Multicellular organisms communicate with, and control their various parts by means of two major systems- the nervous system (absent in plant) and the endocrine system. The two systems, through diverse in their functions, coordinate their activities so that internal body harmony and balance is maintained. The hypothalamus, a major nerve center in t . . .
Homeostasis is a state of equilibrium produced by a balance of functions and of chemical composition within an organism. Example: The body produces more red blood cells to cope with the lack of oxygen at high altitudes. In other words, the internal system of the body adjusted to the change in external environment for the survival of the organism. . . .
1.Cretinism: it is caused due to undersecretion during growth years. It two main effects are: Dwarfism: due to failure of the skeleton to grow and mature. Mental retardation: due to failure of the brain to develop fully Cretins also show retarded sexual development, yellowish skin colour, round face, large thick producing to . . .
Types of WBCs . . .
RBCs (Erythrocytes) Structure Biconcave, disk shaped, colourless (red due to haemoglobin), spongy, flat at center & thick & round at periphery. 2 micron in size. Count About 4.5 to 5 million / mm3 but in infants 6 – 7 million / mm3 Its count lowers by 5% during sleep & increases during pregnancy & emotion . . .
Fraternal Twins (Produced from two eggs) Some times two eggs are released from ovaries at a time and both may get fertilized to produce two individuals. Such twins produced from two eggs are called fraternal twins. Fraternal twins may be either both boys, or both girl, or one boy and one girl. Also known as Diovular or Dizygotic twins. About . . .
Useful role of Bacteria In Medicine (i) Production of antibiotics 1. Antibiotic – An antibiotic is a chemical substance produced by a living organism which can stop the growth of some disease producing bacteria and fungi e.g. streptomycin, chloromycetin, tetracycline, penicillin etc. 2. Penicillin is the first produced antibiotic discovered by . . .
Accommodation of Eye for near & distant objects This is the process of focusing of eye at different distances. • Mainly brought about by a change in the curvature of the elastic lens making it thinner& fatter. • For distant objects the lens become more flattened or thinner. • For near vision (nearer than 6 meter) the lens be . . .
To prevent spoilage of food the food is preserved & made germ free by some techniques under food preservation. (a) Boiling or heating – Boiling water kills bacteria & at increased pressure it kills even spores so the canning industry employes heating to kill bacteria before packing & sealing food. (b) Salting – Used to . . .
Q. Why is the cell called the structural and functional unit of life? Ans. Each living cell has the capacity to perform certain basic functions that are characteristic of all living forms. Each cell has some specific components in it known as cell organelles. Each cell acquires its structure and ability to function because of the organisation of its . . .
Regulation of organic metabolism and energy balance: All protein, fat and carbohydrate metabolism is influenced by thyroxine. Since the overall effect is to increase catabolism, they increase the basal metabolic rate (BMR). The energy produced raises the body temperature. Regulation of growth and development: They regulates tissue (especially . . .
Q. Which organelle is known as the powerhouse of the cell? Why? Ans. Mitochondria are known as the powerhouse of cell. Mitochondria contain enzymes for catalysing biochemical reactions involved in respiration. Energy in the form of ATP is produced in the process. For this reason, mitochondria are generally called powerhouses of cell. . . .
Q. Explain the structure and the functions of the nucleus. Ans. Nucleus is the largest cell organelle. Most of the cells have single nucleus. It is spherical or oval in shape. It is surrounded by double membrane called nuclear membrane and contains a colourless, dense fluid called nucleoplasm. In nucleoplasm, some spherical bodies are embedded called . . .
Q. What is classification? Classify the plants on the basis of size and shape. Answer: Classification: Classification means grouping things together on the basis of certain common features. It is actually the method of putting similar things into one group. On the basis of their size and shape, plants have been divided into the following three cat . . .