12 public questions tagged with this topic.
Vestigial gill slits in human embryos suggest common ancestry with aquatic organisms like fishes.
Ref: NCERT Class 12 Biology Chapter 6: Evolution Evidences of Evolution - Paleontological and Comparative Anatomy
Following fertilization, the zygote undergoes cleavage, forming a morula before further development into a blastocyst.
Ref: NCERT Class 12 Biology Chapter 2: Human Reproduction Menstrual Cycle Fertilization Implantation Pregnancy Parturition Lactation
Embryonic genome activation typically begins during the blastocyst stage when the embryo starts transcribing its own genes.
Ref: NCERT Class 12 Biology Chapter 2: Human Reproduction Female Reproductive System and Gametogenesis
The clavicle is the first bone to begin ossification during fetal development.
Ref: NCERT Class 11 Biology Chapter 17: Locomotion and Movement Appendicular Skeleton - Limb Bones
The plumule is the part of the embryo that develops into the shoot system.
Ref: NCERT Class 11 Biology chapter - Morphology of flowering plants
Embryological torsion is hallmark of Class Gastropoda occurring during veliger stage, involving 180 degree counterclockwise rotation of visceral mass, mantle and mantle cavity relative to head-foot, bringing mantle cavity and anus anteriorly above head. Facilitates withdrawal into shell for defense, allows head to emerge first when crawling, but imposes sanitation problem where excreta released near head, partially mitigated by asymmetry loss of one ctenidium. Nervous system becomes figure-eight due to visceral loop twisting. Detorsion occurs secondarily in opisthobranchs and nudibranchs. Bivalves, cephalopods and polyplacophorans never undergo torsion, making it gastropod diagnostic apomorphy.
Ref: Campbell Biology, 12th ed., Chapter 33: Gastropod Torsion; NCERT Class 11, Chapter 4, Gastropoda
Rotational cleavage describes mammalian pattern observed in eutherians where first division meridional, second division rotational with one blastomere dividing meridionally and sibling equatorially producing asymmetry early. Cell cycle slow, divisions not synchronous, compaction at eight-cell stage forms morula, differentiation into trophoblast outer and inner cell mass destined to embryo proper. Annelids and molluscs show spiral cleavage, echinoderms radial, roundworms also rotational variant but classic example remains mammals including humans, thus among options mammals exemplify rotational cleavage trait. This concept holds high importance for NEET, CBSE board, CUET and competitive examinations focusing on comparative morphology and
Ref: Gilbert Developmental Biology 11th ed. Mammalian Development; Campbell Biology 12th ed. Chapter 47 Cleavage Types
Radial cleavage pattern features blastomeres aligned directly above one another, mitotic spindles parallel or perpendicular to embryonic polar axis producing symmetrical tiered arrangement with blastomeres contacting one over other. Typical of deuterostomes such as sea urchins, starfish and chordates, it coincides with indeterminate development where isolated blastomere retains capacity forming complete embryo demonstrating regulative ability. Spiral cleavage characterizes protostomes showing oblique spindles and determinate fate. Radial cleavage therefore indicates deuterostome embryology and evolutionary link to regulative development enabling twin formation.
Ref: Campbell Biology 12th ed. Chapter 47 Early Development; Brusca & Brusca Invertebrates Cleavage Pattern
Deuterostomes encompassing Echinodermata, Hemichordata and Chordata display distinctive deuterostomy where blastopore generated by gastrulation invagination persists as anus while mouth perforates secondarily anteriorly from archenteron tip, hence name mouth second. This program associates with radial indeterminate cleavage supporting regulative development where early blastomeres remain totipotent, enterocoelous coelom formation via archenteral pouches and dorsal hollow nerve cord in chordates. Protostomes show opposite blastopore forming mouth, spiral cleavage and schizocoely, making blastopore-to-anus fate primary deuterostome diagnostic criterion. This concept holds high importance for NEET, CBSE board, CUET and competitive examinations focusing on comparative morphology and evolutionary taxonomy within animal and fungal diversity.
Ref: NCERT Class 11 Chapter 4 Deuterostomia; Campbell Biology 12th ed. Chapter 32 Deuterostome Development
Protostomes constitute major bilaterian division including Lophotrochozoa and Ecdysozoa characterized embryologically by spiral determinate cleavage involving oblique spindles producing quartets of smaller micromeres spirally arranged over larger macromeres, cell fate determined early, so isolated blastomere fails to develop fully. Additional hallmarks include blastopore forming mouth first, schizocoelous coelom arising from mesodermal splitting and ventral nerve cord. Radial cleavage, enterocoelom and blastopore forming anus typify deuterostomes instead of protostomes. This concept holds high importance for NEET, CBSE board, CUET and competitive examinations focusing on comparative morphology and evolutionary taxonomy within animal and fungal diversity.
Ref: Campbell Biology 12th ed. Chapter 32 Protostome Synapomorphies; NCERT Class 11 Chapter 4 Cleavage Types
Enterocoelom originates through evagination of archenteron wall during deuterostome gastrulation, where epithelial pouches bulge dorsolaterally, constrict and pinch off as independent coelomic sacs lined by mesoderm. Classic examples include echinoderm tripartite coelom forming protocoel, mesocoel, metacoel and chordate somites and lateral plate from archenteral roof. Contrasts with schizocoelom where solid mesoderm splits. Enterocoely correlates with radial indeterminate cleavage, blastopore forming anus and regulative development, providing mechanism explaining mesodermal segmentation and coelomic compartmentalization in deuterostomes. This concept holds high importance for NEET, CBSE board, CUET and competitive examinations focusing on comparative morphology and evolutionary taxonomy within animal and fungal diversity.
Ref: Campbell Biology 12th ed. Chapter 32 Enterocoely; Brusca & Brusca Invertebrates Deuterostome Development
Go with C — Ectoderm. Within Structure and Function of Nervous System, that statement lines up with the standard definition and the usual exam wording you’ll see. In plain terms, Ectoderm is the option that correctly names the structure, process, or principle asked for in Structure and Function of Nervous System. Holding that picture in mind makes Ectoderm feel natural rather than something you only memorise. Link the term to a real body example (organ, tissue, or ion flow) so the idea stays concrete under exam pressure. A short mental diagram helps — start from stimulus or structure, follow the pathway, and stop at the functional result described by Ectoderm.
Ref: Animal physiology is Unit 7 of the CSIR NET Life Science Syllabus, covering core body systems. It accounts for roughly 10% of the total marks in Sections B and C.
