• During the voyage of Darwin, he visited the Galapagos island.
• There, he came across different varieties of species. He saw the variations in the modification of beaks of finches.

The reptiles and the aves  belong to the vertebrates. Archaeopteryx  is a connecting link between reptiles and birds as it possesses characteristics of both birds and reptiles. Archaeopteryx  possessed a long tail, teeth in jaws, long neck with cervical vertebrae, all are reptilian characters. Like birds, it had wings and beak. It was warm blooded. 

Vestigial organs are degenerate, non-functional and rudimentary organs correspond to fully developed and functional organs of related organism. Third molar (wisdom teeth), plica semilunaris and pyramidalis muscles are vestigial organs. Epiglottis is not a vestigial organ in man. Epiglottis is the structure that prevents the entry of food into respiratory tract during swallowing in man.

 There are about 100 vestigial organs in human being like rudimentry ear muscles (much developed in have elephant and cow) third molar, coccyx (4-5 coccygeal vertebrae) scalp muscle, vermiform appendix, nictitating membrane, ear pinna muscle is vestigial but ear functional bone in man, olecranon process is related to nervous system.

Vestigial organs are those organs which are non-functional in the possessor but were functional in their ancestors and in related animals. Human beings possess many vestigial organs like nictitating membrane in the eye, vermiform appendix at the end if caecum, coccyx and tail muscles, non-functional muscles of the pinna, wisdom teeth, segmental muscle of abdomen and nipples in males.

The name of Charles Darwin and his famous book The Origin of Species will forever be linked with the Galapagos Islands. Although he was only in the Galapagos for five weeks in 1835, it was the wildlife that he saw there that inspired him to develop his Theory of Evolution.

“Ontogeny recapitulates Phylogeny ” known as “Ontogeny repeats Phylogeny ”  is a heredity theory given by Ernst Haeckel.

Ontogeny   refers to the predecessors or the ancestral genetic characters.

Phylogeny   is the genetic combinations of the future generations.

Hence, the theory means that   The characteristics or traits shown by the future generations are the repeatations or recapitulations of the traits of the ancestry.

Paleontology is the branch of biology that studies the forms of life that existed in former geologic periods, mainly by studying fossils . It is the study of the history of life on earth, as reflected in the fossil record. Fossils are the remains or traces of organisms (plants, animals, fungi, bacteria and other single-celled living things) that lived in the geological past and are preserved in the crust of the earth. 

• It was from the seed-eating finches, many other altered forms of beak arose enabling them to be insect, cactus or fruit eaters.
• This led to the discovery of Adaptive radiation.
• Darwin ’s finches are one of the best examples of this process.

Evolution is the gradual changes occurring over generations after generations, during which different species of plants, animals, birds and insects gradually change some of their physical characteristics. These changes include the different aspects of life like genetic drift, mutation, natural selection, thought and technology.The main factors responsible for the evolutionary changes are certain environmental changes and predation pressures.