Govt Exams
A coelom is a true body cavity completely lined by mesoderm-derived tissue (peritoneum). Coelomate organisms include annelids, molluscs, arthropods, echinoderms, and chordates.
The presence of a notochord, pharyngeal slits, and dorsal hollow nerve cord are defining characteristics of the phylum Chordata, even if these features are present only during embryonic stages.
Echinoderms exhibit radial symmetry as adults and possess a unique water vascular system (hydrostatic skeleton) used for locomotion and feeding.
In insects and many arthropods, the head contains sensory organs, the thorax bears locomotory appendages, and the abdomen contains reproductive and digestive organs.
Flatworms are acoelomate (no body cavity), while roundworms are pseudocoelomate (have a pseudocoelom). This is a fundamental distinction between these phyla.
Most arthropods undergo metamorphosis (complete or incomplete). They have exoskeletons, open circulatory systems, and no notochord.
The muscular foot in molluscs like snails and clams is adapted for locomotion (in gastropods) and attachment to substrates (in bivalves).
The diaphragm is a muscular partition found only in mammals that aids in breathing. Other vertebrate classes use different mechanisms for respiration.
Frogs undergo indirect development with distinct larval stages (tadpole), while reptiles and birds show direct development without free-living larval forms.
Amphibians have a three-chambered heart with two atria and one undivided ventricle. Some mixing of oxygenated and deoxygenated blood occurs.