What is Scuba?
Scuba is an acronym for Self-Contained Underwater Breathing Apparatus. It consists of a portable breathing device that can be carried by free swimming divers. Basically it is nothing but a mouthpiece joined to one or two tanks of compressed air which are strapped to the diver's back. The equipment makes it possible for divers to venture deeper into the waters than they would have been able to without it.The first aqualung was made in 1943 by Captain Jacques-Yves Cousteau and Emile Gagnan.
Sleep debt is a term used to describe the physiological phenomenon by which a person who has not had his usual quota of sleep for some time compensates for the lost sleep. A few hours of sleep everyday is a must for all. If a person who usually sleeps for 6-8 hours a day goes without sleep for a few days, he would sleep for much longer hours when he next goes to sleep. The more the number of days he is deprived of sleep, the longer will be the duration of the compensatory sleep. This proportionate increase in the hours of sleep in relation to the hours of sleep lost is due to sleep-debt. It is as if the body keeps count of the number of hours of sleep lost and makes up for it by going to sleep for proportionately longer periods.
Test tube baby is a term commonly used for babies born after being conceived outside the body. In normal pregnancy conception occurs when a sperm meets an ovum and fertilizes it inside the mother’s body. The fertilized ovum then implants in the wall of the uterus for the continuation of pregnancy. In cases where problems exist, in vitro fertilization offers a way out.
A transgenic organism is a plant or an animal whose cells contain, besides their own genes, foreign genes that have been introduced for achieving a specific purpose. Such transgenic species may contain one or many select foreign gene(s) endowing them with the ability to produce special protein molecules of choice.
Any sound of frequencies above the limit of human hearing, that is, 20,000 hertz or more, is called ultrasound. Ultrasound or ultrasonic waves are generated by devices called transducers that convert electrical, mechanical, or hydraulic energy into ultrasonic energy. The intense ultrasound waves generated by these devices can pack enough energy to break kidney stones (a process called lithotripsy); destroy harmful tissues in the brain and force dust and grease off delicate metal surfaces. They can cause liquids such as oil and water that normally would not mix to do so.
Vaccines are preventive medicines which when introduced into the body protect it from a specific disease-causing agent. These are usually derived from the disease-causing agent itself which may be a microbe like bacteria or virus, or a toxic microbial product called toxoid.
The pacemaker is a battery operated electronic device which transmits electrical impulses to the heart to keep it beating in a regular manner.
Nitrogen is essential for plants and animal life as it is a constituent of major bimolecules like proteins and nucleic acids. It is available in plenty in the atmosphere. However, for plants to be able to use it efficiently, it has to be converted into some nitrogenous compounds. This conversion is called nitrogen fixation. Nitrogen in the combined form is also necessary for the manufacture of explosives and chemical fertilizers.
A change in the structure of a gene resulting in an altered gene product, that is a protein, is called mutation. Most mutations have harmful effects in an organism. But a few may result in changes which can make that organism better adapted to its environment. In that case, natural selection acts to increase the frequency of the advantageous trait leading to evolution.
A state of exhaustion experienced by air travellers when they cross several time zones in a relatively short time as when one flies from India to U.S.A.. The condition arises from disturbances in the body’s habitual rhythms of ‘internal clock’ by suddenly requiring it to adapt to a strange new 24-hour time-scale.
Human genome refers to the entire genetic make-up of humans. The genes giving rise to specific human characteristics, their variants and the regulatory genes that direct the functioning of other genes are collectively called the “human genome”. Roughly a lakh genes are contained in about three billion base pairs present in every human cell. The international effort known as the “Human genome project” has published a draft of the human genome. This will help identify and locate all the genes and their variants, as well understand their functioning. The project was aimed at producing a human genome map containing the entire sequence of nucleotides in the human DNA.
Quicksand is a bed of loose sand mixed with water. It is found in places such as river banks and sea coast where there is a layer of impervious clay below. Although it looks like solid ground, quicksand cannot support weight and any person stepping on it may sink and get trapped. This happens because the water seeping in from the nearby water body remains trapped in the quicksand because of the impervious bottom underneath.
Heatstroke is a condition when the heat regulating mechanism of the body breaks-down. Sunstroke is a form of heatstroke caused by exposure to the sun for a long time. The very young and very old people are mostly at risk from heatstroke because their body-temperature regulating mechanisms are not very efficient. There are several other factors responsible for heatstroke. People who are unused to heat, overweight, heavy drinkers or are suffering from fever may be at a greater risk.