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Showing posts with the label EVOLUTION

Reproductive Structures of Pteridophyte

  Reproductive Structures of Pteridophyte The Pteridophyte sporophyte, besides being a prominent component of soil and vegetation, is an important ornamental plant in gardens and lawns. Indoors, its gracefulness and shape fit it ideally as a plant for pot culture in hallways and living rooms, especially during the months of November to March. Transportation of whole plants from one place to another without damage is attempted by packing them in sand, decomposed silt, ashes, or sawdust. Despite their rich horticultural value, many Pteridophytes are vanishing from nature due to indiscriminate destruction of their natural habitats and capturing of species for ornamental purposes. The best means of conservation is an adequate botanical knowledge of these plants, together with their habitats. The approaches of the non-destructive collection of herbarium specimens are now being stressed. The collection is also supplemented with data regarding the locality and habitat, so as to make it de...

Isolating mechanisms" available in nature.

Discuss the different “isolating mechanisms" available in nature. The development of differentiation in sympatric populations which are  those inhabit the geographical area, will not interbreed even when kept  together. Such a situation results due to varied factors which are collectively  caused isolating mechanisms. Isolating Mechanisms :  The isolating mechanisms may be purely spatial  or may involve specific mechanisms covering reproductive isolation, which  will operate in sympatric population. Setbbins in his recent book, Processes  of Organic Evolution, classified reproductive isolation mechanisms into two  types: (a) Prezygotic mechanisms :   These prevent contact between species at  the time of active reproductive period or else the fertilization is checked even  if pollination may be effectively brought about. These may be:  (1) Spatial or  ecological isolation,  (2) Seasonal or temporal isolation,  (3)...