1. The primary effluent in passed into large aeration tank for aerobic digestion of effluent by flocs masses of bacteria associated with fungi in a mesh like structures to decrease its BOD by digesting the organic matter in it.
2. 'Sediment' formed is referred to as activated sludge. A part of this is pumped back into the aeration tank to serve as the inoculum.
3. The final step in the settling tank is anaerobic digestion by fungi and bacteria in anaerobic sludge digesters. After which,the treated effluent is generally released into natural water bodies.
(ii) Rhizobium fixes atmospheric nitrogen into plant usable organic forms by forming symbiotic association with legumes.
Azospirillum fixes atmospheric nitrogen while free living in the soil and enriching the nitrogen content of soil.

The factors necessary to maintain good health are:
(i) Balanced diet
(ii) Clean food and drinking water.
(iii) Personal hygiene.
(iv) Regular exercise/yoga and relaxation.
(v)  Awareness about diseases, their dispersal and effect on our body.
(vi) Vaccination/immunisation against infectious diseases.
(vii) Proper disposal of wastes/excreta.

(a) Leguminous plant and nitrogen-fixing bacteria, e.g., chickpea and Rhizobium of Leguminosae or Fabaceae plants and nitrogen fixing-bacteria
(b) Steps in the formation of root nodules:
(i) Root hair of the leguminous plant curls upon contact with nitrogen fixing bacterium, which secretes chemicals.
(ii) Nitrogen-fixing bacteria proliferate withincurled root hair.
(iii)The plant responds by forming an infection thread of the plasma membrane, which grows inward from the infected cell of the host, separating it from the rest of the plant.
(iv) Cell division is stimulated in the infected tissue and more bacteria invade the newly formed cells, and a nodule is formed. Auxin from leguminous plant cells and cytokinin from bacteria help in this cell division.
Physiological processes : Photosynthesis and respiration provide FAD and ATP for fixation of atmospheric nitrogen.

The process of sewage water treatment before being discharged into natural water bodies.

1. Primary treatment: These treatment steps involve physical removal of particles from the sewage through filtration and sedimentation. These are removed in stages; initially, floating debris is removed by sequential filtration. Then the grit (soil and small pebbles) are removed by sedimentation. All solids that settle form the primary sludge, and the supernatant forms the effluent. The effluent from the primary settling tank is taken for.
2. Secondary treatment: During secondary treatment, the primary effluent is passed into large aeration tanks. Air is also passed into these tanks and agitated. This enables the growth of aerobic microbes into flocs. While growing, the bacteria consume majority of the organic matter present in the effluent. This causes a significant reduction in the biochemical oxygen demand (BOD) of the effluent. Essential to control pollution in natural water bodies, to check water borne diseases/pathogenic organism.

The sewage treatment is essential before water is released into water bodies as sewage present in water causes water pollution and as a consequence, incidence
of water borne diseases increases.

(i) Biogas is a mixture of gases produced from degradable organic matter by activity of microorganisms.
(ii) It is used as a fuel for heating, cooking. lighting, power for irrigation, etc.
(iii) Microorganisms involved are methanogens such as methanobacterium.
(iv) Anukool is helpful, intelligent, has human values and care for people. 

(a) 

(b) The carcinogens are asbestos, gamma rays, tobacco smoke and arsenic.
(c) Detection and diagnosis of cancer depends upon histological features of malignant structure.
(i) Biopsy of bone marrow and abnormal count of WBCs is done in leukemia.
(ii) Pap test (cytological staining) is used for detecting cancer of cervix and other genital tract parts.
(iii) Radiography, CT scan (Computed Tomography), Magnetic Resonance Imaging (MRI scan) are useful technique to detect cancer of internal organs.

(i) Biofertilisers are the microorganisms which bring about soil nutrient enrichment, maximise ecological benefits and minimise environmental hazards.
(ii) Nostoc, Anabaena.
(iii) The scientist was concerned about the clean environment and, therefore, he suggested Rahul to use the ecofriendly technique.

A.fertilisers, pesticides;
B. thuringienss, Cry;
C. pathogens;
D. phosphorus;
E. nodules, leguminous, cyanobacteria;
F. texture;
G.protein, human;
H. low;
 I. methanogens
J. Lactic acid bacteria

(a) (i) Normal cells whow a property celled contact inhibition by virtue of which contact with other cells inhibits their uncontrolled growth.Cancer cells appear to have lost this property and as result continue to divide to give masses of cells called tumours.
(ii) Metastasis: Cancerous cells sloughed off from tumours reach distant sites through blood or other body fluids and start a tumour there.This property is called metastasis.It is the most fearsome property of malignant tumours.
(b) (i) Viral oncogenes 
(ii) Cellular oncogenes (C-onc) or proto-oncogenes when activated under certain conditions, whether could head to oncogenic transfermation of the cells.
(c) Technique like radiography (use of X-rays),CT (Compiled Tomography) and MRI (magnetic Resonance Imaging are useful to detect cancer of internal organs.
(d) \(\alpha \)-interferons are biological response modifiers are given to cancer patients.These substances activate immune system and help in destroy the tumour.

(i) Ascariasis
Cause. It is caused by Ascaris lumbricoides.(round worm).
Symptoms.Its symptoms include:
(a) Blockage of intestinal passage,
(b)Anaemia,
(c)Abdominal/muscular pain,
(d)Internal bleeding,
(e)Nausea and headache.
Modes of transmission. Infection is through contaminated vegetables, fruits and water as eggs of parasite excreted by the infected persons contaminate soil, plants and water
(ii) Filariasis/Elephantiasis
Cause. It is caused by wuchereria bancrofti and wuchereria malayi(filarial worms)
They normally cause inflammation of the organs in which they live for many years.
They normally affect the lymph vessels of the lower limbs (causing them to swell like that of an elephant, hence called elephantiasis).
Genital organs may also be affected leading to gross deformation.
Modes of transmission. The female culex mosquito is the vector.
(iii)Ringworms
Cause. These are caused by fungi like microsporum, Epidermophyton and Trichophyton
Symptoms. The symptoms include
(i) dry scaly lesions on skins, nails and scalp.
(ii)lesions are accompanied by itching.
Modes of transmission. Ringworms are generally acquired from soil or by direct contact with the contaminated articles used by the infected persons.

Pulse Polio Programme was started in 1978.Pulse Polio programme is the administration of oral Polio vaccine at regular intervals to the children under the age of five.Government provides vaccine free of cost.Many NGOs also participate with a mission to make India free of polio disease OPV is the vaccine given orally.The project 'Fight poliomyelitis' through a large cycle vaccination programme and monitoring for polio cases.F Due to this project, on march 27,2014 World Health Organization declared India a polio free country since no cause of wild polio had been reported. 

MOEF of Government of India has initiated the Yamuna Action Plan and Ganga Action plan for saving Yamuna and Ganga rivers respectively.
Ganga Action Plan:
1.Due to increased urbanisation and industrialisation there is a huge quantity of sewage produced; but there are not enough sewage treatments plants and hence the untreated sewage is let into major rivers.
2. The government has planned to build a number of sewage treatment plants, because the sewage and effluents from the areas nearby Ganga rivers can be treated before they are let into the river.
3. The objective of Ganga Action Plan is to save the river from pollution.
Yamuna Action plan :
In order to protect the major rivers of India from sewage pollution, the Ministry of Environment and Forests has initiated development of sewage treatment plants under the National River Conservation Authority, e.g., Ganga Action Plan and Yamuna Action Plan. Industries contribute chemical effluents to the river's pollution load and the toxicity kills aquatic animals in large sections of the river.

Treatment of cancer:
The following methods (one or in combination) can help to treat cancer.
(i) Surgery
The tumour cells are surgically removed to reduce the load of cancerous cell.
(ii) Radiotheraphy
The tumour cells are irradiated wholly (but taking care of the surrounding normal cells) with safe doses of radiations.
(iii) Chemotherapy
Certain drugs are used to kill the cancerous cells,but majority of the drugs have side effects like hair fall,anaemia,etc.
(iv) Immunotherapy
This involves the use of biological response-modifiers,like alpha-interferon,which activate the immune system and help in destroying the tumour.

Asexual Phase
It occurs in the human host. The sporozoites enter the human body through the bite of an infected female Anopheles mosquito.
They reach the liver through blood and multiply within the liver cells.
Such liver cells burst and release the parasite into blood.
The parasite enters RBCs, multiply in them and cause their rupture.
The rupture of RBCs is associated with the release of a toxin, called haemozoin, which is responsible for the chill/shivering and the high temperature (fever) of the body. Sexual Phase
It starts with the formation of gametocytes in the RBCs of man.
The parasite then enters the female Anopheles mosquito, along with the blood when it bites the infected person.
Further development occurs in the stomach wall of mosquito.
The gametes fuse to form a zygote. The zygote undergoes further development to form sporozoites.
Sporozoites are transported to and stored in the salivary glands of the mosquito and are transferred to a human body during the bite of the mosquito.