Govt. Exams
Depolarization occurs when voltage-gated Na+ channels open, allowing rapid Na+ influx that reverses membrane potential towards positive values.
Dystrophin protein deficiency causes Duchenne muscular dystrophy, an X-linked recessive disorder affecting muscle structure and function.
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.