10th Class

       Depletion of Ozone Layer   Ozone is a molecule made up of 3 molecule of oxygen atoms combined together. It is also poisonous in nature. It is formed in the upper layer of the atmosphere by the action of ultraviolet radiation on oxygen gas. The high energy ultraviolet radiations from the Sun splits oxygen gas into free oxygen atoms. Since these oxygen atoms are very reactive, it get combine with oxygen molecules to form ozone molecules.     Thus, the layer of \[{{\mathbf{O}}_{3}}\] molecule formed in the upper atmosphere. This protect us from the harmful ultraviolet radiation, and is called ozone layer. These harmful ultraviolet radiation can cause skin cancer and can also damage our eyes by causing an eye diseases, called cataract. It also destroy our immune system. Hence we can say that more...

         The Transformation of Energy   The transformation of energy in an ecosystem begin first with the input of energy from the Sun. Energy from the Sun is captured by the process of photosynthesis. Carbon dioxide is combined with hydrogen, which is derived from the splitting of water molecules to produce carbohydrates. Energy is stored in the high energy bonds of adenosine triphosphate, or ATP. Because it is the first step in the production of energy for living things, it is called primary production. Herbivores obtain their energy by consuming plants or plant products, carnivores eat herbivores, and omnivores consumes both plants and animals. A simple food chain as shown in the figure given below, in which energy from the Sun, captured by plant photosynthesis, flows from trophic level to other trophic level via the food chain. A trophic level is composed more...

       Introduction   The total sum of all physical and biological conditions of a place, in which we are living, is called its environment. The physical condition includes; the temperature, pressure, light, soil, etc. and the biological conditions includes the plants, animals and microorganisms around it. Any change in one of these conditions can affect the organisms living in this environment. The energy in the environment comes from different sources and these energy can be used in different forms. We can convert one form of the energy to the another, depending on our requirement. The total energy during a physical and chemical changes remains the same, although it is converted from one form to the another.            Ecosystem An ecosystem is a biological environment consisting of all the organisms living in a particular area. more...

       Speciation   A species is the organisms consisting of similar individuals, which can breed together and produce fertile off springs. The species can be man or other animals or crops plants. Thus the process of developing new species from the existing species is known as speciation. Normally the new species arises due to the variation, which passed from one generation to the next and get accumulated over the long period of time. This also happens when the population of same species splits up into two separate groups, which then get isolated from each other geographically by the barriers such as mountain ranges, river or the sea. The main factors which could cause speciation are the geographical isolation, genetic drift caused by drastic changes in the frequencies of particular genes and the variations caused in individuals due to natural selection.    There more...

         Darwin’s Theory of Evolution    Darwin's gave the theory of evolution of species. According to his theory of evolution:

• Within a population there is natural variation of which some are positive and some are negative.
• The population remain constant even though all species produce large number of off springs.
• There is a continuous struggle for food, shelter and matting between the members of the same species.
• Only the individuals with favorable variations will survive and other will eliminate.
• The favorable variations are passed onto next generation.
• The variations accumulated over the long period leads to the evolution of new species.

  Another theory of evolution is the theory of natural selection. According to this theory only those traits are passed from one generation to the next which are favorable for the survival and reproduction of the organism. The other more...

       Evolution   There are millions of life forms on the earth. The different life forms on the earth is due to evolution of new species from preexisting species, and variations, which occur from one generation to the next. The evolution of new organism is also called organic evolution. Evolution also known as biological or organic evolution is the change over time in one or more inherited traits, found in populations of organisms over the time. Inherited traits are particular distinguishing characteristics, including anatomical, biochemical or behavioral characteristics, that are passed on from one generation to the next. Evolution may occur when there is variation of inherited traits within a population. The major sources of such variation are mutation, genetic recombination and gene flow. Evolution has led to the diversification of all living organisms from a common ancestor, which are described by Charles more...

       Sex Determination   Genetic inheritance determines the sex of an individual. The genes inherited from the parents determines the sex of the child, whether it is a boy or the girl. The sex chromosomes carries two types of genes X and Y. There are total number of 46 chromosomes in an individual; half of them comes from mother and half of them comes from father. Out of these 46 chromosomes, 44 are autosomes and 2 are sex chromosomes. In female the sex chromosomes are XX and in male the sex chromosomes are XY. During gametes formation the number of chromosomes is halved and is called haploid. It is 22 + X chromosomes from female and 22+X or Y chromosomes from male. If the X chromosomes of male fertilized with X chromosomes of female then the new born baby is female and if more...

         Mendel’s Law of Inheritance   The laws of inheritance of traits in human being are related to the facts that both the parents contribute equally to the child development. The traits of the child can be influenced by DNA both the parents and thus for each traits there are two versions in each child. On the basis of this Mendel's worked out the main rules of inheritance, known as Mendel's laws of inheritance. Gregog J Mendel was a botanist from Australia, who is known as the father of genetics. Mendel performed an experiment with the pea plant to study the variation pattern of inheritance of different characters. He choose pea plant because it is self pollinating, easy to cultivate and have distinct defined character. In his experiment, he crossed a variety of pea plant of different traits, such as tall and more...

       Heredity   The offspring reproduced by an organisms is similar to its parents in many respect. This similarity in the organism is due to the transmission of traits from one generation to the next. This transmission of traits form one generation to the next is called heredity. The study of the mode of transmission of traits from parents to their off springs is called genetics. It is actually the gene stretches of DNA which contains the coded information of the parents responsible for transmission of characters. Genes are the basic unit or the functional unit of heredity. The genetic constitution of an individual organisms is called genotype, which determines the physical characteristics of an individual. The outer environment also affects the variation in an individual. This also leads to the development of new traits in an individual and are visible in the more...

       Introduction   We know that all the organisms are the results of reproduction. A recognizable feature of a human being like height, complexion, shape and size are called traits. The transmission of characters from one generation to the next is called heredity. In sexual reproduction, both male and female are involved. The new offspring evolves with similar characteristic as of their parents. These characteristic are carried with the help of gametes presents in male and female parents. Although there is similarity between parents and offspring, but the similarity is not present in all respect. The new offspring is not the true copy of the parents. No two individuals are alike in all respect in this world. This difference which arises in the off springs from one generation to the next is called variation. The variation is produced during both sexual reproduction and more...