CBSE Class 10 Answered

Branched system of evolutionis referred to as cladogenesis. It is the evolutionary change and diversification resulting from the branching off of new taxa from common ancestral lineages. It can occur as a result of adaptive radiation, which is the divergence or splitting of one species into several. This event usually occurs when a few organisms end up in new, often distant areas or when environmental changes cause several extinctions, opening up ecological niches for the survivors.

Ladder system is referred to as anagenesis. This is a pattern of evolution that results in linear descent with no branching or splitting of the population. Here a species gradually changes over time to the extent that it becomes a new species but does not give rise to additional species. A key point is that the entire population is different from the ancestral population such that the ancestral population can be considered extinct.