What is Atmosphere? Describe the Composition of Atmosphere.

 

Atmosphere is the gaseous mantle around the lithosphere and hydrosphere. It constitutes a number of gases such as nitrogen, oxygen, argon, carbon dioxide, neon, xenon, ozone, and knyton. These gases have definite percentage in the atmosphere in normal conditions. In addition to this, atmosphere also includes water vapours, dust particles, industrial gases, pollen, and several other micro-organisms carried particles.

Lithosphere is mainly made up of the solid components and constitute rocky substance. Hydrosphere includes the liquid components such as lakes water, water, ocean and ponds.

These three subdivisions of the environment are the main sources of energy for plants and animals. They affect the metabolism in various ways. The atmosphere provides various gases like oxygen, nitrogen, carbon dioxide, lithosphere provides all minerals and hydrosphere provides water.

The global environment consists of three main subdivisions:
(i) Hydrosphere (ii) Lithosphere (iii) Atmosphere

The hydrosphere includes all liquid components, i.e. , water in oceans, lakes, rivers, etc.

The lithosphere comprises the solid components, i.e. , the rocky substances of the continents.

The atmosphere is the gaseous mantle which envelops the hydrosphere and the lithosphere.

Living organisms require inorganic metabikutes from each of these sub-divisions. The hydrosphere supplies liquid water, the lithosphere supplies all other minerals, and the atmosphere supplies oxygen, nitrogen and carbon dioxide.

Together, these inorganic materials provide all the chemical elements needed in the construction and maintenance of living matter. In addition to being source of supply, the three sub-divisions of the environment also affect metabolism in various other specific ways.

The Hydrosphere: Water is the most abundant minerals of the planet. It covers about 73 percent of the earth’s surface and it is the major constitute of lithosphere and the atmosphere. Water is also the most abundant component of living matter and therefore it is the major inorganic nutrient required by all living organisms. In metabolism, water is the exclusive source of the element hydrogen and one of the several sources of oxygen. The basic water cycle which moves and conserves water in the environments is quite familiar.

Solar energy evaporates water from the hydrosphere into the atmosphere. The vapours thus produced are cooled and condensed at higher altitudes, produce clouds, and precipitation as rain or snow then return the water to the hydrosphere. This is the most massive process of any kind of earth, consuming more energy, moving more material than any other.

(1) In using water as metabolic raw material, organisms withdraw it principally from the hydrosphere. Aquatic organisms absorb water directly from their liquid environment; they excrete some of it back while they live and after death, the remainder, still in the form of liquid water, is returned through decay. Terrestrial organisms absorb liquid water from the reservoir present in the soil and in bodies of fresh water. Plants and animals move such water through their bodies and in the process they retain required quantities.

(2) Water influences metabolism not only through its function as a prime nutrient but also through its effect on almost all aspects of climate and weather, both in the sea and on land. In the ocean, water warmed in the tropics becomes light and rises to the surface, whereas cool polar water sinks. These up-down displacements bring about massive horizontal shifts of water between equator and pole. The rotation of the earth introduces east- west displacements. These effects, reinforced substantially by similar patterned wind-producing air-movements, result in oceanic currents. The latter influence climatic condition not only within the seas, but also in the air and on land.

(3) Climatic effect is a result of the thermal properties of water. Of all liquids, water is one of the slowest to heat or, cool, and it stores a very large amount of thermal energy. The oceans thus become huge reservoir of solar heat. The result is that sea air-chilled by night, becomes less cold because of heat radiation from water warmed by day. Similarly, sea air-warmed by day becomes less hot because of heat absorption by water cooled by night. Warm or cool onshore winds then moderate the inland climate in daily patterns. More profound effects are produced by heat radiation and absorption in seasonal summers and winter patterns.

(4) Global climate over long periods of time is determined by the relative amount of water locked into polar ice. As the polar ice is melting, water levels are now rising and coast lines are gradually being submerged. If trend during the past 50 years are reliable indications, the earth appears to be warming up generally. Deserts are presently expanding, snowlines on mountains are receding to higher altitudes; in given localities, more days of the year are snow free; and the flora and fauna native to given latitudes are slowly spreading poleward. It is difficult to be sure whether these changes are merely part of a short warm cycle or are really indicative of a long-range trend.

All these various cyclic changes in the hydrosphere have profound impact on metabolisms.

The Lithosphere : This sub-division of the environment plays two vital roles in metabolism:
(a) It is the exclusive source of most mineral metabolites for all organisms, terrestrial as well as aquatic; and
(b) It forms the bulk component of soil, required specifically by terrestrial plants.

Minerals and Cycles: Like the world’s water, the rocky substance of the earth’s surface moves in a huge cycle, but here the rate of movement of cycle is measured in thousand and millions of cycle. One segment of this mineral cycle is diastrophism that is the vertical uprising of the large tracts of his earth crust. Large number of the parts of the continent or the whole continent may undergo such diastrophic movements. These movements may occur when a land mass is pushed up from below. The changes thus occur are very slow. The important instance of diastrophism is mountain building. The youngest and highest mountain ranges are the Himalayas, the Rockies, the Andes, and the Alps. All these were uplifted some 75 million years ago and we may still now note that the earth’s crust in these regions is not completely settled.

This type of uplifting of the mountains, or formation of mountains has long lasting effect on climate, and consequently on the metabolism.

Segment of the global lithospheric cycle involves gradation that is the lowering of high land and the levelling of mountains. These changes are brought about in past by actual geologic sinking of land and in part by the action of the hydrosphere and the atmosphere. These actions usually take the form of erosin and dissolution of rock. There are many instances of erosional processes.

Accompanying the physical forces of gradation are chemical forces which are of particular importance.
1. There are the chemical action of water and chemical processes which accompany the major erosional factors. They contribute to breaking large stones into smaller ones and small pebbles into tiny sand grains and microscopic rock fragments.
2. Whenever water is in contact with rock, it dissolves small quantities of it and thus acquires a mineral content. The dissolved minerals are carried largely in the form of ions.

The dissolved soil minerals ultimately drain back into the ocean. It was partly by this means that the earlier seas on earth acquired their original saltiness, and as the global water cycle now continues, it makes the oceans even saltier. The mineral icons in the ocean are used freely by the organism as metabolites.

The lithospheric cycle supplies many more types of minerals than organism normally require. Those withdrawn and used by most organisms include, e.g., ions of nitrates, chlorides, carbonates, sulphates, and ions of sodium, potassium, managanese, copper and iron.

Soil: We have thus noted that lithosphere plays a special role in the metabolism of land plants in that contributes importantly to the formation of soil. This complex material serves in plant maintenance in two-ways:
(a) It provides mechanical anchorage for plants.
(b) It holds water and mineral ions, the source from which land plants obtain supplies of these inorganic nutrients.

The major components of soil was contributed by living organisms. Early terrestrial organisms which did not require soil themselves shed their excretion products into the sand layers, and upon death their bodies came to be added as well.

One of the main reasons why such a vast host of animals has colonized the soil is because it provides an insurance against the danger of desiccation. Few soil species can live above ground for long and those that do so have to adopt some means of protecting themselves during dry weather. It is significant that sandy soils never support as many animals as those containing a high proportion of humus and some clay. Thus water content of a soil and the amount of organic matter present, together provide a reliable index for predicting the density of animal colonization. The upper layer of the soil is generally referred to as topsoil. The roots of the small plants are embedded entirely in topsoil. The chemical value of a soil depends upon its usable water and mineral content. Soil particles are enveloped by thin films and water.

Explain the four Zones of Atmosphere?

Atmosphere can be roughly divided into four zones.

(1) Troposphere : It is about 20 km above the earth surface. In these important events such as cloud formation, lightning thunder storms and thundering all take place in this sphere:

(2) Ionosphere : The rest above the mesosphere upto height of 400 kms above the earth’s surface is ionosphere. Most of the gases are present in the form of ions.

(3) Stratosphere : It is next to troposphere. It is about 30 kms above the troposphere, is called as stratosphere. In this zone ozone formation takes place, under the influence of ultra violet component of sunlight.

(4)Mesosphere : About 40 km in height above stratosphere is called mesosphere. In this zone temperature shows again a decrease upto 80°C.

What is Environment ? Explain the Biotic and Abiotic Factors of Environment ?

Environment: The distribution of plants and animals is not haphazard. The differences in the vegetation and species of different places are mainly due to the difference in the environment. Plants and animals do not live in a vacuum. They stand or walk upon the earth, drift or swim in the water or float or fly in the air. Everything about them is their environment. Closely related to the concept of environment is habitat by which is meant the particular place or situation in which a plant or animal lives or grows. Habitat is more specific in meaning than environment as a whole.

Broad aspects of the landscape such as water, soil, desert or mountain, the physical influences such as moisture, temperature and light, and the total living population of any area, i.e. interdependent animals and plants, constitute the environment. The totality of the physical environment is called an ECOSYSTEM and the total world of life is called as biosphere. Every organism within the biosphere affects the life of every other, directly or otherwise. Man, for examples cannot continue to live without the bacteria in the soil, the green plants on the land and in the sea, and even the scavengers of the dead. And what man does to the environment matters greatly to all other living organisms around him.

Environmental factors fall into two categories
(1) Physical or abiotic (non living) and
(2) Living or biotic factors

Biotic Factors of Environment

The plants and animals live together and influence each other’s life and also modify the environment. In fact, living organisms are most potent factors in the growth and development of each other. Some biotic influences, such as pollution, dissemination of fruits and seeds, grazing browsing, parasitism, symbiosis etc. are direct. The other influences like burrowing of soil by worms and rodents, decay of the dead organic matters by soil organisms etc. are indirect.

Plants compete with one another for light, water and mineral supply. Large trees change the underneath climate. It is more moist, moderately warm but receives less light. As a result, forests have many layers of plants with different height (stratification). In moist tropics many woody lianas climb up the tree trunks for exposing their foliage to the sunlight and interfere in normal photosynthesis of the trees. They may deform or even kill the tree. Parasitic plants rob host plants of nutrition and may also cause diseases. Some plants growing in nitrogen deficient areas (i.e. insectivorous plants) trap insects to obtain supply of nitrogen. Certain fungi assist higher plants in obtaining water and minerals in return for food and water. Certain bacteria and cyanobacteria fix atmospheric nitrogen, thus, improve the fertility of soil.

Only some perennial grasses can withstand both excessive grazing and trampling. Trampled soil become compact and does not contain much air and water. Many insects and other animals help in pollination and dissemination of fruits and seeds in the plants. Earthworms and other burrowing animals improve the aeration of the soil and bring fertile soil over the surface. Animal excreta is an important source of organic matter to the soil. The super animal, the man has also been changing the flora and fauna by introducing new plants and animals. Fires are often man made. They destroy vegetation and volatilize the minerals, present in the soil.

Abiotic Factors of Environment

Of the many physical factors affecting living organisms, only few will be considered. Some factors are most important than others; and organisms vary with respect in now much they are controlled or limited by the various physical factors.

Substratum : The earth, water, and the air, or the bodies of other plants and animals upon which organisms live, constitute a surface or a medium and may be given the general title of “substratum”.

Animals may have structural adaptations to the particular substratum on which they live. The streamline form of fish, seals, and whales, the flattened body of lice, the long legs of the wading bird, the sharp claws that enable squirrels to run up the trunks of trees, the well protected hoofs of horses, pigs camels and zebras, the hooks that enable the tapeworm to cling to the intestinal walls instead of being out with the moving stream of intestinal contents : all are successful adaptations to a variety of type of substratum.

While some organisms have become structurally adapted to their substratum, other have changed the substratum to fit themselves. Examples are the nests of the ants, the tubes of many marine annelids, and most obvious of all the streets, ‘bridges, tunnels, airplanes, buildings, and homes of man.

Substratum may be a limiting factor. An organism that has become well adapted to a specific type of substratum is limited in its distribution by the availability of that substratum. It is true, however, that organisms live in an environment where many factors are acting. It is most frequently true that animals and plants are limited not by a single but by a whole complex of factors.

Temperature: Most living organisms can survive only in a narrow range of temperature (59 35°C). However, there are notable exceptions to it. Certain bacteria, cyanobacteria (blue green algae), seeds, spores and encysted protozoans can occur in hot springs (60°C)  — 90°C) or ice (30°C to 50°C).At high temperature, most organisms are killed due to denaturation of enzymes. Very low temperature also kills the organisms by freezing their body fluid. Therefore many organisms have developed physiological and behavioral adaptations to avoid extremes of temperature. For example:

(i) Some animals can live in extremely cold regions (e.g. polar bear). They hide and undergo hibernation (winter sleep) in frost free shelters such as caves, burrows etc. during winter. Some animals undergo aestivation (summer sleep) in hot and dry season.

(ii) Some birds and animals migrate to warmer places in winter to avoid extreme cold.

(iii) Many desert animals live in deep burrows to avoid the intense heat of the desert. They become active only at night (nocturnal), early morning (auroral) or evening (vesperal).

(iv) Plants also have adaptation for protection against extremes of temperature. These include development of thick cuticle, corky bar, dense hairy coat, thick leaves, mucilage, high solute content etc.

Temperature varies in various quarters of the earth according to latitude and altitude. It is also influenced by plant cover, atmospheric humidity, water reservoirs, air current and snow. According to the change of temperature with the increase of latitude, various vegetation zones have been recognized. Similarly, on the basis of change in temperature due to altitude, many vegetation zones can be observed. Changes in both, the latitude and the altitude, show more or less similar effect upon the type of major vegetations of the world.

Light: Light may be a limiting factor. The penetration of light into the ocean determines the depth at which green plants may grow. Since CO2, H2O and salts are present in abundance, light is the most important factor. Algae are the most abundant at the surface of the sea and decrease with increasing depth until at 200 feet the plant life is very sparse. And since less than 0.1 % of the light reaches below 600 feet, green plants are absent from the ocean depths of course, the absence of the plant means that animals that depend directly upon plants for their food supply are also absent. Only carnivores and scavengers live on the ocean bottom, and these feed on each other and on organic stuff which settles out from above.

Light affects animals indirectly though the fact that animals depend upon plants for their food. Light also affects animals in variety of other mechanisms. Exposure to ultra-violet radiation enables some animals to manufacture vitamin D. Light affects animals directly as they perceive their prey or detect their enemies through sense of light. Light sensitive organs are present in nearly all animal groups from the protozoans to the highest forms. Many animals have evolved structures or forms which enable them to escape detection by their enemies which hunt by means of sight. Examples are the walking — stick insect, the dead — leaf butterfly, and the various colour patterns on insects, birds, snakes and mammals.

Precipitation : It occurs in the form of rain, dew, hail or snow. Rain is the major source of water to the• earth. The water retained in the soil depends on a number of factors, such as soil constitution, steepness of the slope and the periodicity of the rain. Seasonal distribution and the total rainfall determine the type of vegetation in an area. Areas with heavy rainfall support luxuriant vegetation and abundant animal life. Scanty rainfalls support sparse xerophytic vegetation and scarce animal life. Rainfall; throughout the year produces tropical evergreen forests. Good rainfall, which occurs in one or two seasons produces deciduous forests. Moderate rainfall occurring in 1- 2 seasons produces grasslands, while low seasonal rainfall gives rise to deserts. Dew is a very good source of water to shallow rooted plants of arid area. Hail occurs in the form of ice balls and causes mechanical injury to the plants. Snowfall occurs in the cold regions. Duration of snowfall determines the type of vegetation. In arcaic and alpine regions, trees are absent. Only shrubs, herbs, mosses and lichens can grow because of snowfall.

Water: Most aquatic animals cannot live without a large supply of constantly renewed water. Such are most fish and other truly aquatic forms, whose respiration is adjusted for utilizing oxygen dissolved in water. These must live in large bodies of water or in swift streams. But certain aquatic types like lungfish, Salamanders, and crayfish survive temporarily drying by burrowing into the damp mud. Frogs spend much of their adult lives on land but cannot live very far away from the water, to which they must return to lay their eggs.

The reptiles are the first vertebrates to have evolved forward eliminating water as a limiting factor in their distribution. They lay land eggs and have a heavy scaly skin through which water cannot escape. Some reptiles (turtles and crocodiles) have secondarily returned to the water, but the reptile group as a whole achieved its early success through adaptations to lack of water, and the group now has a large number of the most successfully adapted desert animals. Like the desert animals, plants which live on a low- water economy have a relatively low metabolic rate, inspite of the high temperature. In the desert, however, although sunlight, C02, 02, soil minerals, and all other factors are present in abundance, water acts as a limiting factor in excluding most plants and in determining the extremely wide spacing of those plants able to survive the arid conditions.

Humidity : Humidity refers to the amount of water vapour present in the atmosphere. It controls the formation of clouds, dew, fog etc. It directly regulates the rate of water loss from the body surfaces of plants and land animals by transpiration and perspiration, respectively. In arid areas, low humidity increases water loss. Therefore, both plants and animals develop modification to reduce water loss in such areas. The high humidity decreases transpiration and therefore, more water becomes available for metabolism. This result in the production of luxuriant growth as is found in tropical rain forests. Epiphytic plants like orchids grow only in areas with high humidity such as tropical rain forests, because they get their water supply directly from air. Stratification or distribution of plants in the different strata in the forest is also controlled by the humidity in the different layers of the atmosphere. The plants which require the least atmospheric humidity grow into tall trees while those requiring high humidity constitute the ground flora.

Wind : The wind is a powerful agent influencing the growth and distribution of many organisms. Drying action of high, warm winds creates physiological draught. The wind removes humid air about the leaves and increases transpiration and ultimately the foliage turns brown. Strong and persistent winds blowing from a constant direction bend the branches of trees. Hurricanes and other violent windstorms sweeping over forested areas may uproot and break the trees. The hurricanes and strong storms cause deaths among animals also, and often carry individuals far from their normal environment and set them down elsewhere. Winds are an important means of dispersal for seeds and small animals such as spiders, mites, and even snails.

Soil: The soil is a radically different environment for life than the one above the surface, yet the essential requirements do not differ. Like animals that live outside the soil, soil fauna require living space, oxygen, food and water.

Soil may be defined as mineral material that may exist in solid or unbroken form, such as boulders, gravels, large outcrops, solid sills of stones, or as finely divided particles of mineral matter referred to as sands, silts, or clays, depending upon the texture.

The texture of a soil is determined by particle size and the proportional amount of these sized particles within any one soil sample. Particle size is determined by the diameter of individual soil fragments. According to the international system of soil classification, soil particles with a diameter larger than 2.0 mm are gravel soils, those with diameter ranging from 0.02 mm to 2.0 mm are sands, soil particles with diameter of 0.002 to 0.02 mm are silts. The finest textured soils, with particle diameter of less than 0.002 mm are CLAYS.

To the soil fauna the soil in general possesses several outstanding characteristics as a medium of life. It is relatively stable, both chemically and structurally. The atmosphere remains saturated, unit soil moisture drops below a critical point. The soil affords a refuge from high and low extremes in temperature, wind, evaporation, light and dryness. This permits soil fauna to make relatively easy adjustments to unfavorable conditions. The number of different species, representing practically every invertebrate phylum found in the soil is enormous. There are 250 species of protozoa alone in English soil. In the soil of beech woods in Austria live at least 110 species of beetles, 229 species of mites, 46 species of snails and slugs.