41 public questions tagged with this topic.
Aschelminthes (roundworms) have a complete digestive system, unlike Platyhelminthes, which have an incomplete digestive tract. This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.
Ref: NCERT Biology Textbook for Class XI and XII (Zoology section), Chapter: Biology - Zoology portion covering relevant system and function.
Hemichordates have a body divided into three parts: proboscis, collar, and trunk. This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.
Ref: NCERT Biology Textbook for Class XI and XII (Zoology section), Chapter: Animal Kingdom, Topic: Basis of classification and salient features of phyla.
Annelids do not have Malpighian tubules; they use nephridia for excretion. This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.
Ref: NCERT Biology Textbook for Class XI and XII (Zoology section), Chapter: Human Physiology - Digestion, Respiration, Circulation, Neural Control and Chemical Coordination, Topic: Organ system functions and hormonal regulation.
Hemichordates have a stomochord, which is similar in function but not homologous to the notochord. This follows from NCERT principle where relation explains outcome clearly for students.
Ref: NCERT Biology Textbook for Class XI and XII (Zoology section), Chapter: Biology - Zoology portion covering relevant system and function, Topic: Structural organization and physiology.
Annelids move by contracting longitudinal and circular muscles along with the help of setae (bristles) for traction. This follows from latest NCERT 2026-27 principle explaining the concept clearly for NEET students in simple steps as per rationalized syllabus.
Ref: NCERT Biology Textbook - Latest Edition for Academic Session 2026-27 (Zoology section, Rationalized Textbook for Class XI and XII), Chapter: Biology - Zoology portion (Latest NCERT Textbooks for Academic Session 2026-27 - Rationalized Edition for Class XI and XII), Topic: Structural organization, physiology, human health and related concepts as per latest syllabus.
Zona pellucida is mammalian extracellular coat synthesized by oocyte and granulosa cells composed of sulfated glycoproteins forming porous matrix. It is evolutionarily and functionally homologous to vitelline envelope surrounding sea urchin and other invertebrate eggs. Both mediate species-restricted sperm binding, stimulate acrosome reaction, and after fertilization undergo cortical granule-induced modifications causing envelope elevation or hardening establishing block to polyspermy. Vitelline envelope can be distinguished from jelly layer external to it, much as zona distinct from cumulus. Analogy underscores conserved fertilization strategy across phyla, reproductive biology and developmental patterning principles.
Ref: Gilbert, Developmental Biology, 12th ed., Chapter 7: Homology of zona pellucida and vitelline envelope in fertilization.
Mammalian zona pellucida is functionally analogous to vitelline envelope surrounding eggs of sea urchins and other invertebrates. Both are extracellular coats composed of sulfated glycoproteins synthesized during oogenesis, mediate species-specific sperm attachment, induce acrosome reaction, and undergo cortical granule-driven modifications resulting in hardening and fertilization envelope elevation. In mammals zona hardens via ovastacin cleavage of ZP2 and zinc crosslinking; in invertebrates vitelline envelope elevates forming permanent block. Analogy reflects evolutionarily conserved strategy regulating gamete interaction, preventing pathological polyspermy and triploid formation during fertilization events.
Ref: Gilbert, Developmental Biology, 12th ed., Chapter 7: Zona pellucida and vitelline envelope homology in fertilization.
In comparative reproductive biology mammalian zona pellucida is functional homolog of vitelline envelope surrounding eggs of echinoderms, amphibians and other vertebrates. Both are extracellular matrices of sulfated glycoproteins that mediate species-specific sperm binding, induce acrosome reaction, establish block to polyspermy after fertilization-induced modifications. Jelly coat lies outside vitelline envelope in sea urchins providing chemotactic peptides, whereas chorion denotes tough outer layer of insect and fish eggs, micropyle is narrow canal for sperm entry. Thus vitelline envelope is direct evolutionary and structural analogue to mammalian zona, preserving conserved elements like ZP domain proteins for gamete recognition across phyla.
Ref: Gilbert, Developmental Biology, Chapter 8: Zona pellucida as mammalian vitelline envelope homolog in fertilization.
Hydra has a simple network of neurons called a nerve net, which lacks a central control system.
Ref: NCERT Class 11 Biology Chapter 18: Neural Control and Coordination Sensory Organs - Eye - Structure and Physiology of Vision
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
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
