33 public questions tagged with this topic.
Despite covering 70% of the Earth's surface, oceans have low productivity due to limited nutrient availability in deeper waters.
Ref: NCERT Class 12 Biology Chapter 12: Ecosystem Productivity - Primary Secondary GPP NPP
Marine bony fishes maintain buoyancy using an air bladder, which helps control their depth in water.
Ref: NCERT Class 11 Biology Chapter 4: Animal Kingdom Phylum Mollusca and Echinodermata
The water vascular system in echinoderms helps in locomotion using tube feet and aids in capturing food.
Ref: NCERT Class 11 Biology Chapter 4: Animal Kingdom Phylum Mollusca and Echinodermata
Asterias (starfish) belongs to phylum Echinodermata, which includes marine animals with a water vascular system.
Ref: NCERT Class 11 Biology Chapter 4: Animal Kingdom Phylum Mollusca and Echinodermata
Echinoderms do not have a closed circulatory system; they rely on their water vascular system for circulation.
Ref: NCERT Class 11 Biology Chapter 4: Animal Kingdom Phylum Mollusca and Echinodermata
Most dinoflagellates possess two flagella. One lies longitudinally, while the other lies transversely in a furrow between the stiff cellulose plates of the cell wall.
Ref: NCERT Class 11 Biology Chapter 2: Biological Classification Protista - Chrysophytes and Dinoflagellates
Red dinoflagellates such as Gonyaulax may multiply so rapidly that the sea appears red. Toxins released by these large populations may kill marine animals such as fishes.
Ref: NCERT Class 11 Biology Chapter 2: Biological Classification Protista - Chrysophytes and Dinoflagellates
Dinoflagellates may appear yellow, green, brown, blue or red depending on the principal pigments present in their cells. Most members are marine and photosynthetic.
Ref: NCERT Class 11 Biology Chapter 2: Biological Classification Protista - Chrysophytes and Dinoflagellates
Contrasting with cnidarians possessing blind sac gastrovascular cavity with single opening, ctenophores exhibit through gut considered complete alimentary canal with distinct mouth at oral pole leading to pharynx stomach and canals extending meridionally beneath comb rows distributing nutrients and two aboral anal pores near apical organ expelling residues. Food enters via mouth after capture digested in stomach extracellularly intracellularly via phagocytes circulated through canals. Presence anal pores allows separate egestion enabling unidirectional processing more efficient than cnidarian blind gut considered advanced though debated homology with bilaterian anus and through gut evolution in early metazoans.
Ref: NCERT Class 11 Biology, Chapter 4: Ctenophora complete gut anal pores; Campbell Biology
Ctenophores capture zooplankton prey not through nematocysts like cnidarians but via adhesive cells termed colloblasts located on pair long retractile tentacles present in Tentaculata absent in Nuda such as Beroe which feed by swallowing prey whole. Each colloblast comprises spiral filament coiled around core adhesive granules secreting sticky glue. Upon contact granules release adhesive tethering victim spiral uncoils absorbing energy. Tentacle retracts moving prey toward oral groove. Mechanism distinct from nematocyst piercing reflecting independent evolution planktonic predator capture strategies sticky rather than stinging studied as biological adhesion model for biomimetic applications and marine ecology.
Ref: NCERT Class 11 Biology, Chapter 4: Ctenophora colloblasts; Campbell Biology, Chapter 33
Ctenophora known as comb jellies recognized by eight longitudinal meridional rows of ciliary comb plates called ctenes composed of fused macrocilia stacked as transverse combs beating coordinated metachronal waves for ciliary locomotion through viscous propulsion rather than muscular pulsation. Plates diffract light producing iridescent effect. Each row forms effective paddle. Unique to phylum inspiring name cteno comb and phora bearing. Absent in cnidarians which employ muscular contraction. Some benthic ctenophores secondarily lost combs as adaptation to creeping lifestyle on substrate feeding on small plankton and benthic organisms with reduced swimming ability and altered morphology.
Ref: NCERT Class 11 Biology, Chapter 4: Ctenophora comb plates ctenes; Campbell Biology Chapter 33
Cnidarian body forms include sessile polyp cylindrical with oral disc and pelagic medusa bell-shaped. Dominant medusa stage large free-swimming gelatinous with thick mesoglea prominent gonads within gastrodermis, nerve ring with sensory rhopalia found in Scyphozoa true jellyfishes where scyphomedusa develops from scyphistoma via strobilation producing ephyrae larvae and Cubozoa box jellies with cuboidal bell potent venom. Medusa is primary reproductive adult. Hydrozoa mostly polyp dominant except hydromedusae Anthozoa exclusively polypoid lacking medusa adapting mostly benthic predatory lifestyle with varying coloniality and skeletal deposition in reef environments globally widely distributed and ecologically important as predators and habitat builders.
Ref: Campbell Biology, 12th ed., Chapter 33: Scyphozoa dominant medusa; NCERT Animal Kingdom
