STD 11 - 7. Structural organisation in animal — NEET STD 11 Science — Question

Cartilaginous joints in humans

Common characteristic of all vertebrates without exception is

Which one of the following statements are correct ?
(i) Neutrophils and monocytes leucocytes are phagocytic cell; basophils are involved in inflammatory reactions; and eosinophils are associated with allergic reaction.
(ii) Lymphocytes are of two major types - B and T forms. They are responsible for immune response of the body.
(iii) Platelets are also called thrombocytes and are cell fragments produced from microkaryocytes. Blood normally contains 1,500,00-3,500,00 platelets mm^-3.
(iv) Person with O blood groups are called as universal donor' and person with AB blood groups are 'universal recipients".
(v) A condition in which Rh-ve mother has successive pregnancy with Rh-ve foetus is called Erythroblastosis foetalis, which can be fatal to foetus due to production of Rh antibodies by mother. This can be avoided by administering antiRh antibodies to the mother immediately after the delivery of first child.
(vi) Fibrins are formed by the conversion of inactive fibrinogens in plasma by the enzyme thrombokinase.
(vii) Prothrombin are converted into thrombins byenzyme complex thrombokinase.
(viii) Calcium ions plays important role in clotting of blood.
(ix) The fluid present in the lymphatic system is called lymph. It help in absorption of proteins by lacteals present in the intestinal villi.
(x) Fishes has 2 chambered heart; amphibians have 3 and mammals have 4 chambered heart.
(xi) Heart is endodermal in origin.
Choose the correct option given below :-

Which of the following is not a function of kidneys

Origin of earth dates back to

Mammals have the ability to produce a concentrated urine. Which statement not match with production of concentrated urine ?
(i) The Henle's loop and vasa recta play a significant role in this.
(ii) Concentration of urine occurs by counter current mechanism.
(iii) The proximity between the Henle's loop and vasa recta, as well as the counter current in them increases osmolarity from cortex to medulla.
(iv) Osmolarity increasing from 300 mOsmol L' in the cortex to about 1200 mOsmol L' in the inner medulla.
(v) Osmolarity gradient from cortex to medulla is mainly caused by NaCl and urea.
(vi) Presence of osmolarity gradient helps in an easy passage of water from the collecting tubule thereby concentrating the filtrate (urine).
(vii) Human kidneys can produce urine nearly four times concentrated than the initial filtrate formed.

Variation in gene frequencies within populations can occur by chance rather than by natural selection. This is referred to as