ISC Class 12 Biology Solved Question Paper 2009

Long Answer Type

Advertisement
Zigya App

Explain briefly the movement of water from the soil across the root to the xylem vessel.

he upward transport of water from roots to aerial part of the plant is called ascent of sap. This process occurs in plants through xylem tissue. The water absorbed by root hairs passes through the cortex, passage cells and pericycle to enter the tracheary elements of xylem. It takes place either actively through DPD gradient or passively through transpiration pull. Water is lifted up to leaves as a continuous unbroken column in tracheary elements of xylem by virtue of one or more forces like root pressure, cohesion and adhesion of water and transpiration pull acting simultaneously.
234 Views
  • Switch
    • Advertisement

    Explain natural selection on the basis of sickle-cell anaemia.

    244 Views
    Answer

    (a) Define:

    (i) Vestigeal organs

    (ii) Sympatric speciation

    (iii) Mutagens

    (iv) Biogeography

    (b) Archaeopteryx is considered a connecting link between reptiles and birds. Justify the statement by giving two characteristics of each group.

    (c) Give two differences between natural selection and artificial selection.

    266 Views
    Answer
    What is feedback mechanism? Explain with reference to a hormone secreted from the posterior lobe of the pituitary.  
    177 Views
    Answer

    Draw a neat labelled diagram of a transverse section of human ovary.

    1159 Views
    Answer
    Advertisement
    Describe the procedure of tissue culture in plants.
    392 Views
    Answer

    (a) Explain four measures to control population explosion.

    (b) Write the causative agent and main symptoms of the following diseases
    (i) Tuberculosis (ii) Tetanus
    (iii) Hepatitis (iv) Malaria

    (c) Write two differences between benign tumour and malignant tumour.

    257 Views
    Answer

    a) Write four characteristics that have developed during human evolution.

    (b) What are stem cells? Write two applications of stem cell in medical treatment.

    (c) Mention three basic ways to conserve plant resources.

    473 Views
    Answer
    Write the effects of cytokinins on the plant.  
    336 Views
    Answer
    Advertisement