FST - 1

5th Part 

Q.  With the help of a neat labeled diagram describe the 'feedback' mechanism which checks the loss of water from kidneys in the human body. What is it technically known as? 

Q.  Define homeostasis with example

A. Living organisms have a remarkable capacity to regulate their own lives according to the changes in the environment around them. They maintain a normal external and internal structure and environment in spite of the changes taking place in the outside surroundings. This state of constant structure which is vital for life is known as 'homeostasis'.

            One example of the feedback system in the human body is the availability of the right amount of water in the blood due to the functioning of kidneys. Kidneys are able to control or check the loss of water from our bodies. For this, water is reabsorbed by the collecting tubes in the kidneys so as to prevent its undue loss in the form of urine. This absorption of water is under the control of a chemical called Antidiuretic Hormone (ADH) which is produced by specialized nerve cells in one of the parts of the forebrain. If more water begins to be lost by the body due to greater evaporation during summer, a decrease of water in the blood will take place. It denotes the changes in the internal environment for which our body is very sensitive. At the time of need, a positive signal to the brain causes the production of this particular chemical (ADH) which increases the absorption of water in the kidneys and reduces excretion of urine. The absorbed water gets back into the blood to maintain the normal concentration of the fluid.

Q.  Why is Mars called red planet and in what ways is it similar to earth?    

A.    Mars is often called the 'Red Planet' because it appears in the sky as an orange-red star. The reason for the red color of Mars is because, about 16 percent of the Mars soil is made up of iron oxide, giving it its red color.

         Mars seems very earth-like. There are ice-caps on its poles, drifting white clouds, and raging dust storms in its atmosphere. Seasonally changing patterns also occur on the red planet. There are large dark areas on its surface called maria (meaning 'seas'). It even has a twenty-four-hour day. Mars experiences summer and winter seasons, each of which lasts for almost six earth months.

         The atmospheric pressure on Mars is very low. It is comparable to what it is on the Earth at a height of 32 km from sea level. Thus, Mars has a very thin atmosphere. It is made up of 95 percent carbon dioxide. The rest is nitrogen, argon and a small amount of water vapor. Tiny amounts of hydrogen, oxygen, and ozone have also been detected. Though the Martian atmosphere has clouds of frozen water, carbon dioxide and of reddish dust, it does not contain enough gases to trap the Sun's heat. This makes Mars a very cold planet. The surface temperature may rise to 21°C or 27°C near its Equator, at noon. But, during the night, it becomes as low as-84°C. The present conditions on Mars-cold, extreme dryness, intense ultraviolet light and little oxygen-are hostile to the familiar forms of life. The Viking space probes, send by U.S.A.did experiments on Mars which showed no signs of life.

           Like Earth, the Martian surface has deep ridges and valleys. Pictures also show islands made where water once flowed and river beds which are dry for hundreds of millions of years. The surface features indicate that Mars may have had both the atmosphere and ocean in the past. Martian surface has craters of sizes, ranging from 5 km to 121 km in diameter, created by meteorite impact. It also has enormous volcanoes. The largest volcano on Mars Mount Olympus is nearly three times as high as Mount Everest. Martian soil is mostly like the Earth's soil made up mainly of silicates. 

Q.  Write any five features of the planet Jupiter. How would you differentiate it from the Red Planet?                               

A. #  Jupiter is the largest planet of the Solar System.

#  It weighs more than twice as much as all the other eight planets put together. It has sixteen known satellites. Jupiter is not only the biggest planet but also the liveliest.

#  Its highest clouds are mainly crystals of frozen ammonia gas at a temperature of about -140C. It is veiled in a turbulent, gaseous atmosphere made up of hydrogen and helium with significant amounts of ammonia and methane.

#  At its center, Jupiter has a small rocky core where temperatures reach 20,000"C, about three times the temperature of the Sun's surface. There are iron, silicon and other heavy elements in the rocky core. Jupiter seems to be more like the Sun in its composition than the other planets.

#  Jupiter is mainly a quick-spinning ball of gas and liquid with no solid surface. It also emits radio waves. Its composition, size and the number of moons gave rise to the idea that Jupiter is not a planet but rather a star with a "solar system" of its own, that did not start 'burning'. It is estimated that if Jupiter, were just ten times heavier, it could have started to produce its own energy like the Sun.

Q.  Differentiate between chemical evolution and biological evolution.     

A.  Chemical evolution -  the formation of organic molecules from inorganic molecules is referred to as chemical evolution. Chemical evolution describes chemical changes that took place on primitive earth that give rise to first life forms. Around 4 Billion years ago, the earth's atmosphere consisted of chemicals such as water vapour, Methane, Ammonia, and hydrogen. The waters of this stage of the Earth's development have been referred to as "hot dilute soup", which amongst other things also contained "amino acids" having a composition of carbon, hydrogen, nitrogen and oxygen. The molecules of amino acids combined together to form large complex molecules, the "proteins" which are the building blocks of life. It is from this accumulation of complex organic molecules that the first extremely simple self-replicating molecular systems accidentally originated. Because of the property of self-replication, they are called living organisms.

Biological Evolution -  the enzymes proteins once formed during the chemical evolution process leads to self-replicating molecular systems which further evolved over a period of time, into membrane-bound protocells and finally transformed into living cells. This process is called biological evolution. Biological evolution thus refers to the slow and gradual process by which living organism has changed from the simplest self-replicating molecular systems form to the most complex multicellular forms that exist today. Biological evolution primarily involves modifications in the existing organisms and the inheritance of these modifications. During this stage, first cells capable of using carbon dioxide and energy from light, to make their own food through photosynthesis emerged.

Q.  Comets                   

A.  The cold outer areas beyond Pluto are the regions of comets. When the solar matter was churning and the Sun had just been ignited, its heat drove, the lighter elements into the outer reaches of the Solar System. Hydrogen, oxygen, nitrogen, and carbon collected into something like snowy cotton balls and they still float as a "cloud", at a distance of 100.000 times the distance of the Earth from the sun. Comets are made mainly of 'ices', that is ordinary water mixed with frozen gases such as methane, carbon dioxide, and ammonia. The ices are mixed with specks of dust that makes them look like dirty snowballs. While still in this cloud, comets do not shine. Once in a while, the gravity of a passing star attracts this cloud. A few comets then move into interstellar space and are lost to the Solar System. Others move towards the Sun.

             As a comet moves towards the Sun, its surface is heated up by the strengthening sunlight. Some of its frozen material turns into gas, forming a rapidly growing cloud around its center which is called its head or coma. On getting nearer to the Sun, more gas evaporates and its head becomes bigger and brighter. Also, a brilliant tail, made of dust and gas, is pushed out of the head by the pressure of the sunlight and the solar wind. This tail extends in a direction away from the Sun. One of the most famous comets is Halley's Comet which returns once every 74 to 79 years. It was last seen in 1986. Sometimes fragments from the comets fall on the Earth producing meteors. Comets returning repeatedly lose their gases each time. When all their ices melt, comets disintegrate, leaving a stream of small particles that spreads out thinly and loses its identity.

Q.  Write a brief note about Neptune and Pluto                     

A. Neptune - The eighth planet of the solar system, Neptune, was discovered in 1846 by astronomer Johann Gottfried Galle. Neptune's atmosphere has methane but no detectable ammonia. Its cloud temperature is about -237°C. Neptune is orbited by Triton, one of the biggest satellites in the Solar System. It orbits Neptune in a clockwise direction, i.e. opposite to the planet's own rotation. It has an atmosphere of nitrogen and methane. It may even have an ocean of liquid nitrogen. Triton is accompanied by a smaller satellite, Nereid. In 1989, Voyager 2- passed within 35,000 km of Neptune and within 40,000 km of Triton.

Pluto - Pluto is the ninth and the farthest planet from the sun. In 1916, Pluto was discovered however, its mass is even less than our Moon. Small, cold and dark, Pluto is about one-fifth of the size of the Earth. Its surface is coated with frozen methane. In 1938, a satellite of Pluto was discovered and named Charon. Not much is really known about Pluto. Pluto's orbit crosses that of Neptune's. No other planetary orbits cross in this way, and it is possible that Pluto is an escaped satellite of Neptune.

Q.  What observations led to the discovery of planet X still on?   A. Pluto was earlier supposed to make for deviations in the orbit of Uranus. Even after the influence of Neptune had been accounted for, an American astronomer Professor of Physics, detected that the orbit of Uranus was still disturbed. Neptune's orbit too showed similar disturbances. Scientists calculated and predicted the mass and radius of the orbit of Planet X which was supposed to cause these disturbances. Pluto's discovery had led astronomers to believe that it was Planet X. But now calculations show that the mass of Pluto is too low to cause irregularities in Uranus' orbit. Thus, the search for the elusive Planet X goes on.

Q.  Explain Darwin's theory of Natural Selection. Why was it not acceptable to most people of that time?                       

A. Darwin’s theory of Natural selection was based on two observations. First. more organisms are born in nature than can survive to reproduce themselves. This is because the environment has limited resources for subsistence. This overproduction results in a struggle for existence and ultimately leads to the survival of the fittest. Plant and animal species compete within and among themselves for food, water, air, light-everything that enables organisms to survive and reproduce. The second observation is that offspring, i.e, children differ slightly from their parents and from each other in characteristics that they inherit. This we now call genetic variations. Darwin held the view that these variations are a source of evolutionary change. According to him in any group both plants and animals, individuals with characteristics that enable them to adapt best to their environment survive and reproduce, while those who lack these characteristics have a poor chance of survival. Thus, Nature selects and preserves the favorable characteristics or useful variations in a changing environment, Darwin called this natural selection. Darwin's theory of evolution through natural selection was based on observations as well as the other existing information of that time. Through his analysis, he not only gave the theory of evolution but was able to give us a mechanism for evolutionary change.

               Darwin's theory of Natural Selection was not acceptable to most people of that time including the Church as it was a radical theory and spoke against special creation or the theory of divine creation by god which was proposed by Church and is uniformly accepted by the society. In fact, Darwin was very severely criticized for his views. However, he got support from scientific circles. The debate went on for quite a few years and continues even today between the men of science and those of religion.

Q.  Write about the most important current theory for the origin of the universe. Describe any two pieces of evidence that support this theory.         

Q.  What is the 'Big bang' theory regarding the origin of the universe? Explain the various evidences favoring this theory.      A. The most important current theory for the origin of the universe is the Big Bang theory. According to this theory, the universe started with a huge explosion. It was not an explosion like the ones with which we are familiar, which start from a definite center and spread out. It was an explosion that occurred everywhere in space at the same time. It filled all space from the beginning, with every particle of matter rushing apart from every other particle. This was not an explosion of matter into space but rather an explosion of space itself. Every particle of matter rushed away from every other particle. It is so far impossible to 'picture' the first moment of the 'creation' of the universe.

Evidence Favouring the Big Bang

The first evidence comes from the expanding universe which suggests that the matter was packed much more densely in the early stages of the universe. The proof for this also comes from distant objects called quasars. When we 'look' at quasars situated 6 to 8 billion light-years away, we are looking at them as they existed then. If the universe were more dense in that epoch, we should be able to see some evidence of that density in the quasars. We do see such high density among the quasars which proves the Big Bang theory.

      Another evidence for the Big Bang theory comes from the cosmic background radiation. For many years the astronomers believed that if there was a cosmic explosion long ago, radiation from that event should still exist within the universe. This radiation may be weak, it may have lost its energy due to the expansion and cooling of the universe, but it should exist. Radio-astronomers have successfully discovered faint signals -a constantly present radio noise in the background that pervades all space. Calculations done by astrophysicists show that this radiation, called the cosmic microwave background radiation, is a relic of the ancient past when the universe went through the Big Bang.

       An additional discovery made by astronomers in the past two decades is that of the primordial abundance of elements, i.e. the elements hydrogen and helium which are firstly created in the aftermath of Big bang. These elements are found to be most abundant in the universe. By examining the light coming from the various parts of the universe, astronomers have found out that, out of every 100 atoms, almost 93 are hydrogen atoms and seven are helium atoms. Elements heavier than helium are present in traces only. This suggests that the universe started out with a Big Bang from a very hot and dense state and quickly cooled as it expanded. The hot and dense conditions lasted long enough for some hydrogen to fuse into helium. But they did not last long to allow other heavier elements to form in significant amounts. These were made much later in the interior of massive stars. 

Q.  Explain the steady state theory.

A. There is another theory about the origin of the universe known as the steady-state theory. This theory holds that the universe has always been just about the same as it is now. As it expands, new matter is created continuously to fill up the gaps between the galaxies. Thus, the problem of the origin and early moments of the universe is banished there was no early universe. However, the Big Bang theory is the most favored by astronomers and astrophysicists.

Q.  Describe Kepler's laws related to planetary motion.          

A.  Kepler's three laws of planetary motion can be described as follows:

#  The path of the planets around the sun is elliptical in shape, with the center of the sun being located at one focus. (The Law of Ellipses). Kepler's first law states that - all planets orbit the sun in a path that resembles an ellipse, with the sun being located at one of the foci of that ellipse.

#  An imaginary line drawn from the center of the sun to the center of the planet will sweep out equal areas in equal intervals of time. (The Law of Equal Areas). Kepler's second law - sometimes referred to as the law of equal areas. It describes the speed at which any given planet will move while orbiting the sun. The speed at which any planet moves through space is constantly changing. A planet moves fastest when it is closest to the sun and slowest when it is furthest from the sun

#  The ratio of the squares of the periods of any two planets is equal to the ratio of the cubes of their average distances from the sun. (The Law of Harmonies).Kepler's third law - sometimes referred to as the law of harmonies - compares the orbital period and radius of orbit of a planet to those of other planets.

Q.  State the differences between paleontology and archaeology.      

A. Archaeology - The study of human antiquities, especially of prehistoric period is known as archaeology. The biological and cultural evolution of man proceeded side by side and the two influenced each other. Like the physical remains of man, his cultural remains also lie buried in the ancient deposits. Often, the two categories of evidence are found together in the same layers of the rock. With the passage of time and the increasing capacity of his brain and development in other bodily organs, man's culture became more and more varied and complex. He learned the use of new materials for making tools and developed new techniques for improving them. The use of tools had a tremendous impact on increased access to food and change in socio-economic conditions which has been discovered in archaeology.

Paleontology - Palaeontology is a branch of earth sciences, which is essentially a study of plant and animal life in the past geological periods, millions of years ago. It deals with the successive plants and animals which have inhabited the earth since the earliest times. Evidence of their existence is left in the form of skeletons and bones buried in the rocks. These are known as fossils. Crucial evidence of human evolution is provided by the study of these fossils.

                Sometimes, the buried body and the skeleton of an animal disintegrate entirely. If the surrounding material is sufficiently firm, it leaves a cavity having the exact outlines of the structures that disappeared. Such a cavity is called mold, Similar to molds are the impressions. These are left by extinct objects or parts of the body upon the Surrounding material. The impression is made while the surrounding material is soft, like footprints in clay or lava. Footprints of extinct animals are also impressions affording valuable information about the animals that made them.