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 ozone layer is very useful to us and is also very essential for the earth's life forms. In recent past it has been found that the ozone layer is depleting and hole has appeared in the polar region of the ozone layer, which is a matter of great concern. The main reason for the depletion of ozone layer is the release of chlorofluorocarbon (CFC). This CFC is widely used in refrigerator and other coolants and this CFC reacts with ozone layer and gradually destroy it and thus leading to its depletion.
Identify the biodegradable waste among the following:
(a) D. D. T.
(b) Plastic
(c) Glass
(d) Jute
(e) None of these
Answer: (d)
There are two components of ecosystem, one is biotic and other is abiotic. Which one among the following is a biotic component of the ecosystem?
(a) Air
(b) Plant
(c Water
(d) Land
(e) None of these
Answer: (b)
Which one of the following is not a terrestrial ecosystem?
(a) Forest
(b) Desert
(c) Grass Land
(d) River
(e) None of these
Answer: (d)
There are some organisms which manufacture their own food using simple inorganic substance and sunlight. Identify the organism among the following which does this work?
(a) Blue Green Algae
(b) Goat
(c) Bacteria
(d) Virus
(e) None of these
Answer: (a)
Which one among the following is a lotic ecosystem?
(a) Pond
(b) Swamp
(c) River
(d) Land
(e) None of these
Answer: (d)
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 of organisms that make a living in the same way, that is, they are all primary producers, primary consumers or secondary consumers.
Dead tissue and waste products are produced at all levels. Scavengers, detritivores, and decomposers collectively account for the use of all such "waste" — consumers of carcasses and fallen leaves may be other animals, such as crows and beetles, but ultimately it is the microbes that finish the job of decomposition. Usually when we think of food chains we visualize green plants, herbivores, and so on. These are referred to as grazer food chains, because living plants are directly consumed. In many circumstances the principal energy input is not green plants but dead organic matter. These are called detritus food chains. Examples include the forest floor or a woodland stream in a forested area, a salt marsh, and most obviously, the ocean floor in very deep areas where all sunlight is extinguished 1000's of meters above.
Food Chain
All the living organism obtained its energy form the food they eat. The food transfer energy from one organism to the another. The sequence of living organism in a community, in which one organism consumes another organism to transfer food energy, is called food chain. The food chain tells us that the plants are the starting point of every food chain. There are number of food chains in our ecosystem. In our food chain grass are the producer which uses solar energy to prepare food for themselves and this grass is consumed by the consumers such as deers and other animals.
Food Web
There are large number of food chains in a ecosystem and many food chains are interconnected by species, present in more than one food chain. Thus, the network of food chain is called food web. The food web has many intercrosses and 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. It also includes all the nonliving, physical components of the environment with which the organisms interact, such as air, soil, water and sunlight. The entire array of organisms inhabiting a particular ecosystem is called a community. In a typical ecosystem, plants and other photosynthetic organisms are the producers that provide the food. Ecosystems can be permanent or temporary. Ecosystems usually form a number of food webs. They are functional units consisting of living things in a given area, nonliving chemical and physical factors of their environment, linked together through nutrient cycle and energy flow. The different types of ecosystems are:
Biomes
Biomes are a classification of globally similar areas, including ecosystems, such as ecological communities of plants and animals, soil organisms and climatic conditions. Biomes are defined on the basis of the factors, such as trees, shrubs and grasses; leaf types i.e. broadleaf and need leaf, plant spacing forest, woodland, savanna and climate. Unlike ecozones, biomes are hot defined by genetic, taxonomic or historical similarities. Biomes are often identified with particular patterns of ecological succession and climax vegetation.
A fundamental classification of biomes is:
Components of an Ecosystem
We have learned about the parts of an ecosystem, climate and soils previously. From this we can have a basic understanding of the diversity of plants and animals, and how plants and animals and microbes obtain water, nutrients, and food. We can classify the organisms into two parts as biotic components and abiotic components. The biotic components include plants, animals and microorganisms; whereas the abiotic components include temperature, light, land, water, sunlight etc. Usually, biological communities include the 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 is no real progress in the field of evolution, rather it is just the production of diversity of life forms and shaping of this diversity by the environmental selection. The only progress in the evolution which appears to us is that the organism with more and more complex body designs have emerged over the ages. It is not that with the appearance of organisms with complex body designs the simpler organisms will disappear. It depends on the environmental condition of the place. For example, one the simplest and primitive life forms called bacteria still inhibits in some of the most inhospitable habitats such as hot springs, deep sea, thermal vents and the ice in Antarctica.
Which one of the following sex chromosomes give rise to the male child?
(a) XX
(b) XY
(c) YY
(d) XYX
(e) None of these
Answer: (b)
Name the scientist who gave the theory of evolution.
(a) Darwin
(b) Lamarck
(c) Mendel
(d) Baptiste Pierre
(e) None of these
Answer: (a)
Which one of the following is not present in the darwins theory of evolution?
(a) Overpopulation
(b) Natural Variation
(c) Struggle for Existence
(d) Use and disuse of organ
(e) None of these
Answer: (d)
Which one of the following is more in common with us in terms of evolution?
(a) Chinese Boy
(b) Monkey
(c) A chimpanzee
(d) Bacteria
(e) None of these
Answer: (c)
Darwin’s Theory of Evolution
Darwin's gave the theory of evolution of species. According to his theory of evolution:
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 Darwin as endless, forms most beautiful, and most wonderful.
There are four common mechanisms of evolution. The first mechanism is natural selection; a process in which there is differential survival and/or reproduction of organisms that differ in one or more inherited traits.
Homologous Organ
The organs having same basic structure but different functions are called homologous organ. The homologous organ provides the evidence for evolution. For example, the forelimb of a man, a lizard, frog, bat etc have same basic structure but different functions.
The forelimb of man helps in holding, forelimb of lizard helps in running, forelimbs of frog helps in prop up. The forelimb of bird and bat helps in flying from one place to another.
Analogous Organ
The organs having different body structure but same functions and similar appearence are called analogous organ. 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 the Y chromosomes of male combines with the X chromosomes of female then the new born baby is male.
Acquired and Inherited Traits
Acquired Traits
We know that new species arise from pre existing species with modifications. The favorable changes appear due to the use or disuse of organs, over a long period of time. The traits which develop in an organism due to external environment is called acquired traits. The acquired traits of an organism cannot be passed on to their future generations. Only those traits can be transmitted from one generation to the next, in which, changes have occurred in the genes present in the reproductive cells of parents. The changes which occur in non reproductive cells of an organism cannot be inherited from one generation to the next,
Inherited Traits
The traits which are transmitted from one generation to the next, due to the change in its gens, is called inherited traits. For example, the colour of red beetles changes from red to green during reproduction. This change of colour in the beetles has been due to change in the genes of the reproductive cell.
The transmission of traits from one generation to the next is called:
(a) Variations
(b) Characters
(c) Heredity
(d) All of these
(e) None of these
Answer: (c)
Which factor determines the appearances of an organisms:
(a) Chromosomes
(b) Genes
(c) DNA
(d) Ribosomes
(e) None of these
Answer: (b)
Which plant did Mendel's chose for his experiment to study the 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 dwarf plants, round and wrinkled seeds, white and pink flowers etc. These two plants are called parental generation and the generation that was produced by crossing these two plants was called the first generation (F1). When the plants of F generation were crossed among themselves followed the generation called second generation (F2).
Mendel gave the following conclusion from his experiment:
When the traits of \[{{F}_{1}}\] were crossed among themselves, the 75% of plants in \[{{F}_{2}}\] generation were tall and 25% of them were dwarf. Thus, the phenotype ratio was 3:1.
After performing the experiments on the inheritance of traits of one character he performed an experiment with the two character or dihybrid cross. He crossed the plants of round and yellow seeds with the plants of wrinkled and green seeds: and found that all the plants \[{{F}_{1}}\] generation are round and yellow. When the plants of \[{{F}_{1}}\] generation were crossed among themselves he found that it gave rise to four types of seeds. Of these 301 were round and yellow, 102 were round and green, 96 were wrinkled and yellow and 30 were wrinkled and green. Hence their phenotype ratio was about 9:3:3:1.
The genotypic ratio of the dihybrid cross is found to be 1:2:2:4:1:2:1:2:1. He found that it was actually the gene which were responsible for the traits of an organisms. These traits are presents on the chromosomes of the genes of an organisms. It is the dominant gene which shows it character in the physical appearance of an organisms. 
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 physical appearance, which is called its phenotype.
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 asexual reproduction. Though the variation in case of asexual reproduction is minimum, but still it is there. If we observe the mango plants/they all appears to be similar, but there is difference in the taste of mangoes of different plants, there is difference in their size etc. The variation is essential for organic evolution. The evolution of new species is only due to the variation in the organisms.
Accumulation of variation
We know that reproduction results in variation from one generation to the next. The variation produced in the organisms during the successive generation gets accumulated over a long period of time in an organism. After several generation these variations comes up in the organisms and the organisms starts showing up different characteristics and hence leads to the appearance of new species. The main advantage of variation in a species is that it increases the chance of its survival in a changing environment. The organisms which shows positive variation, survives. Those who do not shows variations get extinct.
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