Biology Questions

The persons with 'O' blood group do not have antigens in the red corpuscles. So that blood will not cause agglutination of corpuscles if mixed with any type of blood. So group 'O' persons are called universal donors.

In flowering plants one sperm nucleus fertilizes the egg and the other sperm nucleus fuses with two other nuclei found within the ovule, thus forming triploid endosperm.

Hence, double fertilization is unique to flowering plants.

The clotting of blood is a chain reaction initiated by the enzyme thrombokinase produced by the platelets. This causes prothrombin to be converted into thrombin in the presence of Ca++ion.

Thrombin combines with fibrinogen  to produce fibrin threads which entangles the corpuscles to form the clot.

We know that, the nucleotide in DNA is of the form deoxyribose + phosphate group + polymerase.

Hence, Deoxyribose + Phosphate Group + Thymine is the only option in that form of nucleotide in DNA.

Capillaries Tiny blood vessels connecting arteries to veins. These blood vessels carry oxygen

and nutrients to individual cells. Capillaries are the smallest blood vessels in the body, and have

walls only one or two cells thick. (Their diameter is 5 to 10 micrometers, or 5 to 10 millionths of

a meter.)

Capillaries connect arterioles and venules, which are the smaller extensions of the larger arteries and veins.

Nutrients are necessary for break down the food and supply energy to the organisms and to carry out essential life functions.

• Important nutrients are Hydrogen, Carbon and Oxygen.

• Some more important nutrients for plants are : Potassium, Sulphur, Nitrogen, Phosphorous, Calcium and Magnesium.