biology notes class

PEST OF RICE (SITOPHILUS ORYZAE) Distribution Sitophilus Oryzae is also called as Rice weevils. These insects are cosmopolitan in distribution and have originated in Far East region. They can exist anywhere where physical conditions for growth are favourable and the grain is left undisturbed for some time. Habit and Habitat Sitophilus Oryzae is usually found in grain storages and processing plants. They infest wheat, oats, rye, barley, rice, and corn. Sometimes, they are also found infesting beans, sunflower seeds and dried corn. These insects do not bite nor damage wood. Identification Weevils have chewing type of mouthparts. The most significant identification feature of weevils is their snout, which is pretty long. The adult rice weevil is reddish-brown in color. It has irregularly shaped pits on its thorax, also four light spots are found on wing covers. Rice weevils can fly. During larval stage they are legless, white to creamy white in color, with a small head. Weev...

PEST OF OILSEED (ACHAEAJANATA) Host:  This is a pest of castor, pomegranate, rose,  Zizyphus, Euphorbia, Tridax, Cardiospermum, Ficus, Bauhinia,  Citrus, mango etc. Damage:  Larvae defoliate plants quickly by feeding gregariously and voraciously. Midribs and veins are left intact and other parts of the leaves eaten up. Being larger in size, their capacity to cause damage is enormous. Young plants cannot sustain damage and die. Adults are fruit-sucking moths that prefer to suck juice from mango and citrus and fruits. Life cycle:  Adult moths are grayish-brown in colour with wavy lines on the fore wings. Hind wings are black in colour and have one large median and three marginal white spots. They are medium sized robust moths. Eggs are round, bluish green in color, ridged and are laid singly on tender shoots, usually on the undersurface of the leaves. Fecundity of a female is 450 eggs. Incubation period varies between 2-5 days after which a tiny larva hatc...

PEST OF SUGRACANE (PYRILLA PERPUSIELLA) Host:  This insect is a serious pest of sugarcane in northern India where it also occasionally feeds on maize, millets, rice, barley, oats, sorghum, bajra and wild grasses. Damage:  The pest is found gregariously on the under surface of the leaves where they suck up plant sap that causes yellowing and eventually drying of leaves. Under low infestation yellow patches appear on the leaves. Photosynthesis is reduced resulting in the reduction of sucrose content of the juice by up to 30%. Hoppers secrete a sweet substance called honey dew that coats the leaves and attracts a blackish fungus, which reduces photosynthesis resulting in yield loss. Life cycle:  Adult hoppers are straw coloured to brownish, 7-8 mm long, with a pointed snout bearing piercing and sucking mouth parts. They are found gregariously and jump off readily when disturbed. Adults are active fliers, migrating from one crop to another and breed throughout the year....

TUBERCULOSIS Tuberculosis (TB) is an infectious disease caused by the bacterium,  Mycobacteriumtuberculosi . TB most commonly affects the lungs but can involve almost any organ of the body. There is also a group of organisms referred to as atypical tuberculosis. These involve other types of bacteria of  Mycobacterium family. At times, these bacteria can cause an infection that sometimes appears as typical tuberculosis. These “atypical” mycobacteria are:  M. kansasii  that may produce similar clinical and pathologic symptoms of disease.  M. avium-intracellulare  (MAI) seen in persons with AIDS and is not primarily a pulmonary pathogen but occurs mostly in organs of the mononuclear phagocyte system. Tuberculosis outside the lungs can appear in the following kinds: SkeletalTuberculosis : Tuberculous osteomyelitis, known as  Pott’s disease,  involves mainly the thoracic and lumbar vertebrae followed by knee and hip. There is extensive necrosis a...

CHOLERA Cholera is an acute intestinal infection caused by ingestion of food or water contaminated with the bacterium  Vibrio cholerae . It has a short incubation period of one to five days and produces a toxin that causes painless, watery diarrhoea and vomiting that can quickly lead to severe dehydration and death. The genus  Vibrio  consists of Gram-negative straight or curved rod-like bacteria, with a single polar flagellum. Vibrios are capable of both respiratory and fermentative metabolism. Most species are oxidase-positive.  V. cholerae  and  V. parahaemolyticus  are pathogens of humans.  V.parahaemolyticus  is an invasive organism affecting primarily the colon, while  V.  Another species,  Vibrio vulnificus  is another emerging pathogen of humans that causes  cholerae  is noninvasive affecting the small intestine by producing an enterotoxin. wound infections, gastroenteritis or a syndrome known as “pri...

FILARIA Filariasis is an infectious tropical disease caused by three thread-like parasitic filarial worms,  Wuchereria bancrofti, Brugia malayi,  and  Brugia timori , all transmitted by mosquitoes. Lymphatic Filariasis, known as  Elephantiasis  puts at risk more than a billion people in more than 80 countries. Over 120 million are already affected by and over 40 million of them are seriously incapacitated and disfigured by the disease. One-third of the infected people live in India, one third in Africa and the rest are in South Asia, the Pacific and the Americas. PATHOGENS Pathogenic filarial parasites affect the lives of millions of people, especially those living in tropical countries. The filarial parasites that pose the most serious public health threats are  Wuchereria bancrofti, Brugia malayi, Brugia timori, Onchocerca volvulus , and  Loa loa.  All of these cause cutaneous manifestations. One filarial nematode,  Mansonella strepto...

  Sickle-cell disease Distribution of malaria.The best-studied influence of the malaria parasite upon the human genome is the blood disease, sickle-cell disease. In sickle-cell disease, there is a mutation in the HBB gene, which encodes the beta globin subunit of haemoglobin. The normal allele encodes a glutamate at position six of the beta globin protein, while the sickle-cell allele encodes a valine. This change from a hydrophilic to a hydrophobic amino acid encourages binding between haemoglobin molecules, with polymerization of haemoglobin deforming red blood cells into a “sickle” shape. Such deformed cells are cleared rapidly from the blood, mainly in the spleen, for destruction and recycling. In the merozoite stage of its life cycle the malaria parasite lives inside red blood cells, and its metabolism changes the internal chemistry of the red blood cell. Infected cells normally survive until the parasite reproduces, but if the red cell contains a mixture of sickle and nor...

MALARIA Malaria is one of the most common infectious diseases and an enormous public health problem. The disease is caused by a protozoan parasites of the genus  Plasmodium,  which is usually referred to as malaria parasites. The term malaria originated from the medieval Italian term,  mala aria  meaning “bad air” and the disease was formerly called marsh fever due to its association with swamps. In 1880, a French army doctor working at the military hospital in Algeria named  Charles Louis Alphonse Laveran  observed malarial parasites for the first time inside the red blood cells of people suffering from malaria. For this and later discoveries, he was awarded the 1907 Nobel Prize for Physiology or Medicine. The protozoan was named  Plasmodium  by the Italian scientists  Ettore Marchiafava  and  Angelo Celli . A year later,  CarlosFinlay , a Cuban doctor treating patients with yellow fever in Havana, first suggested that...

AIDS AIDS stands for Acquired Immunodeficiency Syndrome. It is the most advanced stage of infection with the Human Immunodeficiency Virus (HIV) which kills or damages cells of the body’s immune system. HIV most often spreads through unprotected sex with an infected person, by sharing drug needles or through contact with the blood of an infected person. Women can give it to their babies during pregnancy or childbirth. The first signs of HIV infection may appear as swollen glands and flu-like symptoms which may come and go a month or two after infection. Severe symptoms may not appear until months or years later. The CD4 count indicates how far the HIV disease has advanced. CD4 counts in adults range from 500 to 1,500 cells per cubic millimeter of blood. In general, the CD4 count goes down as HIV disease progresses, to below 200, regardless of whether the persons are sick or not. MODE OF INFECTION Once HIV enters the human body, it attaches itself to a White Blood Cell (WBC) call...

VERMICULTURE Vermiculture means worm farming or culturing worms for selling them either to fishermen or to compost manufacturers. When earthworms are used for the production of compost it is called  vermicomposting. Earthworms burrow through the soil and feed on decaying organic matter, excreting castings that are rich in nutrients and beneficial micro-organisms, which are about 20 times more in worm castings than in normal soil. These beneficial organisms not only make available nutrients to the plants but also suppress the growth of pathogens leading to healthy plants. The most common worms used in vermiculture are, red worms  (Eisenia foetida, Eisenia andrei,  and  Lumbricus rubellus).  These worms thrive at temperatures between 20-30°C and can be cultured indoor in boxes. Other worms like  Perionyx excavatus  and  Eudrillius eugiene are are suitable for warmer climates. Vermiculture Medium Crop residues, dry leaves, cattle dung are the...