Patterns of evolution (types of evolution)

May 27, 2018

Evolution is a process by which living things change over time and adapt to the conditions of their environment.
It may be also defined as the gradual development of the characteristics of plants and animals over time.
Everything in this world changes continuously through space and time. Changes relate to plants and animals (living organisms) are studied under ‘organic evolution’.
The life was originated from the chemical evolution on the primitive earth which was later replaced by organic evolution.
It is caused by changes in the gene pool of the population, usually as a result of natural selection.
Evolution may be classified into following types. They are:

1.Adaptive radiation (Divergent evolution)

The evolution of a number of different groups of organisms from a common ancestral group is called adaptive radiation.
A good example of this process is the evolution of the Australian marsupials into species adapted as carnivores, herbivores, burrowers, fliers, etc.

2.Convergent evolution (Convergence)

The process by which unrelated species evolve to resemble each other is called convergent evolution.
In this evolution, organisms with very different ancestors become more alike because they live in the similar habitats.
e.g., the wings of birds and bats and streamlined bodies of whales and fish are the analogous organs.
Analogous organs are similar in function and appearance but not in origin.

3.Parallel evolution (parallelism)

The development of organisms along similar evolutionary paths due to strong selection pressures acting on all of them in the same way is parallel evolution.
e.g., New world and Old world porcupines shows structural resemblances.

4.Progressive evolution

The evolution in which simple forms of organisms develop towards the complex structural and physiological organizations is progressive evolution.
e.g., evolution of multicellular organisms from unicellular organisms.

5.Retrogressive evolution

The evolution in which complex forms of organisms develop towards simpler structural and physiological organizations is called retrogressive organization.
e.g, monocot plants are considered as more advance groups of plants with simple structure and herbaceous habitat.

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