Plant Kingdom Test - 2

Chemotaxonomy is based upon the characteristics of various chemical constituents of organisms. Chemical constituents of plant species have been found to be unvarying and do not change easily. Chemical characters have also helped in establishing relationships and statistical evaluation of taxonomic information.

Artificial systems of classification were based upon morphological characters (such as habit, habitat, colour, number and shape of leaves, etc.) for grouping of organisms, They were mainly based on vegetative characters or on the androecium structure. These systems separated the closely related species since they were based only on a few characteristics. This was not acceptable because vegetative characters are more easily affected by environment

Natural system of classification takes into consideration comparable study of number of characters so as to bring out natural similarities and dissimilarities and hence natural relationships among the organisms. They include morphological characters, anatomical characters, cytological characters, physiology, ontogeny or development, reproduction, cytochemistry and biochemistry, experimental taxonomy, etc.

• Artificial system of classification, put forward by Linnaeus uses one or two morphological characters for grouping of organisms.
• Natural system of classification takes into consideration comparable study of a number of characters so as to bring out natural similarities and dissimilarities and hence natural relationship among the organisms. A natural system for classification of seed Plants was proposed by Bentham add Hooker (1862-1883) in their three-volume treatise 'Genera Plantarum.
• Classification based on evolutionary relationships of organisms is called phylogenetic system of classification. First phylogenetic system was proposed by Engler and Parental (1887-99). In their treatise 'Die Naturlichen famillen' Engler and Prantl arranged flowering plants according to increasing complexity of their floral morphology.

Tracheophyta are those plants which possess conducting or vascular tissues, xylem and phloem. Xylem transports water and minerals while phloem conducts organic food. Tracheophytes include pteridophytes, gymnosperms and angiosperms.

Cryptogame refers to plants without seeds and Phanerogamae refers to plants with seeds. Algae and bryophytes are non-vascular cryptogams. Pteridophytes are vascular cryptogams. Gymnosperms and angiosperms are phanerogams.

Phenetics is a system of classification based on similarity between organisms without regard to their evolutionary relationships. In this type of classification the organisms are arranged according to over all similarity of existing organisms based on observable characters.

The natural system of classification differs from an artificial system in bringing out similarities and dissimilarities. The natural system of classification takes into account a study of a number of characters among the organisms. It brings out natural similarities and dissimilarities between organisms. It takes into consideration the natural relationships among the organisms. It considers characters that are relatively constant.

Numerical taxonomy evaluates resemblances and differences or primitiveness and advancement through statistical methods based on a large number of characters obtained from all disciplines of biology. This is followed by assigning them number and code of computer like plus (+) minus (-) followed by computer analysis.

All species can be defined as either prokaryotes or eukaryotes. Prokaryotes are always single-celled and have no membrane-bound organelles. All bacteria and archaea are prokaryotes. Eukaryotes can be unicellular or multicellular and have membrane-bound organelles, including a nucleus. Protista is a sub-category of eukaryotes that are unicellular.