It may cause the transmission of AIDS and Hepatitis B.

Withdrawal syndrome.
These are the characteristic and unpleasant manifestations of the body,when regular dose of drugs/alcohol is abruptly discontinued.
Characteristics:
(i) Anxiety        
(ii) Excess sweating      
(iii) Shakiness  
(iv) Nausea.
In some cases withdrawal symptoms can be severe and even life-threatening.

Steps taken by WHO to control AIDS include:
(i) Ensuring use of disposable needles and syringes.
(ii) Checking blood for HIV.
(iii) Free distribution of condoms and advocating safe sex.
(iv) Controlling drug abuse.
(v) Promoting regular check-up for HIV in susceptible cases.

(i) Typhoid,Polio,Amoebiasis.
(ii) Filariasis,Malaria.
(iii) Pneumonia,common cold.

Diseases can be broadly classified as
(i) Infectious diseases,and
(ii) Non-infectious diseases

Factors to achieve good health:
(i) Awareness about diseases and their effects on different body functions.
(ii) Vaccination/immunisation against many infectious diseases.
(iii) Control of vectors.
(iv) Proper disposal of wastws/excreta.
(v) Periodic cleaning and disinfecting of water reservoirs,tanks,etc. to avoid water-borne diseases.
(vi) Consumption of clean food and drinking water.
(vii) Exercise and relaxation.

Each antibody molecule has four polypeptide chains.

Of them,two are small and called light chains (L) and two of them are longer and called heavy chains(H) hence written as  H₂ L₂.

(a) Sporozoite.
(b) Plasmodium picks up the gametocytes along with the blood meal.
 \(\downarrow \)

Gametocytes reach the intestinal cells of mosquito;fertilisation occurs here.
\(\downarrow \)

Zygote develops and produces sporozoites in the intestine.
\(\downarrow \)

Sporozoites escape from the intestine and reach the salivary glands,where they remain stored.
(c) The rupture of RBCs is associated with the release of a chemical called haemozoin,which is responsible for the chill and high fever.  

Since lymph nodes and bone marrow are the organs where origin and/or maturation and proliferation of lymphocytes occur,they are called lymphoid organs.

Lymph nodes serve to trap the microorganisms or other antigens that enter the lymph;the lymphocytes in the lymph are then activated by these foreign molecules/organisms to mount an immune response.

Bone marrow is the primary lymphoid organ where lymphocytes are produced.

1. Life cycle of Plasmodium in human body.
2. When an infected female Anopheles mosquito bites a person,the sporozoites are injected into the body.
3. They reach the liver cells through blood.
4. The parasite reproduces asexually in the liver cells and by the bursting of liver cells,new cells are released into the blood.
5. They enter the red blood cells (RBCs) and reproduce asexually;by bursting the red blood cells,the cells of the parasite release haemozoin,which causes the cycles of fever,chill and shivering.
6. The released parasite cells infect new red blood cells;some continue the asexual reproduction and cause the cycles of fever.
7. Others enter the sexual stage and form gametocytes in the RBCs,which are picked by the Anopheles mosquito, along with the blood meal.

1. Life cycle of Plasmodium in human body.
2. When an infected female Anopheles mosquito bites a person,the sporozoites are injected into the body.
3. They reach the liver cells through blood.
4. The parasite reproduces asexually in the liver cells and by the bursting of liver cells,new cells are released into the blood.
5. They enter the red blood cells (RBCs) and reproduce asexually;by bursting the red blood cells,the cells of the parasite release haemozoin,which causes the cycles of fever,chill and shivering.
6. The released parasite cells infect new red blood cells;some continue the asexual reproduction and cause the cycles of fever.
7. Others enter the sexual stage and form gametocytes in the RBCs,which are picked by the Anopheles mosquito, along with the blood meal.