Evidence of Evolution: Study Notes

For the complete syllabus, check out our PMDC MDCAT Syllabus 2025 article.

EVIDENCE IN FAVOUR OF ORGANIC EVOLUTION

EVIDENCES FROM FOSSIL RECORD (PALEONTOLOGY):

A fossil is any trace of life form the past Fossil record consists of an entire collection of such remains form which paleontologists attempt to reconstruct the biology of the organisms whose remain were left behind.

Example:

Archaeopteryx is a fossil bird had characteristics that show link with reptiles and is a good evidence of evolutionary pathway leading from reptiles to birds.

EVIDENCE FROM CLASSIFICATION (TAXONOMY):

• Taxonomy is a branch of biology in which various organisms showing resemblance have been classified and put into groups and subgroups.
• All the members of phylum chordate have a notochords, nerve cord and gills slits at least at their embryonic stage these resemblance in different groups of chordates like fish amphibians of their common ancestor in the past.

EVIDENCE FROM HOMOLOGY (COMPARATIVE ANATOMY):

The internal general structural plan is same though their external appearance is very different performing different functions such remarkably similar structures performing modified functions in different species are called homologous organs.

Example:

Skeletal system in the wings of bird or bat forelimb of turtle , foreleg of horse, flipper of whale and arm of man are very similar internally having same type of bones and muscles though they all are superficially different form each other and perform different functions in different habitat .

EVIDENCE FORM VESTIGIAL ORGANS (VESTIGES):

Vestiges or vestigial organs are those which have ceased to be of any use to their possessor but they persist in reduced form generation after generation scientists believe these vestiges are retrogressive organs which were well developed and functional in their ancestors.

Example:

• In whales and snakes pelvic bones are present in the reduced form though both have no hind limbs for the attachment with these bones.
• Wings of kiwi and ostrich are reduced and serve no useful function, this proves that these flightless birds have descended from the birds with well-developed wings.
• Splint bones of foot of horse are the remnants of their toes.
• Vestigial organs in man like
• Coccyx is a tail bone or reduced bone which is well developed in other vertebrates
• Vermiform appendix in man is a small finger like reduced caecum. It is a part of digestive tract of many grazing mammals where cellulose is digested by microorganism.
• Nictitating membrane is well developed I in birds to clean their eye ball but in humans it is highly reduced and folded performing no function.
• Ear muscles are well developed in dogs and horses helping them to move their pinna to collect sound waves from different directions in human beings ear muscles are greatly reduced and serve no function.

EVIDENCE FROM EMBRYOLOGY:

Detailed comparative embryological study shows that there are similarities between widely separated animals groups though such animals have markedly different forms and functions

Example: Vertebrate history shows that fishes , salamanders , tortoise , birds , mammals including man had a common ancestors probably some type of primitive fish, so embryonic development of all these animals provides one of the best tools to understand evolutionary linkage among animals .

EVIDENCE FROM BIOCHEMISTRY:

• The blood serum contain specific proteins which determine antigen antibody reaction
• Tests of blood sera have shown the proteins relationship b/w man and apes to old world monkey. The blood proteins of carnivores like cats and dogs are closely related and those of herbivores like goat, cow, sheep and deer resemble mutually.

EVIDENCE FROM DOMESTICATION:

• Domestication means artificial selection in breeding provides evidence for evolution
• Vast diversity has been achieved domestic dogs and pigeons by artificial selective breeding procedure over a short period of time by man. This is evidence that evolution is possible.

Explore our MDCAT webapp for tests, video lectures, and complete prep resources.