Oceans and Rivers

Oceans cover around 71 percent of the earth’s surface and the remaining 29 percent is the land area. They are estimated to contain 1.3x10 18 tons of water. There are five oceans: the Atlantic, Pacific, Indian, Arctic and Antarctic. There are smaller bodies of water called seas, sounds, bays and gulfs. All of these are connected to each other.
The Pacific Ocean is the largest and the deepest. It covers an area of about 16, 62, 40,000 sq. km. the second largest is the Atlantic ocean which has an area equal to half of the Pacific Ocean. The Indian oceans are the third largest. It extends from Kanyakumari (Cape Comorin) in India to the South Pole, Antarctica. The Arctic Ocean surrounds the North Pole. It is completely frozen and unnavigable. Some people consider Antarctica also to be an ocean.
The ocean water is saline and not if for drinking. The average salinity is 3.5 percent. The main source of salinity of oceans is the water of the rivers that carry with them billions of tons of dissolved minerals every year.
Oceans exercise a great influence on climate. They are the main source of rainfall on the continents. Ocean currents regulate the temperature in the coastal regions. The sea breeze and the land breeze keep moving in their set directions. Due to the heat of the sun, the water in the oceans evaporates into smoke and converts into clouds that cause rainfall to make the soil fertile.

A river is a large stream of water that flows from high land to low land. The water in rivers comes from rain, snow melt, lakes, springs and water falls. The river water eventually flows into oceans.
There are many kinds of rivers such as- the swift flowing rivers, the slow moving rivers, the straight rivers, the meandering rivers, the large and the small rivers. The speed of flow of water in a river depends on the steepness. The rate of flow at the mountain slopes is higher than that in the plains. The course of river near its source is narrow but it widens as it moves downstream.
Some rivers owe their origin to melted ice in the mountains while others to the glaciers. A river is in youthful stage in mountainous region upper course, in mature stage in flat valleys mid course and in old stage in delta region lower course.
In the upper course the river flows zig-zag through the mountain blocks. Further downwards it develops land forms like gorges and canyons. In mid course, the river slows down but gathers larger volume of water from its tributaries and takes many turns. In the lower course, the river widens its bed and wends its way leisurely. Here, it forms flood plains, ox-bow lakes and deltas. The delta region consists of very fertile soil and silt. Rivers are a very useful means of transport and communication. Ships and boats sail on the rivers. Dams are constructed on big rivers to generate electricity, popularly known as hydroelectric power. Canals are cut from these big rivers to divert the water for irrigation purposes.


Sexual Reproduction in Animals

  Animals reproduce to continue their race. Animals reproduce both by asexual and sexual methods. Asexual reproduction occurs in the organisms of lower phyla like protozoa, coelenterate, porifera etc., Majority of the animals adopt sexual reproduction. Male sex organs are called the 'Testes' while the female sex organs are called the 'Ovaries' and they produce cells called 'Gametes' like spermatozoa (or) sperms and ova respectively.
          Fusion of gametes is called fertilization. Fertilization is of two kinds. When fertilization occurs inside the body of the female animal is called internal fertilization and when fertilization occurs outside the body of the animal, it is called external fertilization. In majority of the animals, sexes are separate and male and female animals are separate. This is called sexual Dimorphism and animals are said to be unisexual.
Conjugation in Paramoecium:
            Paramoecia, after repeated binary fissions, become weak and switch over to sexual reproduction known as conjugation.
The Paramoecia that undergo conjugation are called conjugants. The two conjugants come close and unite. The pellicle that separates them dissolves. The cytoplasm of the two paramecia becomes continuous through this part, where the pellicle is dissolved. This is called as cytoplasmic bridge. At this stage the macronucleus slowly disappears and the micronucleus undergoes meiotic division resulting in four haploid nuclei. Of these four nuclei, three disintegrate and the rest single micronucleus divides into small migratory (male) pronucleus and large stationary (female) pronucleus.
             The male pronucleus of one conjugant fuses with the female pronucleus of another conjugant through cytoplasmic bridge resulting in synkaryon. Then after the conjugants get separated and are called as exconjugants.
In each exconjugant, the synkaryon undergoes 3 mitotic divisions and form 8 nuclei. Of these eight, three disappears. Of the remaining five nuclei, four develop into macro nuclei and one into micronucleus.
              Each exconjugant, with a single micronucleus and four micronuclei divides twice and forms four daughter paramoecium. Each daughter paramoecium receives one macronucleus from the exconjugant.
              The single micronucleus of the exconjugant divides twice along with the exconjugant and each daughter paramoecium receives one micronucleus. Thus each of the daughter paramoecium receive one macro and one micronucleus. Thus, by conjugation a single paramoecium produces four daughter paramoecium
Different stages in the conjugation of Paramoecium

Reproductive System in Earth Worm
Earthworm is hermaphrodite - both male and female sex organs are present in the same individual. But, earth worm shows protandry condition that is the testes matures much earlier than ovaries and this prevents self fertilization. The testes are present one on each side of the body in 10th and 11th segments. They produce sperm mother cells which inturn matures into sperms in seminal vesicles. The sperms passes out through vas deferens and into male genital aperture.
          A pair of ovaries are present, one on each side of the ventral nerve cord. They arepresent in the 13th segment. Each ovary has one oviduct, which opens out through female genital aperture. Ovaries produce ova and the ova are sent out through an aperture.
A thick girdle like clitellum is formed in between 14-17 segments. When the ovaries mature, the clitellum secretes a viscous substance becomes sticky and attaches with the substratum.
This is called cocoon. Earth worm wriggles and retreats back leaving the clitellum. Eggs and sperm cells are released into this cocoon. Both the ends are closed and it gets hardened to form a cocoon. Fertilization occurs inside the cocoon.
Since fertilization is taking place outside the body, it is external fertilization. After about 8 to 10 weeks, young earthworms come out of the cocoon.

Reproductive System in Earth Worm

Cocoon Formation in Earth Worm

Reproduction in House Fly
In male fly, a pair of testes are present one on either side of the ventral cord. Testes produce sperms. Each testes is connected to a tube called vas deferens. The two ducts unite to form a single ejaculatory duct. It opens out through male genital opening. In female fly, a pair of ovaries are present in the abdominal segment. Each ovary is connected to a oviduct. The two ducts unite posteriorly to form uterus.
It opens out through female genital opening, and is located in a special structure called ovi positor which helps in releasing fertilized eggs. A pair of sperm theca are attached to the ovi positor. They store sperms received during copulation.
Fertilization is internal. The eggs are laid by the female from 6-8 weeks after copulation. The eggs are laid in a clustor in decaying organic matter like manure, cow dung, decomposing fruits and grass, human faeces etc.
Reproduction in House Fly
Reproduction in Frog:
Frog is unisexual and shows sexual dimorphism.
Male Reproductive system:
            The male reproductive system consists of a pair of testes, vas efferentia and a pair of urinogenital ducts. Testes is an oval and yellow body which is attached to a kidney. Inside the testes there are a number of coiled tubules called seminiferous tubules. Spermatozoa are produced in the tubules. Each testes opens into a kidney through 10- 12 tubes called vas efferentia. Spermatozoa enter the kidney through these tubes.
From kidney two tube-like structures called ureters enterinto a chamber called cloaca. The ureters in male frog are called urinogenital ducts.
Spermatozoa produced in seminiferous tubules of testis enter into kidney through vas efferentia and from kidney into cloaca through urinogenital ducts. Cloaca opens outside through cloacal aperture. The discharged spermatozoa is called milt.

Male Reproductive System in Frog
Female reproductive system of Frog:
           It consists of pair of ovaries and a pair of oviducts. A pair of lobed ovaries are attached to the kidneys. Ovary is a sac like structure which is greyish or blackish in colour. Inside the ovary, numerous chambers called "Follicles" are present. Each folliclegives a single ovum.
From each ovary long folded, tube like structure called 'oviduct' arises. This opens anteriorly into the body cavity through a ciliated funnel called Ostium.
Female Reproductive System in Frog

The funnel collects ova from the body cavity posteriorly. The oviduct is enlarged into a sac called ovisac or uterus. which stores ova. The oviducts open into cloaca and are discharged out through the cloacal aperture. Frog release a large number of eggs as a mass called Spawn.
The ovum of frog is spherical. In the upper part is the nucleus and this part is black due to pigment present in the cytoplasm. This part is called animal hemisphere. Yolk is concentrated at the other pole, which is whitish. This pole is called vegetal hemisphere.
Frog Ovum

Shock Waves

Shock waves is a wave of high pressure that forms in a gas or liquid as an object moves through it at or above the speed of sound or as the gas or liquid flows around the object. The shock waves are also called pressure waves and they move away from the object at the speed of sound. These waves contain high energy and are very dangerous. They are produced during cloud thunders, eruption of volcanoes and in lightening. Every year shock waves cause a big loss to many live and property.

 Shock Waves in Supersonic airplane
A shock wave is created in air when a super sonic airplane flies overhead at the speed of sound or faster. When the wave reaches the ground, a sonic boom is heard as the waves strikes the ears. A sonic boom can shatter the window panes.

 Shock Waves in Supersonic airplane
Explosions also produce powerful shock waves which can damage constructions up to several kms. Shock waves can also be produced by the high speed of the bullet of a gun. When the speed of a motor boat in water becomes very high, shock waves are created on the surface of water. Earthquakes also cause shock waves. Explosions of atom and hydrogen bombs create very powerful shock waves which can cause deaths to large number of people. Shock waves are also produced due to the explosion of chemical bombs.


All living organisms require energy for various metabolic activities. The energy is released through the process of respiration (where molecules like glucose and fatty acids are oxidised). Let us know how living organisms get energy through respiration by using oxygen.

Oxidation of food materials, especially glucose, fatty acids and proteins to CO2 and water is called Respiration. Energy is produced in this process. As this process occurs at cellular level it is called Cellular Respiration.
Cellular respiration is the process by which food is broken down by the body's cells to produce energy, in the form of ATP molecules.

Cellular respiration is carried out by every cell in both plants and animals and is essential for daily living. Energy is produced only when glucose and fatty acids are oxidised which are transported from the digestive system to all the other cells in the body which are carried by blood.

Respiratory Substrates:
Substances which oxidised in the body during respiration to produce energy are called respiratory substrates. In all organisms from microbes to man the major respiratory substrates are carbohydrates and fats.

Carbohydrates like starch and cellulose are complex molecules. Such complex molecules are not oxidised directly to produce energy. First of all complex molecules (carbohydrates) are broken down into simple molecules and then oxidised. Between these process so many reactions takes place. But energy is not produced in each and every reaction during the oxidation of glucose or fatty acids. Only in some of the reactions small amount of energy is produced. This energy is converted into chemical energy and is stored in ATP (Adenosine Tri Phosphate).

The ultimate goal of cellular respiration is to take carbohydrates, diassemble them into glucose molecules, and then use this glucose to produce energy-rich ATP molecules.
The general equations for cellular respiration is: One glucose molecule + 6 oxygen molecules produces six carbon dioxide molecules, 6 H2O and approximately 36 -38 ATP molecules.

Mitochondria - Sits of Cellular Respiration
Cellular respiration occurs in Mitochondria. Oxidation of food materials takes place in them. The energy released through oxidation is utilised by the mitochondria to synthesis ATP which are energy rich compounds. Therefore mitochondria are called as Power houses of the cell.

O2, ADP + Pi (inorganic phosphate), carbohydrates, fats are required for the respiratory activity in mitochondria.

  • Mitochondria are sac like structures present in the cytoplasm of the cells.
It has two compartments.
1. An inner compartment
2. An outer compartment
  • The substance in the inner compartment is called Matrix.
  • The inner membrane is thrown into several foldings called Cristae.
  • The space between the foldings is continuous with the outer compartment.
  • On the inner membrane large number of elementary particles are seen which have a spherical head and a stalk.
  • Outer compartment is surrounded by outer membrane.
  • Inner membrane, matrix and elementary particles have large number of enzymes which required for the respiration and energy production.
There are three main stages of cellular respiration.
1. Glycolysis
2. Krebs Cycle
3. The electron transport chain

First step in glucose oxidation is called glycolysis. (In the first stage of glycolysis energy is used to phosphorylate the 6-carbon glucose is used to molecule.) This means that a phosphate is taken from ATP (which becomes ADP) and added to the glucose molecule. This addition of phosphate makes the molecule much more energised and converted into glucose-6 phosphate. Later glucose-6 phosphate is converted to fructose-1, 6-Diphosphate. In this process another ATP is used. Fructose-1, 6-Diphosphate is finally converted into two molecules of pyruvic acid.

Result: 4 ATP and 2 NADH are formed. 2ATP molecules are used in this process. So, net gain is 2 ATP molecules.

Krebs Cycle
It takes place in mitochondrial matrix. This cycle involves series of reactions in which pyruvic acid is oxidised. This cycle discovered by Sir Hans Krebs, that's why it is called as Krebs Cycle.

When oxygen is available pyruvic acid molecules (end product of glycolysis) are converted into Acetyl Co-enzyme A with the release of CO2.

Acetyl Co-enzyme A is attached to oxalo acetic acid and formed into citric acid. When the two carbons are removed in the form of CO2 again oxalo acetic acid (4 C) is formed.

This combines with acetyl co- enzyme A and the cycle continues. So, this cycle is also called as citric acid cycle.

In this process small amount of energy is formed when two molecules of pyruvic acid are oxidised. Therefore 2 ATP molecules are gained.
Electron Transport Chain
Very little amount of energy has been produced during glycolysis and the Krebs Cycle. Most of the energy locked in the original glucose molecule will be released by the electron transport chain and oxidative phosphorylation.

NADH and FADH2 are oxidised in the elementary particles of mitochondria, where one proton and two electrons are formed from each molecule of NADH and are ejected into the inner membrane of mitochondria. These electrons are transferred from one acceptor to another which are arranged in a chain (The energy released is used for production of ATP).

These electrons and protons are finally transferred to oxygen to form water.

Know about a Scientist

Sir Hans Krebs previously been known for his excellent work on the urea science cycle in 1920's and 30's. Hans Krebs (1900 - 1981) received the Noble prize for working out the path way for oxidation of the 2 carbon acetyl group on acetyl Co A via a series of tricarboxylic intermediate. A cyclic pathway is now known as the Krebs Cycle, the Citric acid cycle and TCA Cycle.

Environment – Pollution

 The term pollution refers to the contamination of the environment- air, water and land- with harmful wasters resulted from human activities. Environmental pollution has become a major world wide problem. It has badly affected the whole biosphere.

Pollution has been caused by man. Man has been polluting the air with smoke and poisonous gases; rivers, lakes and oceans with sewage and harmful chemicals. During loading and unloading of crude petroleum in huge tankers million of tons of oil spill sin the oceans adversely affecting the aquatic life. You can observe the dead bodies of birds and fishes near sea shores or floating on the water.
Industries cause air pollution
 Increasing human population of the world and industrialization are the major causes of environmental pollution. The jungles have bee shaved off to accommodate the increasing population. This has considerably reduced the vegetation and forest cover over land. During the lost 50 years industries have multiplied manifold. The harmful chemical discharges of factories are polluting the rivers and oceans. The smoke produced by automobiles is increasing the air pollution and the noise produced by the engines of motor vehicles is aggravation the noise pollution. Modern means of agriculture have increased the use of pesticides which have also added to land and water pollution.
Industries cause water pollution
The marine life in the big lakes like Ari has vanished due to pollution. The sewage water, industrial wastes ad the water from agricultural farms containing extensive amount of fertilizes has filled his lake with too much of phosphates and nitrates. These chemicals have permanently distorted the biological balance of the lake. All the fishes of the lake have died. The water of Ganga and Yamuna Rivers is also becoming badly polluted. The Dal lake of Srinagar is in worse condition because of pollution. Pollution has affected mankind adversely. For the improvement of degradation of biosphere only man is responsible. And protection of flora and fauna also depends on the ways and means adopted by the human beings for their livelihood.