Homologous structures

Homologous structures In vertebrates, comparative anatomical studies reveal a basic plan in various structures such as fore limbs and hind limbs. Fore limbs of vertebrates exhibit anatomical similarity with each other and is made of similar bones such as humerus, radius, ulna, carpals, metacarpals and phalanges. Carpals Phalanges Ulna Radius Humerus Whale Cat Horse Human Bat Bird Fig. .

Forelimbs of terrestrial vertebrates to show homology Structures which are similar in origin but perform different functions are called Evolution include coccyx, wisdom teeth, ear muscles, body hair, mammae in male, nictitating membrane of the eye, etc., Connecting link The organisms which possess the characters of two different groups (transitional stage) are called connecting links. Example Peripatus (connecting link between Annelida and Arthropoda), Archeopteryx (connecting link between Reptiles and Aves). Atavistic organs Sudden appearance of vestigial organs in highly evolved organisms is called atavistic organs. Example, presence of tail in a human baby is an atavistic organ.