Govt Exams
Insects characteristically have three body regions (head, thorax, abdomen) and three pairs of legs on the thorax. Other arthropods vary in body segmentation and leg numbers.
The correct taxonomic hierarchy is Kingdom → Phylum → Class → Order → Family → Genus → Species (KPCOFGS).
The unidirectional airflow system in bird lungs ensures continuous oxygen supply needed for high metabolism. Feathers insulate; hollow bones reduce weight; vision aids hunting.
Platyhelminthes (flatworms) are acoelomate with bilateral symmetry and organ systems. Cnidaria lacks bilateral symmetry; Nematoda has pseudocoel; Annelida has true coelom.
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 water vascular system and tube feet are unique to Echinodermata. Despite radial adult symmetry, echinoderms have bilateral larvae, indicating deuterostome origin.
All three adaptations—keratinized skin, shelled eggs, and scales—collectively reduce water loss in reptiles while maintaining respiration and reproduction efficiency.
The notochord and dorsal neural tube are fundamental chordate features appearing first in fish and retained throughout vertebrate evolution.
Axolotl (a salamander) exhibits neoteny, retaining larval characteristics (external gills) throughout its life even after sexual maturity.