TYPES OF EVOLUTION -

Sequential evolution                  :                    Minor changes in the gene pool of a population from one generation to the next, with the result that no new populations are formed, but the descendent population is not genetically identical with its predecessor.

Microevolution                            :           Evolution of subspecies or geographic races.

Macroevolution                           :           Evolution of species and genera.

Megaevolution (Simpson 1953)   :            Evolution of families, order, classes and phylum.

Quantum evolution                     :                    (a) Evolution of higher taxonomic group such as orders and classes (b) Evolutionary processes operating above species level i.e., combination of macro and mega evolutions.

Phyletic evolution                       :                    The directional changes in the average character of a population. This is caused either due to adaptation to a shifting environment or due to increasing specialization for a particualr environment or improved adaptation in a constant environment.

Convergent evolution                  :                    Acquiring similar sets of characteristics in response to the adaptation to a common or similar environment by the individuals of two or more totally unrelated or distantly related groups. As a result, the organism with completely different body organization come to possess superficial resemblance.

Divergent evolution/                    :           Development of different structures from a common ancestral form.

adaptive radiation                                            Examples of adaptive radiation occurred on the isolated continent of Australia, where the diversity of habitats and the absence of competitors sparked an adaptive radiation of marsupials (pouched mammals).

Progressive evolution                 :           Development of complex and specialized structure from simpler forms.

Retrogressive evolution              :           Development of simpler structure from complex forms.

Parallel evolution                       :                     Organisms of different classes can acquire similar characters independently and separately to avail the similar environment. Parallel evolution occurs when genetically related species adapt to similar environmental changes in similar ways.

Co-evolution                               :           In nature, species frequently interact so closely that evolutionary changes in one species may cause evolutionary adjustments in others. This evolutionary interaction between organisms is called co-evolution.