12th Class Biology Sample Paper Biology - Sample Paper-15

  • question_answer
    Give a detail account of evolution in plants and animals.
     Write short notes on the following:
    (i) Bioinformatics           
    (ii) VNTRs
    (iii) Autoradiography                   
    (iv) Splicing
    (v) Capping


    Evolution in Plants
    The first organisms that existed on land, were plants that occurred before animals. A rough sketch of evolution of plants is discussed below
    (i) Bryophytes were the first plants to colonise lands and were evolved before the vascular plants like pteridophytes and gymnosperms.
    (ii) Vascular plants first originated in Silurian period.
    (iii) Existence of sea weeds and few plants was reported around 320 mya.
    (iv) Herbaceous lycopods and arborescent lycopods evolved form Zosterophyllum of Palaeozoic era.
    (v) Psilophyton  is the common ancestor for horsetails, ferns and gymnosperms.
    Evolution of Animals
    There were plenty of plants when animals came to land.
    (i) Evolution of animals occurred around 500 mya and first animals were invertebrates.
    (ii) Jawless fish and amphibious fish with stout and strong fins originated around 350 mya.
    (iii) The first amphibians and ancestors of modern day frogs were lobefins (Coelacanth).
    (iv) The amphibians evolved into reptiles. They lay thick shelled eggs and have turtles, tortoises and crocodiles as modern descendants.
    (v) The Jurassic period is called as age of reptiles.
    (vi) Reptiles dominated the earth around 200 mya.
    (vii) The first mammals were like shrews and appeared in Triassic period.
    (i) Bioinformatics is the application or computer science and information technology in the biology and medicine field to process information, analyse data and to create new knowledge.
    (ii) VNTRs are short nucleotide repeats in the DNA. They are very specific in each individual and vary in number form person to person, but are inherited. These are Variable Number of Tandem Repeats (VNTRs). (iii) Autoradiography An X-ray film is exposed to the nylon membrane to mark the places where the radipactive DNA probed have bound to the DNA fragments. These places are marked as dark bands when X-ray film is developed. This is known as autoradiography.
    (iv) Splicing the primary transcript contains both the exons (functional) and introns (non-functional). Therefore, they undergo a process called splicing to remove the introns and to join the exons in a proper order.
    (v) Capping the hnRNA undergoes two additional processes. One of them is capping in which methyl guanosine triphosphate, an unusual nucleotide is added to the 5? end of hnRNA.


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