ECOLOGY- An Introduction

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Ecology is  defined “as a scientific study of the relationship of the living organisms with each other and with their environment.”

The classical texts of the Vedic period such as the Vedas, the Samhitas, the Brahmanas and the Aranyakas-Upanishads contain many references to ecological concepts .The Indian treatise on medicine, the Caraka- Samhita and the surgical text Susruta-Samhita. contain classification of animals on the basis of habit and habitat, land in terms of nature of soil, climate and vegetation; and description of plants typical to various localities.

Caraka- Samhita contains information where air, land, water and seasons were indispensable  for life and that polluted air and water were injurious for health.

The environment is defined as ‘the sum total of living, non-living components;  influences and events, surrounding an organism.

Components of Environment

  1. Abiotic – Energy, Radiation, TEMP, Water, etc.
  2. Biotic- plants, animals, man, DECOMPOSER ETC.

Diesel engine exhaust fumes can cause cancer, humans” and it belong to the same potentially deadly category as asbestos, arsenic and ‘mustard gases.

Six main levels of organisation of ecology are:

  1. Individual- Organism is an individual living being that has the ability to act or function independently.
  2. Population-Population is a group of organisms usually of the same species,

occupying a defined area during a specific time,

  1. Community- Communities in most instances are named after the dominant plant form

(species). A community is not fixed or rigid; communities may be large or small.

Types of Community-

On the basis of size and degree of relative independence communities may be divided into two types-

(a)  Major Community

These are large-sized, well organized and relatively independent. They depend

only on the sun’s energy from outside and are independent of the inputs and

outputs from adjacent communities.

E.g: tropical ever green forest in the North-East

 

(b) Minor Communities

These are dependent on neighbouring communities and are often called societies.

They are secondary aggregations within a major community and are not therefore completely independent units as far as energy and nutrient dynamics are concerned.

e.g: A mat of lichen on a cow dung pad.

The environmental factors determine the characteristic of the community as well as the pattern of organisation of the members in the community

The characteristic pattern of the community is  termed as structure which is reflected in the roles played by various population, their range, the  type of area they inhabit, the diversity of species in the community and the spectrum of interactions between them

Eco-System-An ecosystem is defined as a structural and functional unit of biosphere consisting of community of living beings and the physical environment, both interacting and exchanging materials between them. It includes plants, trees, animals, fish, birds, micro-organisms, water, soil, and  people.

When an ecosystem is healthy (i.e. sustainable) it means that all the elements live in balance and are  capable of reproducing themselves

Continental Drift Theory – Tectonics

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The continental drift theory is the theory that once all the continents were joined in a super-continent, which scientists call Pangaea. Over a vast period of time, the continents drifted apart to their current locations. Alfred Wegener first supported continental drift.

Wegener’s explanation of continental drift in 1912 was that drifting occurred because of the earth’s rotation. Fossil records from separate continents, particularly on the outskirts of continents show the same species.

Orogenic or the mountain-forming movements

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Orogenic or the mountain-forming movements act tangentially to the earth surface, as in plate tectonics.

Tensions produces fissures (since this type of force acts away from a point in two directions) and compression produces folds (because this type of force acts towards a point from two or more directions). In the landforms so produced, the structurally identifiable units are difficult to recognise.

In general, diastrophic forces which have uplifted lands have predominated over forces which have lowered them.

Orogenic- mountain-forming movements

Sudden Movements

These movements cause considerable deformation over a short span of time, and may be of two types.

Earthquake

It occurs when the surplus accumulated stress in rocks in the earth’s interior is relieved through the weak zones over the earth’s surface in form of kinetic energy of wave motion causing vibrations (at times devastating) on the earth’s surface. Such movements may result in uplift in coastal areas.

An earthquake in Chile (1822) caused a one-metre uplift in coastal areas.

An earthquake in New Zealand (1885) caused an uplift of upto 3 metres in some areas while some areas in Japan (1891) subsided by 6 metres after an earthquake.

Earthquakes may cause change in contours, change in river courses, ‘tsunamis’ (seismic waves created in sea by an earthquake, as they are called in Japan) which may cause shoreline changes, spectacular glacial surges (as in Alaska), landslides, soil creeps, mass wasting etc.

Volcanoes

Volcanism includes the movement of molten rock (magma) onto or toward the earth’s surface and also formation of many intrusive and extrusive volcanic forms.

A volcano is formed when the molten magma in the earth’s interior escapes through the crust by vents and fissures in the crust, accompanied by steam, gases (hydrogen sulphide, sulphur dioxide, hydrogen chloride, carbon dioxide) and pyroclastic material. Depending on chemical composition and viscosity of the lava, a volcano may take various forms.

Pyroclastic  adjective of or denoting rock fragments or ash erupted by a volcano, especially as a hot, dense, destructive flow.

Earth Movements – Endogenetic Movements

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The interaction of matter and temperature generates these forces or movements inside the earth’s crust. The earth movements are mainly of two types: diastrophism and the sudden movements.

The energy emanating from within the earth is the main force behind endogenic geomorphic processes.

This energy is mostly generated by radioactivity, rotational and tidal friction and primordial heat from the origin of the earth. This energy due to geothermal gradients and heat flow from within induces diastrophism and volcanism in the lithosphere.

Diastrophism

Diastrophism is the general term applied to slow bending, folding, warping and fracturing.

Wrap == make or become bent or twisted out of shape, typically from the action of heat or damp; make abnormal; distort.

All processes that move, elevate or build up portions of the earth’s crust come under diastrophism. They include:

orogenic processes involving mountain building through severe folding and affecting long and narrow belts of the earth’s crust;

epeirogenic processes involving uplift or warping of large parts of the earth’s crust;

earthquakes involving local relatively minor movements;

plate tectonics involving horizontal movements of crustal plates.

In the process of orogeny, the crust is severely deformed into folds. Due to epeirogeny, there may be simple deformation. Orogeny is a mountain building process whereas epeirogeny is continental building process.

Through the processes of orogeny, epeirogeny, earthquakes and plate tectonics, there can be faulting and fracturing of the crust. All these processes cause pressure, volume and temperature (PVT) changes which in turn induce metamorphism of rocks.

Epeirogenic or continent forming movements

In geology, Epeirogenic movement refers to upheavals or depressions of land exhibiting long wavelengths [undulations] and little folding.

The broad central parts of continents are called cratons, and are subject to epeirogeny.

The movement is caused by a set of forces acting along an Earth radius, such as those contributing to Isostacy and Faulting in the lithosphere

Epeirogenic or continent forming movements act along the radius of the earth; therefore, they are also called radial movements. Their direction may be towards (subsidence) or away (uplift) from the center. The results of such movements may be clearly defined in the relief.

Uplift

Raised beaches, elevated wave-cut terraces, sea caves and fossiliferous beds above sea level are evidences of uplift.

Raised beaches, some of them elevated as much as 15 m to 30 m above the present sea level, occur at several places along the Kathiawar, Nellore, and Thirunelveli coasts.

Several places which were on the sea some centuries ago are now a few miles inland. For example, Coringa near the mouth of the Godavari, Kaveripattinam in the Kaveri delta and Korkai on the coast of Thirunelveli, were all flourishing sea ports about 1,000 to 2,000 years ago.

Epeirogenic movement – uplift

Subsidence

Submerged forests and valleys as well as buildings are evidences of subsidence.

In 1819, a part of the Rann of Kachchh was submerged as a result of an earthquake.

Presence of peat and lignite beds below the sea level in Thirunelveli and the Sunderbans is an example of subsidence.

The Andamans and Nicobars have been isolated from the Arakan coast by submergence of the intervening land.

Epeirogenic movement – subsidence – arakan yomaEpeirogenic movement – subsidence – arakan yoma

On the east side of Bombay island, trees have been found embedded in mud about 4 m below low water mark. A similar submerged forest has also been noticed on the Thirunelveli coast in Tamil Nadu.

A large part of the Gulf of Mannar and Palk Strait is very shallow and has been submerged in geologically recent times. A part of the former town of Mahabalipuram near Chennai (Madras) is submerged in the sea.

Earth’s Layers – Earth’s Composition

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The Crust of Earth

It is the outermost and the thinnest layer of the earth’s surface, about 8 to 40 km thick. The crust varies greatly in thickness and composition – as small as 5 km thick in some places beneath the oceans, while under some mountain ranges it extends up to 70 km in depth.

The crust is made up of two layers­ an upper lighter layer called the Sial (Silicate + Aluminium) and a lower density layer called Sima (Silicate + Magnesium).The average density of this layer is 3 gm/cc.

The Mantle of Earth

This layer extends up to a depth of 2900 km.

Mantle is made up of 2 parts: Upper Mantle or Asthenosphere (up to about 500 km) and Lower Mantle. Asthenosphere is in a semi­molten plastic state, and it is thought that this enables the lithosphere to move about it. Within the asthenosphere, the velocity of seismic waves is considerably reduced (Called ‘Low Velocity

The line of separation between the mantle and the crust is known as Mohoviricic Discontinuity.

 

The Core of Earth

Beyond a depth of 2900 km lies the core of the earth.The outer core is 2100 km thick and is in molten form due to excessive heat out there. Inner core is 1370 km thick and is in plasticform due to the combined factors of excessive heat and pressure. It is made up of iron and nickel (Nife) and is responsible for earth’s magnetism. This layer has the maximum specific gravity.The temperatures in the earth’s core lie between 2200°c and 2750°c. The line of separation between the mantle and the core is called Gutenberg­Wiechert Discontinuity.

Earth’s Interior – Earthquake Waves – Shadow Zone

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Most of the knowledge we have about Earth’s deep interior comes from the fact that seismic waves penetrate the Earth and are recorded on the other side.  Earthquake ray paths and arrival times are more complex than illustrated in the animations, because velocity in the Earth does not simply increase with depth. Velocities generally increase downward, according to Snell’s Law, bending rays away from the vertical between layers on their downward journey; velocity generally decreases upward in layers, so that rays bend toward the vertical as they travel out of the Earth . Snell’s Law also dictates that rays bend abruptly inward at the mantle/outer-core boundary (sharp velocity decrease in the liquid) and outward at the outer core/inner core boundary (sharp velocity increase).

Major Points to remember about P S and Love waves

  • P wave or primary wave. This is the fastest kind of seismic wave, and, consequently, the first to ‘arrive’ at a seismic station.
  • The P wave can move through solid rock and fluids, like water or the liquid layers of the earth.
  • P waves are also known as compressional waves.
  • S wave or secondary wave, which is the second wave you feel in an earthquake. An S wave is slower than a P wave and can only move through solid rock, not through any liquid medium.
  • Travelling only through the crust, surface wavesare of a lower frequency than body waves, and are easily distinguished on a seismogram as a result.

Cultural Achievements of the Pallavas

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Civilization and Culture of the Pallavas

The Pallava rule formed a golden epoch in the cultural history of south India. The period under the Pallavas was marked by considerable literary activities and cultural revival. The Pallavas warmly patronized Sanskrit language and most of the literary records of the time were composed in that language. Due to the cultural renaissance and a great revival of the Sanskrit language a galaxy of scholars flourished during the Pallava era, which accentuated the literary and cultural development in Southern India. Tradition referred that Simhavishnu, the Pallava king invited the great poet Bharvi to adorn his court. Dandin, the master of Sanskrit prose probably lived in the court of Narasimhavarmana II. Under the royal patronage, Kanchi became the seat of Sanskrit language and literature. The core of learning and education, Kanchi became the point of attraction for the literary scholars. Dinanaga, Kalidasa, Bharvi, Varahamihir etc were the distinguished person with enormous talent in the Pallava country. Not only the Sanskrit literature, the Tamil literature also received a huge impetus during the Pallava period. “Maatavailasa Prahasana”, written by Mahendravarmana became very popular. The famous Tamil classic “Tamil Kural was composed during the period under the royal patronage. Madurai became a great center of the Tamil literature and culture. The Tamil grammar “Talakappiam” and Tamil versical compilation “Ettalogai” etc were composed during the period. These were of immense literary importance.

From the 6th century AD, due to the Sanskrit revival, long poetical composition replaced the earlier style of the short poetry. Poetry was written according to the taste of the sophisticated and aristocratic people of the society. The “Silappadigaram” is one of such work suited to the taste of the sophisticated, educated people of the Pallava era. One of the most important literary works of the time was “Ramayanam” by Kaban. This is known as the Tamil form and version of Ramayana, where the character of Ravana was painted with all the noble virtues in comparison to Rama. It is consistent with the Tamil tradition and Tamil ego against the Northern Ramayana by Valmiki. The Buddhist literary work “Manimekhala” and the Jaina poetical work “Shibaga sindamani” etc. also flourished during the period.

The devotional songs composed by Vaishnava Alavaras and the Saiva Nayanaras also shared a significant position in the cultural renaissance of the Pallava period. Appar, Sambandhar, Manikkabsagar, Sundar were some of the devotional Narayana poets who composed Tamil Stotras or hymns. Siva was the object of worship and love. Since the Pallava kings were great musicians themselves they were the great patrons of music. Several celebrated musical treatise were also composed under their patronage. During the time painting also received a great patronage from the Pallava kings. Specimen of the Pallava painting has been found in the Pudukottai State.

Civilization of the Pallava period was greatly influenced by the religious reform movement that swept over India during the eighth century. The wave of the reform movement was originated in the Pallava kingdom first. The Pallavas completed the Aryanisation of Southern India. The Jains who had entered south India earlier had set up educational centers at Madurai and Kanchi. They also made a massive use of Sanskrit, Prakrit and Tamil as the medium of their preaching. But in the competition with the growing popularity of the Brahmanical Hinduism, Jainism lost its prominence in the long run.

Mahendravarmana lost interest in Jainism and became a staunch follower and patron of Saivism. Consequently Jainism began to fade out and continued in diminishing glory in centers like Pudukottai and in the hilly and forest regions.

Buddhism, which had earlier penetrated in the south, fought against invading Brahmanism in the monasteries and public debates. The Buddhist scholars debated finer points of theology with Brahmanical scholars and mostly lost the ground.

The civilization of the Pallava period was marked by the tremendous ascendancy of the Hinduism, which has been branded by the modern historians as the victory of the northern Aryanism. It is said that the influx of the mlechcha Sakas, Huns and the Kushanas in Northern India had polluted the significance of the Vedic rites and religion. In order to protect the purity of Vedic religion many Brahmins migrated to Southern India and preached the Vedic Religion. Henceforth the civilization of Deccan or southern India was mostly influenced by the Brahmanical Hinduism. Pallavas became the patrons of the orthodox Vedic preachers. The performance of the horse sacrifices by the Pallava rulers testified the ascendancy of the Vedic civilization. The success of Hinduism was mostly caused by the royal patronage to this religion. Sanskrit was the vehicle of the Brahmanical thought. Hence both the Brahmanical religion and Sanskrit literature made a great progress during the Pallava period. Several centers for the Brahmanical study sprang up. These study centers were closely connected with the temple premises and were known as Ghetikas. The study of the Brahmanical scriptures and literatures was the order of the day. The Pallava kings in order to promote the Brahmanical civilization made land grants or agraharas to the maintenance of the educational institutions. In the 8th century AD, another significant Hindu institution called Mathas or monasteries were in vogue. They were a combination of temple, rest houses, educational centers, debating and discoursing centers and the feeding Houses. The university of Kanchi became the spearhead of Aryan-Brahmanical influences of the South. Kanchi was regarded as one of the sacred cities of the Hindus. The Pallava king though mainly were the worshippers of Vishnu and Siva, they were tolerant towards other religious creeds. Although the religions like Buddhism and Jainism lost its former significance during the Pallava era, yet the civilization of the Pallava period was marked by the multiethnicity promoted by the Pallava kings.