DEFINITION OF ORGANIC EVOLUTION
Organic evolution is defined as the sum total of adaptive changes from the pre-existing or old form that have taken place over a long time, resulting in a diversity of forms, structure and functions among organisms.
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The concept behind organic evolution is that all living things came into existence from pre-existing living things and that the various species have arisen by a gradual process of change over a very long period of time. The present-day species have not always existed in the present forms but have arisen from pre-existing ancestors.
EVIDENCE OF EVOLUTION
There is much evidence to show that evolution has taken place. These are:
- FOSSIL RECORD:- A fossil is a part of an impression of a plant or animal that lived a very long time ago. Scientists through the use of species techniques called radio-isotope dating are able to determine the ageing fossil. By arranging the fossils according to their age, from the oldest to the youngest they have been able to show an unmistakable evolutionary trend from very simple life forms to complex ones.
Fossils are normally preserved in sedimentary rocks. Fossils record is also called geological paleontological, archaeological or historical record.
- EVIDENCE FROM GEOGRAPHICAL DISTRIBUTION:- It has been proved that living thing tends to show some variation in form, structures and function in relation to differences in climate. In other words, no two types of the same climate produce the same type of plant and animals that have some resemblance. Organisms of the same climate after several years of isolation.