Biology Test

Cycas exhibits polyxylic wood formation where successive cambial rings are produced annually in the pericycle or cortex because the first cambial ring is short-lived. This results in multiple wood cylinders being formed over time, unlike monoxylic (single wood cylinder) or pycnoxylic (compact wood with little parenchyma) patterns. Polyxylic wood is characteristic of certain cycads and some other ancient plant lineages.

Gymnosperms typically lack vessels in their xylem tissue, relying primarily on tracheids for water and mineral transport. Tracheids are the fundamental water-conducting cells in gymnosperms, while vessels are a more advanced evolutionary development found predominantly in angiosperms. Xylem fibres and xylem parenchyma are present in gymnosperms as they serve structural and storage functions respectively.

Intraspecific competition refers to competition between individuals of the same population competing for limited resources such as food, territory, or mates. This differs from interspecific competition (between different species) or broader community-level competition. Population regulatory factors like disease or predation might affect populations but are not forms of competition themselves.

Puffs in polytene chromosomes (such as those found in salivary gland chromosomes of Drosophila) are sites of active RNA synthesis, specifically transcriptional activity. These puffs represent regions where the chromatin has decondensed to allow gene expression. They are not sites of DNA duplication or protein synthesis - those processes occur elsewhere in the cell cycle.

Taxon—A group of plants having similar characteristics of any rank is known as taxon.

The movement of water and minerals in a plant involves passage through a root, then in the xylem (especially the vessels) and finally through the leaves.

The cell wall of Nostoc is made up of cellulose and mucopolymer.

Dicot stems possess conjoint, collateral, endarch and open vascular bundles. 'Conjoint' means xylem and phloem are together, 'collateral' means they're on the same radius, 'endarch' describes protoxylem facing inward, and 'open' means cambium is present for secondary growth. Monocot roots and stems have different arrangements - scattered vascular bundles in stems and radial arrangement in roots.

An ecotone is a transition zone between two different ecosystems or vegetational types, such as the edge between a forest and grassland. These areas often have higher species diversity than either adjacent ecosystem because they contain species from both communities plus edge specialists. Ecotones are not specific forest, terrestrial, or xeric-hydrological zones themselves - they are the boundaries between distinct zones.

Passive transport moves substances down their concentration gradient without energy input, while active transport requires metabolic energy (ATP) to move substances against their concentration gradient. This is the fundamental distinction between these two membrane transport mechanisms.

The hexose monophosphate shunt (HMP shunt) is alternatively known as the phosphogluconate pathway or pentose phosphate pathway. It's a metabolic pathway parallel to glycolysis that generates NADPH and pentose sugars.

The absorption spectrum of chlorophyll is useful in identifying the green colour pigment of chlorophyll. It approximates the action spectrum of photosynthesis. It also shows that some colours of light are absorbed more than others

Zeatin is a cytokinin-like substance isolated and crystallized by Letham (1964) from milky endosperm of corn (Zea mays). He named this substance as zeatin.

The matching is: etaerio of berries (custard apple), caryopsis (maize), sorosis (pineapple), drupe (walnut). This tests knowledge of fruit types where etaerio is an aggregate fruit, caryopsis is a single-seeded dry fruit, sorosis is a multiple fruit, and drpe has a hard endocarp.

Prophylactic measures prevent disease by blocking pathogen contact, unlike chemotherapy (treating existing disease), immunization (building immunity), or therapeutic measures (treating after infection). Prophylaxis is prevention-focused.

Crystals of some minerals are found as excretory products of plants. These crystals are made up of calcium oxalate and are found in storage tissues, e.g., pith and cortex. They may be rodlike, prismatic, pyramidal, rhomboidal or needle-like. The needlelike crystals are called raphides.

Ergotism (ergot of rye) is caused by a fungus, Claviceps purpurea.

Biofertilizers are biological materials that improve soil fertility through microorganisms like nitrogen-fixing bacteria, mycorrhizal fungi, or cyanobacteria. Unlike chemical fertilizers, they enhance soil health naturally.

Spontaneous movements occur autonomously without external stimuli, driven by internal plant factors (like turgor pressure changes). Tropic movements are directional responses to stimuli, seismonastic movements respond to touch/shock, and induced movements require external triggers.

Order cycadofilicales of gymnosperms include only fossils. Plants of order cycadofilicales showed some characters of ferns and other characters of gymnosperms, e.g., Medullosa.

Pteridophytes (ferns and their relatives) reproduce via spores, have vascular tissue (xylem and phloem), but lack flowers and seeds. Thallophyta lack vascular tissue, bryophyta lack vascular tissue, and gymnosperms have seeds.

In some plants the stem that twins around the support is hard and woody, such plants are called lianas, e .g ., Tinospora, Hiptage etc.

Berry is one-or many-seeded fleshy fruit. It develops usually from a multicarpellary, syncarpous and superior or inferior ovary with axile or parietal placentation.

Competition is most severe between closely related species occupying the same niche because they have similar resource requirements and directly compete for identical resources. This follows the competitive exclusion principle.