6 public questions tagged with this topic.
Conversion of forests into agricultural land and human settlements is the major cause of habitat loss and fragmentation, the leading cause of biodiversity loss.
Ref: NCERT Class 12 Biology Chapter 13: Biodiversity and Conservation Loss of Biodiversity - Causes - Habitat Loss Overexploitation
Phosphorylation adds 80 Da, but under collision-induced dissociation phosphorylated serine and threonine frequently undergo beta-elimination of phosphoric acid H3PO4 with mass 97.9769 Da, rounded to 98 Da loss from precursor or product ions. Observation of peak 98 Da lower than predicted molecular weight signals neutral loss of phosphate, indicating presence of phosphopeptide that lost H3PO4 during fragmentation. This diagnostic loss distinguishes phosphorylated peptides from unmodified counterparts and contrasts with oxidation or deamination shifts. Recognition of -98 Da loss supports phosphosite localization in signal transduction studies and proteomics research widely used.
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.
During low-energy collision-induced dissociation of protonated peptides, proton mobility model dictates that proton migrates along backbone and weakens peptide bonds, producing mainly b and y type ions. Among these, y ions containing C-terminal portion often dominate spectra because N-terminal fragments may further fragment or undergo cyclization. C-terminal lysine or arginine in tryptic peptides strongly sequesters proton, enhancing stability of y ions. While a-ions accompany b ions, x-ions are rare in CID, and c/z ions appear in electron-based dissociation methods, making y-ion series most informative for database searching in proteomics experiments.
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.
Stevenson's rule, also called the even-electron rule for fragmentation pathways, governs charge retention during dissociation of odd-electron molecular ions in mass spectrometry. When a covalent bond cleaves, two fragments form but only one retains the positive charge. Thermodynamic stability decides outcome; the fragment possessing lower ionization energy better stabilizes the charge through resonance or inductive effects. Consequently, the more substituted, conjugated, or heteroatom-containing fragment typically carries the charge and appears with higher abundance. This principle predicts dominant peaks, aids structural elucidation of natural products, and rationalizes why certain cleavages predominate over random placement.
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.
“Species richness” for fragment size directly influences. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Larger islands usually support more habitats and larger populations, lowering extinction risk; less isolated islands receive colonists more readily and may experience rescue effects. These mechanisms also apply to habitat fragments that function as ecological islands. The remaining alternatives—“Species reproduction rates”, “Mutation rates”, “Species lifespan”—refer to different states, processes, or scales and therefore do not express the same causal relationship. At equilibrium, species identities can continue to turn over even when richness is approximately stable. The model predicts a balance of rates, not an absence of colonization or extinction. Linking the wording to measurable consequences for fitness, abundance, or flux gives the conclusion its scientific meaning and prevents a purely mnemonic interpretation. Field observations could test this account by measuring the proposed driver and the demographic or ecosystem response while controlling plausible confounding factors.
Ref: The Theory of Island Biogeography, MacArthur & Wilson, Ch. 2-4
Fragmentation is the mechanical shredding of detritus into smaller particles, commonly by earthworms, termites, millipedes, insect larvae, and other detritivores. Breaking litter increases surface-area-to-volume ratio, exposes internal tissues, mixes organic matter with mineral soil, and spreads microbial propagules. These changes accelerate leaching and extracellular enzyme access, although fragmentation itself does not mineralize carbon or nutrients. Fungal attack and bacterial oxidation are biochemical processes that often precede and follow fragmentation in a tightly coupled decomposition sequence. Microbial enzymes act outside cells, making surface area and molecular accessibility as important as the nominal energy content of the dead material. Carbon and mineral nutrients follow different accounting paths: energy is dissipated, whereas atoms may be retained, exported, or recycled into new biomass. Decomposition rate therefore emerges from interactions among substrate chemistry, decomposer traits, temperature, water, oxygen, and nutrient balance rather than from a single universal control. At ecosystem scale, these reactions regulate soil fertility, atmospheric carbon exchange, detrital food webs, and the residence time of organic matter.
Ref: Fundamentals of Ecology, Odum & Barrett, 5th Ed., Ch. 3
