Correct Answer - Option 4 : 1, 2, 3 and 4
The correct answer is 1, 2, 3 and 4.
-
Evidence that the evolution of life forms has indeed taken place on earth has come from many quarters.
- Fossils are remains of hard parts of life-forms found in rocks.
-
Rocks form sediments and a cross-section of the earth's crust indicates the arrangement of sediments one over the other during the long history of the earth.
- Different-aged rock sediments contain fossils of different life-forms who probably died during the formation of the particular sediment.
- A study of fossils in different sedimentary layers indicates the geological period in which they existed.
- The study showed that life-forms varied over time and certain life forms are restricted to certain geological timespans.
-
Embryological support for evolution was also proposed by Ernst Heckel based upon the observation of certain features during the embryonic stage common to all vertebrates that are absent in adults.
- 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.
- However, this proposal was disapproved of a careful study performed by Karl Ernst von Baer.
- He noted that embryos never pass through the adult stages of other animals.
- Homology indicates common ancestry.
- In plants also, the thorn and tendrils of Bougainvillea and Cucurbita represent homology.
-
Homology is based on divergent evolution whereas analogy refers to a situation exactly opposite.
- Wings of butterflies and birds look alike. They are not anatomically similar structures though they perform similar functions.
- Hence, analogous structures are a result of convergent evolution - different structures evolving for the same function and hence having similarities.
-
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.
