Question

Short/Long answer type questions
How do data from the fossil record support the concept that organisms are related through common descent? Explain.

Answer 1

• Palaeontology, the science of fossils, provides the strongest and direct evidence in support of the theory of organic evolution. Fossils are dead remains of plants and animals preserved in the rocks of the remote past. Fossils are found in the sedimentary or stratified rocks. They were formed from those organisms or fragments of organisms which became entombed (covered) under the sediments before they had a chance to disintegrate completely.
• Fossils are important because they give direct evidence of the type of animals and plants that existed at a certain geological age. These records show that the different groups of organisms arose at different times on earth. For example, among the vertebrates, the oldest fossils are those of the fishes, followed by amphibians and progressively mammals are the latest organisms to appear on earth.
  
• By comparing the fossils of different organisms, it is possible to tell the phylogenetic relationships between organisms. Fossil records also show a gradual increase in complexity of organisms over time. Older (lower) rock strata contain fossils showing simple structures while younger (upper) rock strata contain fossils showing more complex structures. Some fossil records have been used to reconstruct an almost complete evolutionary history of the development of certain organisms. For instance, human fossils show a progressive increase in skull sizes to the present age while evolutionary stages of the horse have been reconstructed on the basis of increased complexity of fossil limbs.