Evidence for Evolution
The evidence supporting organic evolution is derived from a number of fields of Biology. Those discussed here are:
- Palaeontological evidence: Different-aged rock sediments contain fossils of different life forms that probably died during the formation of the particular sediment. Some of them appear similar to modern organisms. They represent extinct organisms, e.g., Dinosaurs. A study of fossils in different sedimentary layers indicates the geological period in which they existed. Hence, new forms of life have arisen at different times in the history of Earth.
- Embryological evidence: It was proposed by Ernst Heckel based on the observation of certain features during the embryonic stage common to all vertebrates that are absent in adults. For example, the embryos of all vertebrates including humans develop a row of vestigial gill slits just behind the head but it is a functional organ only in fish and not found in any other adult vertebrates.
- Morphological evidence: Though organisms of different species and groups are quite different from each other, they still retain certain common features. Morphological evidence for evolution is derived from:
- Divergent evolution: Species from a common ancestral origin evolve similar anatomical parts (called homologous structures) but with dissimilar functions. For example, whales, bats, cheetahs, and humans (all mammals) share similarities in the pattern of bones of forelimbs.
- Convergent evolution: It creates analogous structures that have similar forms or functions but were not present in the last common ancestor of those groups. Both sharks and dolphins have similar body forms, yet are only distantly related: sharks are fish and dolphins are mammals.
- Molecular evidence: Similarities in proteins and genes performing a given function among diverse organisms give clues to common ancestry. These biochemical similarities point to the same shared ancestry as structural similarities among diverse organisms.
Also Read: Fossils – Tracing Evolutionary Relationships
Evolution Notes for Class 12 Chapter 6
Evolutionary biology is the study of the evolutionary processes that produced the diversity of life on Earth. Earth came into existence sometime between 4 and 5 billion years ago. Life evolved on planet Earth about 3.5 billion years ago. Since then, approximately 15 million different species of organisms have evolved. But only about two million have been identified so far. In this article, we will discuss how the life of these, at first originated on earth and how such a vast variety of organisms evolved through variation and natural selection.
Table of Content
- Origin of Life
- Evolution of Life Forms – A Theory
- Evidence for Evolution
- Adaptive Radiation
- Biological Evolution
- Mechanism of Evolution
- Hardy-Weinberg Principle
- Brief Account of Evolution
- Origin and Evolution of Man
- CBSE Previous Year Question Papers