Effect of Pollution and its Control

Air Pollution Dry air has 78% N2, 21% O2, 0.03% CO2 and the rest other gases are about 1%. Air pollution is principally caused by man. Due to human activities, the amount of solid waste or concentration of gases other than O2 increase in the air and disturb the natural composition of air. This phenomenon is referred to as air pollution. Air pollution is one of the most dangerous and common kind of environmental pollution that is reported in most industrial towns and metropolitans. Motor vehicles are the major problems of the world...

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Shirish 11:37 PM   No comment

Mountains and Nepal

Mountain is a topographical feature that rises more than 300m above the surrounding. There is a difference between mountain and hill. Hill is a land surface lower than a mountain that rises prominently above the surrounding lands to elevations less than 300 m. This region is represented by Siwalik and Mahabharat range in Nepal. Mountain environment is of great importance in Nepal. Nepal is predominantly a mountainous country. The Himalaya extends over a length of approximately 2400 km from the Indus to the Brahmputra. The central sector of Himalaya about 800 km lies...

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Shirish 11:21 PM   No comment

Frog (Rana tigrina)

Frog is an amphibian, living both on land and in water. The amphibians are the first group among the chordates that live outside water. But the amphibian is still chained to water, in water it is born, to water it must periodically return for respiration. They are cold-blooded vertebrates having two pairs of limbs- tetrapods. They have smooth and moist skin. Rana tigrina is studied in detail because of its easy availability and its structural details have very common features to other animals. Classification: Phylum: Chordata Subphylum: Gnathostomata Superclass: Tetrapoda Class: Amphibia Order:...

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Shirish 5:08 AM   4 comments

Plasmodium ( The Malarial Parasite)

Plasmodium is the best known protozoan parasite of man, which causes malaria. malaria is one of the widespread tropical diseases among human being. About one-third of the entire population of many hot countries suffer from it every year. It is a serious economic and social problem as it causes deaths and affects majority of population. It is responsible for persistent sickness, loss of working ability and slowing down of mental and physical development among children. In 1943, Russel estimated that there were three hundred million cases of malaria in the world. In 1957...

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Shirish 10:27 PM   No comment

Functional Aspects of Ecosystem

The functional aspects of ecosystem include the flow of energy and the cycling of nutrients. Inorganic compounds are synthesized into organic structure by the green plants through photosynthesis and solar energy is utilized in this process. Energy enters the ecosystem, when the producers build organic compounds during photosynthesis. The green plants (producers) fix solar energy and with the help of inorganic substances such as carbon dioxide and water taken from soil and aerial environment they build up complex organic matter. The organic matters are carbohydrate, fat, protein, etc. From green plants these organic...

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Shirish 1:44 AM   1 comment

Factors of Ecosystem [Part 2]

Topographic Factors (Physiographic Factors): Topographic factors include height, direction and the steepness of slope.1) Height or Altitude: Higher altitude (mountains, hills, etc.) is characterised by low temperature, high velocity of wind, lower atmospheric pressure, high humidity and rainfall. The temperature decreases with the increase of height and the lower temperature favour the formation of clouds and rain. Thus, the mountains and hills are favourable for plant growth and causes different types of forest due to above climatic variations. However, at very high hills and mountains the water vapours directly condense into snow and...

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Shirish 11:47 PM   No comment

Factors of Ecosystem [Part 1]

Every living organism is surrounded by materials and forces which constitutes its environment and from which it must derive its needs. Any external force, substance or condition which surrounds and affects the life of an organism in any way is referred to as environmental factor or ecological factor. These factors are living as well as non-living. The living factor is called the biotic factor and non-living is called the abiotic factor. Thus, the ecosystem is governed by two environmental factors (components) biotic factors and abiotic factors. These factors determine the quality and the...

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Shirish 3:11 AM   No comment

Reproductive System of Earthworm

Earthworms reproduce sexually. They cannot reproduce asexually. They are hermaphrodite (monoecious) i.e. both ovaries and testes are found in the same individual. They are protandrous, the male sex cells mature much earlier than the female cells, therefore, self-fertilization is not possible. The relative position of ovary and testes also makes self-fertilization impossible. Cross-fertilization is preceded by copulation and cocoon formation. Male Reproductive Organs: The male reproductive organ comprises testes, testis sacs, seminal vesicle, vasa deferentia, Prostate gland and accessory glands. Testes: The earthworm contains two pairs of testes, one pair in the 10th...

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Shirish 2:12 AM   2 comments

Earthworm [Part 2]

5) Locomotion: Locomotion in earthworm is caused by setae and the musculature of the body wall. When as earthworm starts to crawl, the first few segments become thinner and extend forward. This is due to contraction of the circular muscle fibres and relaxation of the longitudinal muscles in that region. The longitudinal muscles of the anterior segments now contract and the circular muscles relaxes due to which anterior end becomes shorter and thicker. The seta of these segments then protrude out and get gripped into the soil. The contraction of anterior segments pull...

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Shirish 9:13 PM   2 comments

Earthworm [Part 1]

The name earthworm is given to the annelid worms, because they live and burrow in the ground. Annelids are triploblastic, bilaterally symmetrical and coelomate animals. The presence of true segmentation (metamerically segmented) in their body is a diagnostic feature of these animals. The locomotary organs are setae or chaetae present in each segment. Phylum Annelida, also sometimes known as Annulata, contains elongated, vermiform and true segmented animals. ...

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Shirish 8:15 PM   2 comments

Human Evolution

Like any other species human also evolved over millions of years. The early stages of human evolution are studied by means of the comparative anatomy of fossils and the evidence of thee comparative biochemistry of present-day humans and other mammalian species. Humans belong to an order of class mammals called Primates. The present day order primates consists of two suborders: Prosimii, includes tree-shrews, lemurs, loris, tarsiers etc. and Anthropoidea, includes monkeys, apes and humans. Humans belong to the family Hominidae. ...

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Shirish 7:01 AM   No comment

Evidences of Evolution

The doctrine of organic evolution is supported by following evidences:1. Structural evidence: The most extensive evidence in support of evolution comes from the study of structural similarities. Related groups of organisms possess homologous structure because of common ancestry. Among the vertebrates from the frog to man, the vertebral column, eyes, ears, brain and the digestive system are constructed on the same basic plan. Some homologous structures suggest a common ancestry. In plants, the structural similarities of roots, stems, leaves, flowers show the evolutionary tendencies of plants. Morphological similarities in the type of venation,...

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Shirish 10:36 PM   2 comments

Origin and Evolution of Life

Origin of Life:The ability to grow and produce new forms distinguishes living organisms fron non-living objects. The origin of life on Earth is a most complicated problem for thinkers, philosophers and naturalists from ancient time. Different views have been put forward concerning the origin of life by workers of different ages. some of the most important hypothesis and theories regarding the origin of life are as follows:Origin of Earth and its Atmosphere: The earth was probably originated 4600 million years ago. The sun and the planets were formed together from a spherical cloud...

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Shirish 10:36 PM   1 comment

Structure of Cell [Part 3]

Plastids: Plastids are cytoplasmic organelles about 5 micron in diameter and 3 micron in thickness, found freely in cytoplasm of the most of plant cell. they are not found in animal cell. the term plastid was first used by Schimper (1885). They are usually disc shaped and arise from small granular bofies, the protoplastids. Based on the types of pigments, three types of plastids are recognized: leucoplast, chloroplast and chromoplast. One form of plastid can change into another form, for example, in tomatoes the ovary contains leucoplasts which change into chloroplasts in young...

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Shirish 12:25 AM   No comment

Structure of Cell [Part 2]

Cytoplasmic Organelles:Ribosome : The ribosomes were first reported in plant cells by Robinson and Brown (1953) and Palage (1995). They observed itin animal cell, usually attached to the outer surface of endoplasmic reticulum. The name ribosome was proposed by Haguenau (1958). It is a minute rounded ribonucleoprotein structure, consisting of RNA and proteins. the ribosome contains two unequal subunits and these subunits remain attahed together by means of binding force of magnesium atom. The larger subunit has dome like shape, while the smaller subunit occurs above the larger subunit as a cap like...

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Shirish 1:51 AM   No comment

Structure of Cell [Part 1]

Before discussing about the structure of cell, lets have a brief introduction of cell in terms of its structure. Cell is a microscopic protoplasm surrounded by the cell membrane. The protoplasm consists of the cytoplasm and the nucleus. In a plant cell, the cell membrane forms the outermost covering of the cytoplasm beneath the cell wall. The cytoplasm contains several living organelles and non-living inclusions. A cell under a microscope shows the following: Cell Size:An average cell varies from 0.01mm to 0.1mm in diameter. The cell of Acetabularia, an unicellular algae is about...

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Shirish 4:29 AM   No comment

Cell Biology

So what is Cell? Cell is the basic structural and functional unit of living organism. It consists of microscopic mass of protoplasm surrounded by a cell membrane. it is the smallest unit, that can perform all the processes of life. In a unicellular organism, the single cell performs all metabolic functions such as growth, respiration, reproduction, digestion, excretion, etc. In multicellular organisms all the vital activities are the result of combined action of these cells. Hence, the cell is considered as basic unit of life. Robert Hooke(1635-1703) dicovered cell in 1665. ...

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Shirish 2:10 AM   No comment