living systems; occurs gradually; T:over long periods of time)
Darwin's theory of natural selection change in living systems
is based occurs gradually
on the assumption that change in living systems occurs gradually over long periods of time through an accumulation of very small changes
T:over long periods of time