A) Serum is the liquid portion formed after blood clotting.
B) Lymph is the link between blood and tissues.
C) The xylem and phloem transport water and food in plants.
D) In insects closed type of circulatory system is seen.
5. An aphid pierces its proboscis into the ……… to get plant juices
( )
A) Xylem B) phloem C) cambium D) vascular bundle
Annexure-I
The rhesus factor
There is another antigen of red blood cells which is present in 85% of the people of
Britain, this is known as the Rhesus factor, as it was first discovered in Rhesus monkeys.
People who have this are said to be Rhesus positive (Rh+). Those who do not have this
factor are termed Rhesus negative (Rh-). Normally they do not carry an antibody to this
factor in their plasma. However, if Rh+ blood is transfused into the blood of a Rh- person,
against Rh-factors will be formed and these are capable of destroying Rh+ red cells. Under
certain circumstances this is a potential hazard for babies.
If a Rh+ man marries a Rh- woman, some of the children are likely to be Rh+. At birth
there is always some mixing of blood between the circulation of mother and baby and this
may occasionally happen during pregnancy. So, if a child is Rh+ some of its blood will leak
into its mother’s circulation and cause antibodies to form in her blood. If the mother has
more children, not all will necessarily be Rh+, but if they are, the amount of antibodies in
her blood often increases with each pregnancy, and in some instances the antibodies in her
blood may pass into the baby’s blood in sufficient quantities to produce very serious anaemia
and even death. Fortunately these cases are not frequent, and when they do occur, the baby
is given a complete transfusion soon after birth so that the baby’s blood is replaced by
blood containing no antibodies to the rhesus factor. It is now possible for this transfusion
to be carrried out before birth. Another recently developed technique is for the mother to
be given an injection shortly after the birth of her first child which prevents the Rh+ cells
from stimulating the production of the harmful antibody.