Definition, principles and scope of Environmental Science

The word 'Environment' is derived from the French word 'Environner' which means to encircle, around or surround. The biologist Jacob Van Uerkal (1864-1944) introduced the term environment in ecology. As given by Environment Protection Act 1986, Environment is the sum total of land, water, air, interrelationships among themselves and also with the human beings and other living organisms. Environmental science is an interdisciplinary field that integrates physical, biological, and social sciences to study the environment and its complex interactions with human societies. It aims to understand the natural world, identify environmental issues, and develop sustainable solutions to address environmental challenges. 

A) Definitions of Environment : 

1. Douglas and Holland(1947):  Environment is a word which describing the aggregate, all of the extrinsic (external) forces influences and conditions which affect the life, nature, behaviour and the growth, development and maturation of living organisms.
2. Woodworth and Marques(1948): Environment covers all the outside factors that have acted on the individual since he began life.
3. Boring : According to Boring "A person's environment consists of the sum total of the stimulation which he receives from his conception until his death".

B) Principles of Environmental Science:

1. Interdisciplinary Approach: Environmental science draws on knowledge from various scientific disciplines, including biology, chemistry, physics, geology, ecology, and sociology, to study the environment comprehensively.
2. Sustainability: The principle of sustainability emphasises meeting the needs of the present without compromising the ability of future generations to meet their own needs. Environmental science seeks to promote sustainable practices that conserve natural resources and protect ecosystems. 
3. Conservation: Environmental science advocates for the conservation of biodiversity, natural habitats, and ecosystem services to maintain ecological balance and promote long-term environmental health.
4. Pollution Prevention: Environmental science focuses on identifying sources of pollution, minimizing waste generation, and implementing strategies to prevent pollution and protect air, water, and soil quality.
5. Environmental Justice: Environmental science addresses environmental inequalities and advocates for equitable access to clean air, water, and land for all communities, regardless of socioeconomic status or geographic location.

C) Scope of Environmental Science:

1. Environmental Issues: Environmental science investigates a wide range of environmental issues, including climate change, deforestation, pollution, habitat loss, biodiversity loss, resource depletion, and waste management.

2. Sustainable Development: Environmental science plays a crucial role in promoting sustainable development practices that balance economic growth with environmental protection and social equity.

3. Conservation Biology: Environmental science includes the study of conservation biology, which focuses on preserving biodiversity, protecting endangered species, and restoring degraded ecosystems.

4. Environmental Policy: Environmental science informs environmental policy-making by providing scientific data and analysis to support evidence-based decision-making on environmental issues at local, national, and global levels.

5. Environmental Education: Environmental science contributes to environmental education initiatives that raise awareness about environmental issues, promote eco-friendly behaviour, and empower individuals to take action to protect the environment.

Components of Environment:

Atmosphere: The protective blanket of gases surrounding the earth: 

1. It sustains life on the earth, it saves it from the hostile environment of outer space, 
2. it absorbs most of the cosmic rays from outer space and a major portion of the electromagnetic radiation from the sun and
3. it transmits only here ultraviolet, visible, near infrared radiation (300 to 2500 nm) and radio waves. (0.14 to 40m) while filtering out tissue-damaging ultraviolet waves below about 300 nm.

The atmosphere is composed of nitrogen and oxygen. Besides, argon, carbon dioxide, and trace gases.

Hydrosphere: The Hydrosphere comprises all types of water resources oceans, seas, lakes, rivers, streams, reservoir, polar ice caps, glaciers, and groundwater. 

1. Nature 97% of the earth's water supply is in the oceans,
2. About 2% of the water resources is locked in the polar icecaps and glaciers.
3. Only about 1% is available as fresh surface water-rivers, lakes streams, and groundwater fit to be used for human consumption and other uses.

Lithosphere: The word lithosphere originated from a Greek word mean "rocky" + "sphere” i.e. the solid outmost shield of the rocky planet. The Earth is an oblate spheroid. It is composed of a number of different layers.

1. The Core which is around 7000 kilometres in diameter (3500 kilometres in radius) and is situated at the Earth's centre.
2. The Mantle which environs the core and has a thickness of 2900 kilometres.
3. The Crust floats on top of the mantle and is composed of basalt rich oceanic crust and granitic rich continental crust. 

Biosphere: Indicates the realm of living organisms and their interactions with environment, viz atmosphere, hydrosphere and lithosphere.

In summary, environmental science is a multidisciplinary field that addresses environmental challenges through scientific research, policy development, conservation efforts, and education to promote sustainable practices and safeguard the health of the planet and its inhabitants.

Physico-chemical and Biological factors in the Environment

Physico-chemical and biological factors are essential components of the environment that interact and influence each other to shape ecosystems and determine the health and functioning of natural systems. Understanding these factors is crucial in environmental science to assess environmental quality, monitor changes, and develop effective management strategies. 

Here is an overview of Physico-chemical and biological factors in the environment:

1. Physico-Chemical Factors:

1. Temperature: Temperature influences various biological processes, such as metabolism, growth, reproduction, and species distribution. Extremes in temperature can stress organisms and impact ecosystem dynamics.

2. Light: Light availability affects photosynthesis, plant growth, and the behaviour of organisms. Light intensity, duration, and quality play a significant role in shaping ecosystems.

3. Water: Water availability and quality are critical for all living organisms. Factors such as pH, salinity, dissolved oxygen, and pollutants in water can affect aquatic ecosystems and the health of aquatic organisms.

4. Soil: Soil properties, including texture, structure, pH, nutrient content, and organic matter, influence plant growth, soil fertility, and ecosystem productivity.

5. Air Quality: Air pollutants, such as particulate matter, nitrogen oxides, sulphur dioxide, and volatile organic compounds, can impact human health, vegetation, and ecosystems.

6. Chemical Pollution: Chemical contaminants from industrial activities, agriculture, and urban runoff can have detrimental effects on ecosystems and human health.

2. Biological Factors:

1. Biodiversity: Biodiversity refers to the variety of living organisms in an ecosystem. High biodiversity supports ecosystem resilience, productivity, and stability.

2. Species Interactions: Interactions between species, such as competition, predation, mutualism, and parasitism, play a crucial role in shaping ecosystems and maintaining ecological balance.

3. Population Dynamics: Population dynamics involve the study of population size, density, growth rates, distribution, and interactions within a species. Understanding population dynamics is essential for conservation efforts and ecosystem management.

4. Adaptations: Organisms have evolved a variety of adaptations to survive and thrive in different environments. Adaptations can include physical traits, behaviours, and physiological mechanisms that help organisms cope with environmental challenges.

5. Food Chains and Webs: Food chains and food webs illustrate the flow of energy and nutrients through ecosystems. They show how organisms are interconnected and dependent on each other for survival.

By considering the interactions between Physico-chemical and biological factors in the environment, environmental scientists can assess the health of ecosystems, predict responses to environmental changes, and develop strategies to protect and restore natural systems for the benefit of both humans and wildlife.

Structure and composition of atmosphere

What is atmosphere? 

We all know that earth is a unique planet due to the presence of life. The air is one among  the necessary conditions for the existence of life on this planet. The air is a mixture of  several gases and it encompasses the earth from all sides. The air surrounding the earth is  called the atmosphere OR  the gaseous canopy that envelops the lithosphere and the hydrosphere is known as the  atmosphere. Atmosphere is the air surrounding the earth. The atmosphere is a mixture of different gases. It contains life-giving gases like Oxygen for humans and animals and carbon dioxide for plants. 

It envelops the earth all round and is held in place by the gravity of the earth. It helps in stopping the ultraviolet rays harmful to the life and maintains the suitable  temperature necessary for life. Generally, atmosphere extends up to about 1600 km from the earth’s surface.  However, 99 % of the total mass of the atmosphere is confined to the height of 32 km  from the earth’s surface.

Composition of the atmosphere

The atmosphere is made up of different gases, water vapour and dust particles. The composition of the atmosphere is not static and it changes according to the time  and place. The atmosphere is a mixture of different types of gases. 

1. Nitrogen and oxygen are the two main gases in the atmosphere and 99 percentage of  the atmosphere is made up of these two gases. 
2. Other gases like argon, carbon dioxide, neon, helium, hydrogen, etc. form the  remaining part of the atmosphere. 
3. The portion of the gases changes in the higher layers of the atmosphere in such a way  that oxygen will be almost negligible quantity at the heights of 120 km.
4. Similarly, carbon dioxide (and water vapour) is found only up to 90 km from the surface  of the earth.

CARBON DIOXIDE: 

1. Carbon dioxide is meteorologically a very important gas. 
2. It is transparent to the incoming solar radiation (insolation) but opaque to the outgoing  terrestrial radiation. 
3. It absorbs a part of terrestrial radiation and reflects back some part of it towards the  earth’s surface. 
4. Carbon dioxide is largely responsible for the greenhouse effect.
5. When the volume of other gases remains constant in the atmosphere, the volume of  the carbon dioxide has been rising in the past few decades mainly because of the  burning of fossil fuels. This rising volume of carbon dioxide is the main reason for  global warming. 
   

OZONE GAS: 

1. Ozone is another important component of the atmosphere found mainly between 10  and 50 km above the earth’s surface. 
2.  It acts as a filter and absorbs the ultra-violet rays radiating from the sun and prevents  them from reaching the surface of the earth. 
3. The amount of ozone gas in the atmosphere is very little and is limited to the ozone  layer found in the stratosphere.
   

 DUST PARTICLES

1. Dust particles are generally found in the lower layers of the atmosphere.
2. These particles are found in the form of sand, smoke-soot, oceanic salt, ash, pollen,  etc. 
3. Higher concentration of dust particles is found in subtropical and temperate regions  due to dry winds in comparison to equatorial and polar regions.
4.  These dust particles help in the condensation of water vapour. During the  condensation, water vapour gets condensed in the form of droplets around these dust  particles and thus clouds are formed. 

Structure of the atmosphere 

Mesosphere (50-80km)

1. It is the third layer of the atmosphere spreading over the stratosphere. It extends up to a height of 80 km. 
2. In this layer, the temperature starts decreasing with increasing altitude and reaches up  to -100 degree Celsius at the height of 80 km. 
3. Meteors or falling stars occur in this layer. 
4. The upper limit of the mesosphere is known as mesopause. 
   

Thermosphere (80-550km)

1. This layer is located between 80 and 550 km above the mesopause.  It contains electrically charged particles known as ions, and hence, it is known as  the ionosphere. 
2. Radio waves transmitted from the earth are reflected back to the earth by this layer  and due to this, radio broadcasting has become possible.
3. The temperature here starts increasing with heights. 
   

Exosphere (550-1000km)

1. The exosphere is the uppermost layer of the atmosphere. 
2. Gases are very sparse in this sphere due to the lack of gravitational force.
3. Here, air density is extremely low and hydrogen and helium gases  predominate.
   
   

Magnetosphere(above 1000km)

1. The area around the earth that extends beyond the atmosphere.
2. It is made up of positively and negatively charged particles. When this particles collide with each other causing the aurora borealis.

Structure and composition of hydrosphere

The Hydrosphere: 

The hydrosphere, or water sphere, mostly covers the depressions of the lithosphere. Some  amount of water is also found in the rocks and much exists in the form of water vapour in  the atmosphere. The oceans represent about 71 per cent of the globe and therefore contain  the great bulk of the water. The average depth of the oceans is about 3,800 m. 

The total volume of the world oceans is about 1-4 billion cu. km. which comprises more  than 97 per cent of the world’s free water. Of the remaining 3 per cent, about 2 per cent is  locked up in the ice sheets of Arctic and Antarctica and about 1 per cent is being  represented by fresh water of the lands. 

Sea or ocean water is a solution of salt whose constituents have maintained more or less  fixed proportions over a considerable span of geologic time. In addition to their importance  in the chemical environment of marine life, these salts make up a vast store-house of  mineral matter. 

1. The earth’s water moves through an interesting cycle known as hydrological cycle.
2. It is  made up of two parts. In the first of atmospheric part, the horizontal movement of water  vapour predominates.
3. In the terrestrial, the second part, the movement of water in the  liquid and solid phase predominates. 
   

By evaporation, water enters the air as water vapour from the oceans and other water bodies as also from plants and animals by transpiration. As the water vapour moves up the  air it condenses and ultimately returns to the surface as precipitation.

From the land it returns back to the oceans or adds directly to the air through evaporation  and transpiration. This functional interrelation of hydrosphere, atmosphere and lithosphere  makes possible the continued existence of plant and animal life. 

Structure and composition of lithosphere

 Lithosphere

The  lithosphere is the solid, outer  part of theEarth. The lithosphere includes the brittle upper portion of the mantle and the crust, the outermost layers of Earth's structure. It is bounded by the atmosphere above and the asthenosphere (another part of the upper mantle) below. The asthenosphere is partially molten upper mantle material that behaves plastically and can flow. 

There are two types of lithosphere: oceanic lithosphere and continental lithosphere 

1. Oceanic lithosphere is associated with oceanic crust, and is slightly denser than continental lithosphere. The  continental lithosphere is also called the continental crust.
2. Oceanic crust is composed of magma that erupts on the seafloor to create basalt lava flows or cools deeper down to create the intrusive igneous rock gabbro. Sediments, primarily muds and the shells of tiny sea creatures, coat the seafloor. Sediment is thickest near the shore where it comes off the continents in rivers and on wind currents.
3. Continental crust is made up of many different types of igneous, metamorphic, and sedimentary rocks. The average composition is granite, which is much less dense than the mafic igneous rocks of the oceanic crust. Because it is thick and has relatively low density, continental crust rises higher on the mantle than oceanic crust, which sinks into the mantle to form basins. 

Crust

1. The Earth's outermost layer, its crust, is rocky and rigid.
2. There are two kinds of crust: continental crust, and ocean crust. Continental crust is thicker, and predominantly felsic in composition, meaning that it contains minerals that are richer in silica. The composition is important because it makes continental crust less dense than oceanic crust.
3. Ocean crust is thinner, and predominantly mafic in composition. Mafic rocks contain minerals with less silica, but more iron and magnesium. Mafic rocks (and therefore ocean crust) are denser than the felsic rocks of continental crust.
4. The crust floats on the mantle. Continental crust floats higher in the mantle than oceanic crust because of the lower density of continental crust.
5. An important consequence of the difference in density is that if tectonic plates happen to bring ocean crust and continental crust into collision, the plate with oceanic crust will be forced down into the mantle beneath the plate with continental crust.

Mantle

The mantle represents about 68% of the mass of the earth.

1. It is subdivided into upper, transition and lower zones and form 84 percent of the earth volume.
2. The upper mantle extends to about 400kms  and contains silicate material olivine, pyroxene.
3. T r a n s i t i o n  z o n e -  400km to 1000kms (olivine, pyroxene)
4. Lower zone-1000 kms-2900kms (FEMIC)
5. Like in crust oxygen most  dominant element in the mantle and siliconi sthe second most abundant element in the mantle.
6. The density of the layer is higher than the crust and varies from 3.3 - 5.4g/cm3.
7. The portion of the mantle which is just below the lithosphere and asthenosphere, but above the core is called as Mesosphere.

Core (15% of earth volume)

1. The core is primarily composed of iron, with lesser amounts of nickel.
2. Lighter elements such as sulfur, oxygen, or silicon may also be present. The core is extremely hot (~3500° to more than 6000°C). But despite the fact that the boundary between the inner and outer core is approximately as hot as the surface of the sun, only the outer core is liquid.
3. The outer core-2900 km to 5080 km  and in liquid state mainly iron(NIFE).
4. The inner core is solid because the pressure at that depth is so high that it keeps the core from melting(5080-6370 kms and contain pure iron).
5. The core constitutes nearly 15% of earth's volume and 32.5% of earth's mass.
6. The core is the densest layer of the earth with its density ranges between 9.5-14.5g/cm3.
7. Barysphere  is  sometimes used to refer the core of the earth or sometimes the whole interior.
   

Evolution of biosphere

Evolution of  Biosphere

The evolution of the biosphere is a fundamental concept in environmental science that traces the development and changes in life on Earth over billions of years. Understanding the evolution of the biosphere provides insights into the interconnectedness of living organisms with their environment, the adaptation of species to changing conditions, and the shaping of ecosystems through evolutionary processes.

Here are key points related to the evolution of the biosphere in the context of environmental science:

1. Origin of Life: The biosphere began with the origin of life on Earth approximately 3.8 billion years ago. The exact mechanisms by which life originated are still a topic of scientific debate, but it is believed to have emerged from simple organic molecules in a primordial soup under conditions conducive to chemical reactions.

2. Evolutionary Processes: Evolution is the process by which species change over time through genetic variations, natural selection, and adaptation to environmental conditions. Evolutionary processes drive the diversity of life forms in the biosphere and shape the interactions between organisms and their surroundings.

3. Speciation: Speciation is the process by which new species arise from existing ones. It occurs through mechanisms such as geographic isolation, genetic drift, and natural selection. Speciation leads to the formation of biodiversity within ecosystems.

4. Extinction Events: Throughout Earth's history, mass extinction events have occurred, leading to the loss of a significant proportion of species. These events can be caused by natural factors such as volcanic eruptions, asteroid impacts, or climate change, as well as human activities such as habitat destruction and pollution.

5. Adaptation and Survival: Organisms in the biosphere have evolved a wide range of adaptations to survive and thrive in different environments. These adaptations can include physical characteristics, behaviors, and physiological mechanisms that enhance an organism's chances of survival and reproduction.

6. Ecosystem Dynamics: Ecosystems are dynamic and constantly changing systems shaped by interactions between biotic (living) and abiotic (non-living) components. The evolution of species within ecosystems influences their structure, functioning, and resilience to environmental disturbances.

7. Human Impact: The evolution of the biosphere has been significantly influenced by human activities in recent centuries. Human-induced changes to ecosystems, such as deforestation, pollution, overexploitation of resources, and climate change, have altered natural habitats and put pressure on biodiversity.

By studying the evolution of the biosphere, environmental scientists gain insights into the interconnectedness of life on Earth, the processes that drive biodiversity, and the importance of conservation and sustainable management of natural resources to ensure the health and resilience of ecosystems for future generations.