Prepare for NEET Biology Animal Kingdom with MCQs & PYQs on NEET.GUIDE. Access free practice, previous year questions, and expert help to classify and understand animal diversity.
In some Porifera, archaeocytes are totipotent. If an experiment selectively destroyed all archaeocytes within a sponge, which of the following would be the MOST immediate and devastating consequence?
Cessation of water flow through the canal system
Inability to capture food particles
Breakdown of the spongin skeletal structure
Loss of regenerative capacity and inability to differentiate into other cell types
Leucosolenia and Sycon both belong to the Calcarea class. What is a key skeletal difference that distinguishes these two genera?
Leucosolenia lacks spicules, while Sycon possesses them.
Leucosolenia has a siliceous skeleton, while Sycon has a calcareous skeleton.
Leucosolenia has only asconoid organization, while Sycon exhibits syconoid organization.
Leucosolenia reproduces sexually, while Sycon reproduces asexually.
Which of these features is NOT characteristic of the class Hexactinellida?
Six-rayed siliceous spicules
Syncytial body structure with trabecular reticulum
Predominantly found in shallow, warm waters
Often exhibit radial symmetry
The unique 'dermal membrane' observed in some homoscleromorph sponges is primarily composed of which cell type?
Choanocytes
Archaeocytes
Sclerocytes
Pinacocytes
Explain the evolutionary significance of the presence of cellular layers in Porifera despite their lack of true tissues. How does this relate to the potential for more complex body plans in other animal phyla?
The cellular layers in Porifera are analogous to plant tissues, suggesting a common ancestor.
The lack of true tissues limits their complexity, preventing further evolutionary development.
The cellular layers are simply an artifact of their aquatic environment and have no evolutionary significance.
The distinct cell layers, though not forming true tissues, represent a step towards tissue-level organization, foreshadowing the more complex tissue development observed in Eumetazoa.
Which specific cellular mechanism in cnidarians allows for the rapid discharge of nematocysts, considering the internal osmotic pressure is significantly higher than the surrounding seawater?
Passive diffusion of water into the cnidocyte, increasing internal pressure
Active transport of sodium ions out of the cnidocyte, creating an osmotic gradient
Rapid influx of calcium ions triggering forceful contraction of surrounding myoneme cells
Enzymatic breakdown of the cnidocil cap, releasing stored elastic energy
In certain Cnidarians, the medusa stage is absent. This phenomenon is MOST directly related to which ecological adaptation?
Deep-sea environments
Symbiotic relationships with algae
Predation on large, mobile prey
Sessile or benthic lifestyle
The complex interplay of nerve net, cnidocytes, and myoneme cells in Cnidaria is PRIMARILY crucial for which of the following functions?
Regeneration and asexual reproduction
Maintaining osmotic balance
Capturing prey and defense
Symbiotic relationships with other organisms
Coral bleaching, a significant threat to coral reefs, is PRIMARILY caused by the expulsion of which symbiotic organisms due to environmental stress?
Dinoflagellates
Zooxanthellae
Diatoms
Cyanobacteria
Which characteristic distinguishes Cnidarians from Ctenophores, despite both phyla exhibiting radial symmetry and a gelatinous body form?
Presence of a complete digestive system
Presence of cnidocytes (stinging cells)
Bioluminescence capability
Use of colloblasts for prey capture
