(a) Describe the procedure of hybirdisation in plants.

(b) Name the causative agent and the main preventive measure for each of the following diseases:

(i) Amoebiasis
(ii) Rabies

(iii) Pneumonia

(c) What is manure? Explain any two types of manures.


(a) Hybridization is the process of combining different varieties of organisms to create a hybrid. It is the method of producing a new crop in which two or more plants of unlike genetical constitution are crossed together.

Hybridization Procedure : The various steps in hybridization are as follows:

1. Selection of Parents : The first step in hybridization is to select the plants which are to be used as parents and can supply all desired characters.

2. Selfing of parents : This is the second step which involves artificial self-pollination of parents. It is essential for eliminating undersirable characters and obtaining onbreds.

3. Emasculation : Emasculation is the third step in hybridization procedure. The process of removal of stamens from female parent before they have burst and shed their pollens is called emasculation. The main purpose of emasculation is to prevent self-fertilization, that is why stamens are removed before the anthers ripe, dehisce and self-pollinate the stigma. Young flower buds which are yet to open are selected for emasculation.

4. Bagging : This is the fourth step in hybridization. Both male and female flowers are bagged separately to prevent contamination in staminate flowers and cross pollination in pistillate flowers. The bags are made usually of paper, cloth, plastic or cellophane.

5. Crossing : Crossing is the artificial cross-pollination between genetically unlike plants: In this process, viable pollens are collected from desired male parent and transferred to the stigma of desired emasculated female parent. Pollens are collected in petri dishes or paper bags and are immediately brushed or dusted on the stigma of emasculated female flower, which is bagged immediately.

6. Raising F1 generation : In this step, mature seeds of F1 generation are harvested, dried and stored. In the next season, these seeds are sown separately to raise the F1 generation. The plants obtained from F1 generation are called hybrids.

(b) 

Disease Causative agent Preventive measure
Amoebiasis Entamoeba histolytica Maintaining proper hygiene 
Rabies Rabies virus or Rhabhidovirus Vaccinations of animals
Pneumonia Streptococcus pneumoniae Practicing proper hygiene and getting immunised


(c) Manures are the organic substances obtained by the decomposition of animal wastes and plant residues which supply essential elements and humus to the soil. They are added mainly to improve the physical conditions of the soil, to replenish and keep up its humus status, to maintain optimum conditions for the activities of soil micro organism. They help to supply all the elements of fertility which crops require in adequate proportions.

Types of manures :-

(i) Composted Manures : Composting is the process of vegetable and animal refuse to a quickly utilizable condition for improving and maintaining soil fertility.

(ii) Farmyard Manures : Good quality Farmyard manures is however the most valuable organic matter for the soil. . It consists of a mixture of cattle dung, the bedding used in the stable and remnants of straw and plant stalks fed to cattle. Partially rotten manures are generally applied to the soil.

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What is manure ? Explain any two types of manures. 

Manure is a content that increases the soil fertility. Two types of manure are—green manure and organic manure.

Green manure is a type of cover crop grown primarily with mixing of green crop with soil. It adds nitrogen and organic matter to the soil for the improvement of crop yield. Green manuring also improves soil aeration and drainage conditions. For green manuring, both leguminous and non-leguminous crops are used.

Organic manure improves soil fertility by adding organic content. Organic manures are of several kinds. Farmyard manures are readymade manures. Solid and liquid excreta as dung and urine of all farm animals are termed as farmyard manures. Compost manure can be prepared from a variety of refuge materials such as straw, sugarcane, forest Utter, kitchen wastes. The ideal method of storage of the organic manure is under anaerobic conditions at a temperature of 26 °C. The manure heap gradually looses nitrogen and the best hope of improvement lies in storing the manure in watertight pits, so made that they can be completely closed.

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Elaborate the following : 
VAM 


 Versicular arbuscular mycorrhiza 
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Expand the following:

DDT


Dichloro diphenyl trichloroethane

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Give reasons for the following:                                                                      
Nitrogenous fertilisers are not applied in fields where leguminous crops grow.


Nitrogenous fertilisers are not applied in fields where leguminous crops grow as the roots of leguminous crops contain nitrogen-fixing bacteria such as Rhizobium or Azotobacter, which fix the free nitrogen of the atmosphere into nitrates. Thus nitrogen is already made available to the plants and there is no need to add nitrogenous fertilisers. 

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