HUMAN AND PLANT DISEASES AND THEIR CAUSES

**A synthetic fibre is also a chain of small units joined together. Each small unit is actually a chemical substance. Many such small units combine to form a large single unit called a polymer.

**Cotton, for example, is a polymer called cellulose. Cellulose is made up of a large number of glucose units.

**silk fibre obtained from silkworm was discovered in China

**Although rayon is obtained from a natural source, wood pulp.

**Nylon, it was made without using any natural raw material (from plant or animal). It was the first fully synthetic fibre.

**Polyester (Poly+ester) is actually made up of the repeating units of a chemical called an ester. Esters are the chemicals which give fruits their smell. Fabrics are sold by names like polycot, polywool, terrycot etc. As the name suggests, these are made by mixing two types of fibres. Polycot is a mixture of polyester and cotton. Polywool is a mixture of polyester and wool.

**Many of these are actually not made from natural wool, though they appear to resemble wool. These are prepared from called acrylic.

**synthetic fibres melt on heating. This is actually a disadvantage of synthetic fibres. If the clothes catch fire, it can be disastrous.

**All the synthetic fibres are prepared by a number of processes using raw materials of petroleum origin, called petrochemicals.

**plastic which gets deformed easily on heating and can be bent easily are known as thermoplastics. Polythene and PVC are some of the examples of thermoplastics.

**plastics which when moulded once, can not be softened by heating. These are called thermosetting plastics. Two examples are bakelite and melamine. Bakelite is a poor conductor of heat and electricity. Melamine is a versatile material. It resists fire and can tolerate heat better than other plastics.

**Teflon is a special plastic on which oil and water do not stick. It is used for nonstick coating on cookwares.

**Fire-proof plastics: Although synthetic fibre catches fire easily, it is interesting to know that the uniforms of firemen have coating of melamine plastic to make them flame resistant.

**Special plastic cookware is used in microwave ovens for cooking food. In microwave ovens, the heat cooks the food but does not affect the plastic vessel

**Serious diseases like polio and chicken pox are also caused by viruses. Diseases like dysentery and malaria are caused by protozoans whereas

typhoid and tuberculosis (TB) are bacterial diseases.

**Microorganisms may be single-celled like bacteria, some algae and protozoa, or multicellular, such as algae and fungi. Microorganisms like amoeba can live alone, while fungi and bacteria may live in colonies.

**the bacterium Lactobacillus promotes the formation of curd. It multiplies in milk and converts it into curd.

**process of conversion of sugar into alcohol is known as fermentation.

**Streptomycin, tetracycline and erythromycin are some of the commonly known antibiotics which are made from fungi and bacteria.

**Edward Jenner discovered the vaccine for smallpox in 1798.

**Anopheles mosquito, which carries the parasite of malaria. Female Aedes mosquito acts as carrier of dengue virus.

**Robert Köch (1876) discovered the bacterium (Bacillus anthracis) which causes anthrax disease.

**Foot and mouth disease of cattle is caused by a virus.

**Sodium benzoate and sodium metabisulphite are common preservatives.

**Rhizobium lives in the root nodules of leguminous plants

**In humans the sound is produced by the voice box or the larynx.

**The vocal cords in men are about 20mm long. In women these are about 5mm shorter. Children have very short vocal cords.

**The sound cannot travel through vacuum.

**Above 80 dB the noise becomes physically painful.

**naphthalene balls used to repel moths and other insects are also obtained from coal tar.

**The world’s first oil well was drilled in Pennsylvania, USA, in 1859. Eight years later, in 1867, oil was stuck at Makum in Assam.

**Due to its great commercial importance, petroleum is also called ‘black gold’.

Human Disease	Causative Microorganism	Mode of Transmission	Preventive measures (General)
Tuberculosis	Bacteria	Air	Keep the patient in complete
Measles	Virus	Air	isolation. Keep the personal belongings of the patient away
Chicken Pox	Virus	Air/Contact	from  those  of  the  others. Vaccination  to  be  given  at
Polio	Virus	Air/Water	suitable age.
Cholera Typhoid	Bacteria Bacteria	Water/Food Water	Maintain personal hygiene and good sanitary habits. Consume properly cooked food and boiled drinking water. Vaccination.
Hepatitis B	Virus	Water	Drink boiled drinking water. Vaccination.
Malaria	Protozoa	Mosquito	Use mosquito net and repellents. Spray insecticides and control breeding of mosquitoes by not allowing water to collect in the surroundings.

Plant Diseases	Micro- organism	Mode of Transmission
Citrus canker	Bacteria	Air
Rust of wheat	Fungi	Air, seeds
Yellow vein mosaic of bhindi (Okra)	Virus	Insect