Life Science(Biology)

 Q1 Define Sustainable Development. Brundtlandt Commission define sustainable development as the development that provides for" ....meeting the need of present generation without compromising the ability of future generation to meet their own needs". Q2 What is "sustainability "? Sustainability refers to a process which can be continued indefinitely without depleting the resource base on which it depends. Therefore, it is the practical goal towards which our interaction with the natural world should be working.

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 centripetal xylem. Rep