Question

Fossil 'X' can be considered to have formed earlier than fossil 'Y' if fossil

• A. ‘Y' is obtained from North America and fossil 'X’ is obtained from South America
• B. 'Y' is found to be structurally more complex than fossil 'X'
• C. 'X' is in a better state of preservation than fossil 'Y'
• D. 'X' is found in a lower stratum of undisturbed sedimentary rocks than fossil 'Y'

Answer 1

The correct option is D 'X' is found in a lower stratum of undisturbed sedimentary rocks than fossil 'Y'

The study of fossils comes under the branch of science called paleontology. Fossils are the preserved remains or impressions of organisms that lived in a past geological age. These include the whole body of the extinct organism, inorganic remains of plants and animals, remains of bones or even moulds, casts and footprints embedded in stratified rocks.

The excavation of fossils reveals the sedimentary layers which further indicates the geological period in which the organism existed. The deeper the sedimentary layer/strata is, the older the fossil would be. This is because the inner or lower sedimentary layer was formed prior to the upper ones, perhaps many years ago.
Therefore, the fossils found in the inner sedimentary layers are older than those found in the upper sedimentary layers. According to the question, fossil 'X' can be considered to have formed earlier than fossil 'Y' if fossil 'X' is found in a lower stratum of undisturbed sedimentary rocks than fossil 'Y'.

The regions from where the fossils have been obtained cannot serve as an appropriate basis for determining the age of fossils. This is because the different regions and different sediment formation on Earth do not always go hand in hand. Therefore, option a, ‘Y' is obtained from North America and fossil 'X’ is obtained from South America, can not be used to determine the age of fossils.

The statement “Fossil 'X' can be considered to have formed earlier than fossil 'Y' if fossil 'Y' is found to be structurally more complex than fossil 'X’ is not always true”. This is because in some cases the newly evolved organisms can have simpler organisation than the organisms which were existing before. For example, sources have revealed that monocot plants are advanced and yet simpler in organisation than dicots.

The fossils which are newer should be actually in a better condition to be preserved than the ones which are older. This is because more degradation happens in fossils as they grow older. In this case if fossil ‘X’ is formed earlier than fossil ‘Y’, fossil 'Y' should be in a better state of preservation than fossil 'X'. Moreover, the state of preservation of fossils cannot determine the age of fossils because any fossil can be destroyed by physical factors like heat, wind, temperature, water, etc. Hence, the statement 'X' is in a better state of preservation than fossil 'Y' is incorrect with respect to this question.