The largest artery is the aorta and the largest vein is the vena cava.

$(a)$ How many chambers are present in the heart of $(i)$ fish $(ii)$ amphibians? $(b)$ Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?

Why is transpiration important for plants?

List the three kinds of blood vessels of the human circulatory system and write their functions in tabular form.

Choose the correct statement that describes arteries.

$(a)$ What happens to the heart when muscles work harder?
$(b)$ Which body system is directly affected when a person has heart disease?
$(c)$ Which cells increase in number during infection?