9 public questions tagged with this topic.
Biotic potential is the highest possible reproductive capacity of a species when environmental conditions are optimal.
Ref: NCERT Class 12 Biology Chapter 11: Organisms and Populations Organism and Environment - Major Biomes Abiotic Factors
The cerebrum contains motor areas that control voluntary movements.
Ref: NCERT Class 11 Biology Chapter 18: Neural Control and Coordination Central Nervous System - Brain - Midbrain and Hindbrain
The sigmoid growth curve consists of the lag phase, log phase, and stationary phase, representing plant growth over time.
Ref: NCERT Class 11 Biology Chapter 13: Plant Growth and Development Growth - Phases Differentiation Dedifferentiation Redifferentiation
In animal classification, phylum is placed directly below kingdom. In plants, the corresponding category is called division.
Ref: NCERT Class 11 Biology Chapter 1: The Living World Taxonomic Categories - Family Order Class Phylum Kingdom
In Alstonia, more than two leaves are arranged in a whorl at each node, exhibiting whorled phyllotaxy.
Ref: NCERT Class 11 Biology chapter - Morphology of flowering plants
Phylum Annelida unequivocally diagnosed by true metameric segmentation also called metamerism where body divided linearly into serially repeated similar segments each containing identical sets of coelomic compartments bounded by septa, paired nephridia, ganglia of ventral cord, segmental vessels, musculature derived from teloblastic growth and chaetae. Segmentation permits regional tagmosis, redundancy, flexible locomotion via peristalsis and parapodia. External annulations often correspond to septa though loss occurs in leeches. Differs from pseudosegmentation of tapeworm strobila or arthropod tagmata representing true internal repetition. Annelid segmentation co-occurs with closed circulation and ventral cord consistently observed across polychaetes and oligochaetes.
Ref: NCERT Class 11 Biology, Chapter 4: Annelida metameric segmentation; Campbell Biology 12th ed. Chapter 33
Nemerteans superficially resemble turbellarian flatworms due to dorsoventrally flattened ciliated creeping body, soft unsegmented appearance, but fundamentally distinguished by several evolutionary advances: possession of true complete tubular system with separate anterior mouth and posterior anus allowing continuous unidirectional processing and fecal egestion, compared to incomplete blind branching gastrovascular cavity of Platyhelminthes, plus development of well-organized closed circulatory system with dorsal ventral vessels containing nucleated erythrocytes with hemoglobin absent in flatworms. Additionally possess protonephridial excretory system and unique rhynchocoel containing proboscis elevating them to higher grade approaching coelomates.
Ref: Ruppert et al., Invertebrate Zoology, Chapter 20: Nemertea complete gut closed circulation
Duplicate dominant epistasis occurs when dominant alleles at either of two loci independently encode functionally redundant enzymes producing identical phenotype. Only double homozygous recessive aabb lacks any functional copy and displays alternate trait, while all genotypes carrying at least one dominant allele A or B show common phenotype because either enzyme suffices. This redundancy causes fifteen individuals in F2 to share dominant outcome and one to show recessive, generating exactly two phenotypic classes 15:1. Shepherd's purse capsule or rice awn examples demonstrate interchangeable loci where either gene alone completes same developmental step effectively.
Ref: Griffiths et al., Introduction to Genetic Analysis, 12th ed., Chapter 9: Duplicate Genes 15:1 Two Classes
Complementary gene interaction involves two independently assorting non-allelic loci controlling one trait through sequential biosynthetic pathway where each dominant allele encodes distinct enzyme. Neither allele alone can produce final end product because intermediate from first reaction must be processed by second enzyme. Classic sweet pea flower colour illustrates mechanism: genes C and P convert colourless precursor to purple anthocyanin stepwise requiring both dominant alleles together; any homozygous recessive genotype remains white. This functional cooperation yields characteristic 9:7 ratio in F2 progeny, demonstrating pathway dependence.
Ref: Griffiths et al., Introduction to Genetic Analysis, 12th ed., Chapter 9: Complementary Interaction 9:7 Ratio
