Govt. Exams
Entrance Exams
Reptiles use specialized pigment cells (chromatophores) and iridophores to change color primarily for camouflage and intraspecific communication.
Lungfish possess both lungs and gills, representing a transitional form between fish and tetrapods, illustrating the evolution from aquatic to terrestrial life.
Deuterostomes (including chordates) form coelom through enterocoely (from gut outpockets), while protostomes use schizocoely (splitting of mesoderm).
The evolution of paired limbs from fins (fins → limbs) allowed movement on land. While lungs evolved in fish, limbs were crucial for terrestrial locomotion in amphibians.
Earthworms belong to Annelida and lack notochord, dorsal nerve cord, and gill slits. Lamprey, Amphioxus, and frog tadpoles possess all three chordate characteristics.
The unidirectional airflow system in bird lungs ensures continuous oxygen supply needed for high metabolism. Feathers insulate; hollow bones reduce weight; vision aids hunting.
While both have amniotic eggs, only mammals possess a diaphragm and mammary glands. Mammals have two occipital condyles, and are endothermic.
The notochord arises from the chordamesoderm (axial mesoderm) derived from the primitive streak during early development.
The evolutionary sequence of animal phyla based on fossil records and molecular evidence shows Sponges (Cambrian), followed by Cnidarians, Flatworms, Arthropods, and later Chordates.
Fish gills operate on a countercurrent exchange principle where blood flows opposite to water flow, maximizing oxygen extraction efficiency to about 80-90%.
