NEETians way

  Facebook  STRUCTURE OF MICROSPORE OR POLLEN GRAIN : pollen grain is the first cell of a male gametophyte. Pollen grain is termed as immature male gametophyte. Usually, they are in round shape. Pollen grain surrounded by two distinct layers. The outer layer (wall) is thick, rigid and ornamented, called exine . This layer is formed by cutin and sporopollenin , Sporopollenin is highly resistent material.  It is nonbiodegradable. Due to the presence of sporopollenin, fossils of pollen grain are always found in good condition. The presence of fossils of STRUCTUREOF POLLENGRAINS pollengrains can forecast the presence of natural resources like petroleum, coals etc. in the earth. The internal layer is thin, soft and elastic in nature. It is called intine . It is made up of pectin and Cellulose or pecto-cellulose . Usually, at few places on outer surface exine is absent or present in the form of thin layer. These thin places are called germ pore. The intine comes out through the any one ger

  WBC WBC (White Blood Corpuscles) are also called as leucocytes because they are colourless. TLC- Total leucocyte count Number of WBC /mm 6000 - 8000/mm (2000-3000) DLC :- Differential leucocyte count: number/ (%) of different type of leucocyte in per cubic mm. of blood. Acidophils    -    2-3% of TLC Basophils     -    0.5% -1% TLC Neutrophils   -    60 -65% TLC Monocytes    -    6-8% TLC Lymphocytes  -    20-25% TLC Leucocytosis :- Increase in TLC. This condition occur in bacterial & viral infection. Leucocytopenia :- Decrease in TLC. Normally TLC increases in bacterial & viral infection but in typhoid &  AIDS, TLC decreases. Leukemia :- Abnormal increase in TLC (more than 1 Lakh) it is called as blood cancer. On the basis of nucleus & nature of cytoplasm, Leucocyte are of two type 1. Granulocytes   a) In their cytoplasm granules are present which can be stained by specific dye.    b) Nucleus is multilobed and lobes are interconnected by protoplasmic strand.    c) D

  MECHANISM OF MUSCLE CONTRACTION Mechanism of muscle contraction is best explained by the sliding filament theory which states that contraction of a muscle fibre takes place by the sliding of the thin filaments over the thick filaments. Muscle contraction is initiated by a signal sent by the central nervous system (CNS) via a motor neuron. A motor neuron alongwith the muscle fibres connected to it constitute a motor unit. The junction between a motor neuron and the sarcolemma of the muscle fibre is called the neuromuscular junction or motor-end plate. A neural signal reaching this junction releases a neurotransmitter ( Acetyl choline ) which generates an action potential in the sarcolemma. This spreads through the muscle fibre and causes the release of calcium ions into the sarcoplasm. Increase in Ca++ level leads to the binding of calcium with a subunit of troponin on actin filaments and thereby remove the masking of active sites for myosin. Utilising the energy from ATP hydrolysis

  CARTILAGE Outer most covering of cartilage is called Perichondrium which is composed of white fibres connective tissue. Cartilage producing cells are arranged on periphery of cartilage known as Chondrioblast . These are active cell & divide to f orm chondriocytes, and synthesize the matrix of cartilage. Mature cells of cartilage is called Chondriocytes. They are found in vacuole like space in matrix called Lacuna . In which 1 - 4 Chontrocytes are present. Chondrioclast are cartilage destroying cells. Matrix of cartilage is called chondrin composed of chondromucoprotein having Chondrotin-6-sulphate and mucopolysacchride (Hyaluronic acid) Matrix of cartilage provides rigidity & elasticity to cartilage. (Matrix solid, Pliable and resists compression) Blood circulation is absent in the matrix of cartilage but blood supply present in perichondrium. Type of Cartilage — There are following types of cartilage 1. Hyaline Cartilage. 2. Fibrous Cartilage (a) Elastic cartilage (b) White

Ammonia, urea and uric acid are the major forms of nitrogenous wastes excreted by the animals.  Ammonia is the most toxic form and requires large amount of water for its elimination, whereas uric acid, being the less toxic, can be removed with a minimum loss of water. On the basis of type of excretory products (ammonia, urea and uric acid, three types of animals are present) Ammonotelics : Most aquatic animals excrete nitrogenous waste as ammonia. Ammonia is readily solutie soluble so generally it is excreted by diffusion across body surfaces or thought gill  surfaces (in fish) as ammonium in Kidney do not play significent role in its removal e.g. of ammonotelic animals are teloest (many bony fish), aquatic amphibians (tadpoles), aquatic reptiles and aquatic insects etc. Ureotelics : Animals like mammals, many terrestrial amphibians, marine fish excrete urea and are called Ureotelic. Ammonia produced by metabolism is converted into urea in the liver of these animals and released into t

  Genetically engineered insulin and how   it has been synthesized.  Genetically engineered insulin has been obtained from bacteria E. Coli by introducing human insulin gene in them.  Insulin obtained from other animal caused allergy and other type of reaction in the patient using it. Insulin consists of two short polypeptide chain A and B . They are linked by disulphide bonds. In human beings it is synthesized as pre hormone which needs to be processed before it becomes functional hormone . The prohormone contains an extra peptide C which is not present in mature insulin.  Recombinant DNA was applied to get insulin from genetically modified bacteria E. Coli. DNA sequences coding for peptide A and B of human insulin were prepared. These were introduced into plasmids of E. Coli. These separate chains were extracted from E. Coli in vitro and were joined together by disulphide bonds to get functional insulin or "humalin" .  This recombinant hormone is now been produced at large

Ramapithecus - Australopithecines - homo habilis - Homo erectus- Neanderthal man - Homo sapiens Modern primates are the end products of evolutionary process that began some 65 mya from shrew like insectivores. The firstly recognisabe anthropoid in the primate fossil record were discovered in the Fayum depression of Egypt. About 15 mya ,primate called Dryopithecus and Ramapithecus existing. About 3 - 5 mya, man like primates existed in Eastern Africa. They were probably 4 feet long and walked up right. About 2 mya Australopithecines  lived in East Africa grasslands. They hunted with stones and ate fruits. The first human like being was the hominoid the Homo Habilis.  Their brain capacities were between 650-800cc. About 1-5 mya fossils of next stage human the Homo erectus were discovered from java in 1891. Their brain capacities were 900cc and probably ate meat. About 100000-40000 years back Neandarthal man with brain capacities of 1400cc lived east and central Asia.  About 75000-10000