(a) Highlight the role of thymus as a lymphoid organ.
(b) Name the cells that are released from the above mentioned gland. Mention how they help in immunity.

State the role of thymus as a lymphoid organ. Name the cells that are released from it and mention their function.

(a) Name the causative agent of typhoid in humans. (b) Name the test administered to confirm the disease. (c) How does the pathogen gain entry into the human body ? Write the diagnostic symptoms and mention the body organ that gets affected in severe cases.

The following is the illustration of the sequence of ovarian events (a - 1) in a human female. (a) Identify the figure that illustrates ovulation and mention the stage of oogenesis it represents. (b) Name the pituitary hormone that has caused the above mentioned event. (c) Explain the changes that occur in the uterus simultaneously in anticipation (d) Write the differences between 'c and 'h'. (e ) Draw a labelled sketch of the structure of a human ovum prior to fertilization.

Mendeleev predicted the existence of certain elements not known at that time and named two of them as Eka-Silicon and Eka-aluminium (a) Name the elements which have taken the place of these elements (b) Mention the group and the period of these electron in the modern periodic table (c) Classify these elements as metals, non-metals or metalloids (d) How many valence electrons are present in each one of them ?

Study the experimental set given below and answer the following questions : Name the chemical filled in the test tubes. Explain how the above mentioned chemical would interfere with the experiment.

Where do the lymphocytes produced by the lymphoid organ mentioned above migrate and how do they affect immunity?

Name the endocrine gland that produces calcitonin and mention the role played by this hormone.

The diagram given below represents the location and structure of an endocrine gland. Study the same and answer the questions that follow: (i) Name the endocrine gland shown in the diagram. (ii) Name the secretion of the gland which regulates basal metabolism (iii) Name the mineral element required for the synthesis of the above mentioned hormone. (iv) Name the disease caused due to undersecretion of the above mentioned hormone in children. (v) Name the disease caused due to hypersecretion of the above mentioned hormone .