There are two contrasting ideas about the pace of evolution. One holds that evolution is gradual - a progression of slow steady change. The other sees it as long periods of inactivity, interspersed with bouts of rapid change. These two diagrams show the essential differences between the two concepts. In each, the progression of evolutionary change is visualized as a rolling wheel. The track left behind is the Evolutionary history of the wheel.
The lower wheel, illustrating the gradualist theory, is made up of many tiny fecets. Each of these represents a single mutation, which in turn produces an adaptation. This wheel rolls gradually and smoothly by the accumulation of these small mutational change.
Bursts of creation rather than spread out through time. Ib other words. This data seems to suggest that the rate of evolution is far from constant and can vary from an almost imperceptible rate to one so fast that it appears from the fossil record to be instantaneous.
Other equally continuous fossil records, however, support a different interpretation. One study has examined the incredibly detailed fossil history of a microscopic protozoan in a group called the foraminifera, which are hard-shelled,single-called organisms that float in the plankton. Their calcareous shells sink to the seabed where they become an important constituent of some marine sedimentary rocks.