Life Science(Biology)

    By 1985 Jonathan Shanklin, a materologist with the British Antarctic Survey, Joe Farman and Brian Gardiner published that CFCs, man made compound used in aerosols and cooling devices , is responsible for the thinning of the ozone layer over the Antarctica's Halley Bay research station.Ozone gas is found in the 10-50 km above the Earth surface (stratosphere) and acting as UV radiation, known as UV-B, absorbing layer, so it is termed as Earth's sunscreen .  Photo courteasy :- NASA    In 1974 Mario Molina and F.Sherry Rowland, the 1995   Noble literature in Chemistry were   reported that CFCs could destroy ozone layer of stratosphere and in 1985 it was confirmed by the British Antarctic Survey.Susan Soloman, a researcher with the US government National Ocenic and Atmospheric Administration, in 1985  explained the main cause of the ozone hole and it was over 20 million sq kilometres.     Ozone depletion might results into ris...

Pentoxylon       Two stem genera (i) Pentoxylon sahnii and Nepanioxylon were discovered from Rajmahal hills, India. Morphology: (1) The stems of P.sahanii were 3 mm to 2 cm in cross section. (2) Rhomboidal leaf scars were present on the stem. (3) Leaves were arranged spirally. Leaves were described as Nipaniophyllum raoi. (4) Leaves simple, petiolate , margin entire, apex obtuse , 7cm long and 1 cm broad with a distinct single mid rib. (5) Reproductive organs were borne on short lateral shoots. Stem anatomy: (1) The stem was polystelic ( with 5 steles). (2) Each style was concentric with own cambium but in older stem secondary wood turned into excentric. (3) External to cambium was primary xylem and primary phloem. (4) Leaf traces were came off from long vascular strands. (5) There were 5 smaller strands alternating with the 5 main strands. (6) The secondary xylem was pycnoxylic - it is a coniferous character. (7) Leaf traces possessed centrifugal and centripe...