8 public questions tagged with this topic.
Aquatic arthropods and mollusks use branchial respiration, where gaseous exchange occurs through gills.
Ref: NCERT Class 11 Biology Chapter 14: Breathing and Exchange of Gases Respiratory Organs and Human Respiratory System
Molluscs have a body covered by a calcareous shell and a mantle that secretes the shell.
Ref: NCERT Class 11 Biology Chapter 4: Animal Kingdom Phylum Hemichordata and Chordata - Protochordata
Octopus belongs to phylum Mollusca and is a member of class Cephalopoda.
Ref: NCERT Class 11 Biology Chapter 4: Animal Kingdom Phylum Mollusca and Echinodermata
Mollusks use their muscular foot for movement, which varies in structure depending on the species.
Ref: NCERT Class 11 Biology Chapter 4: Animal Kingdom Phylum Mollusca and Echinodermata
Mollusks have an open circulatory system, except for cephalopods like squids and octopuses, which have a closed circulatory system.
Ref: NCERT Class 11 Biology Chapter 4: Animal Kingdom Phylum Mollusca and Echinodermata
Mollusks have an open circulatory system, but cephalopods (e.g., squids and octopuses) have a closed circulatory system.
Ref: NCERT Class 11 Biology Chapter 4: Animal Kingdom Basis of Classification - Symmetry Coelom Segmentation
Trochophore larva is free-swimming ciliated planktonic prototroch larva characterized by equatorial ciliary band prototroch derived from trochoblasts, apical sensory tuft, ventral stomodaeum, pair protonephridia, serving as developmental link between Annelida and Mollusca. Occurs in primitive marine polychaete annelids and basal molluscan classes including Polyplacophora Bivalvia as early stage preceding veliger. In annelids develops into metatrochophore with added segments, in molluscs metamorphoses into veliger adding foot mantle shell. Presence indicates shared spiralian ancestry within Lophotrochozoa spiral cleavage emphasizing conserved larval morphology and evolutionary kinship between segmented worms and conchiferan molluscs through developmental studies.
Ref: Campbell Biology, 12th ed., Chapter 33: Trochophore larva Annelida Mollusca; NCERT
“Habitat destruction and pollution” for aquatic species, such as mollusks, are most threatened by. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Extinction risk rises when abundance, geographic range, or genetic variation becomes small because demographic chance, environmental fluctuations, inbreeding, and rare catastrophes then have disproportionate effects. Correlated losses among subpopulations further weaken regional persistence. The remaining alternatives—“Parasitism”, “Introduced predators”, “Hunting”—refer to different states, processes, or scales and therefore do not express the same causal relationship. The mechanism should be evaluated across both local and global scales. Local disappearance can be reversed by recolonization, whereas global extinction is irreversible and requires the loss of every surviving population. Field observations could test this account by measuring the proposed driver and the demographic or ecosystem response while controlling plausible confounding factors. This distinction matters because similar surface patterns can arise through different mechanisms, whereas ecological prediction depends on identifying the mechanism that actually changes rates.
Ref: Conservation Biology, Primack & Sher, 6th Ed., Ch. 7
