unit 4

UNIT-4

 Environment: Introduction, Multidisciplinary nature of environmental studies- Definition, scope and importance

 Environment

• The word environment is derived from the French word ‘environner’, which means surrounding. Thus, Environment can be defined as the combined interaction of physical, chemical and biological conditions affecting an individual or community in the complex of social and cultural conditions.

Environmental Science As a Multi Disciplinary Field

1 Environmental science and biology

• Biology mainly deals with life and environment factors have affect on living organisms. Interaction between living things and different components of environment will affect the efficiency and combined effect can be known as environmental biochemistry.
• Biological processes in nature profoundly influenced by chemical species existing and these processes will determine the nature of species, their degradation, and synthesis, both in the aquatic and soil environments. Study of such phenomena are the basis of biochemistry of environment 

2 Environmental science v/s chemistry

• Chemistry deals with chemical processes occurring in nature. When these processes are studied in the shape of reaction which affects the existence of different species, with special reference to air, soil and water environment, this relationship is termed as environmental chemistry.
• One of environmental chemistry’s major challenges is the determination of the nature and quantity of specific pollutants in the environments

3 Relationship between environment and economics

• Economic environment refers to all factors or forces, which contribute to economic impact on the man, his activities and his region.
• Resources such as agriculture, dairying, fisheries poultry, horticulture, floriculture and machinery help to improve economic condition. Economic conditions, internal and external factors such as export and import balances create favourable economic environment for fast development of the country.

4 Social system and environment

• Social environment of the society indicate the mental makeup of man’s activities and helps the individual to decide his occupation and use of resources for his development. Infrastructure such as roads, buildings, settlements, communication setup plantation of horticulture and cropped fields are major component which helps to create social environment.
• Using the combination of tools of modern technology indigenous technical knowledge (ITK) can help to fasten the change of physical environment into cultural environment.

 Need for public awareness

Need for Awareness :

1   Environmental science knowledge should be used to educate the masses about the problems being faced by present generation as well as the problems to be faced by future generation. 

2 Multimedia can play leading role for dissemination of information by using different tools like advertisements, group discussion, feature films, video conferencing, and website and internet services.

 3 Printing media can initiate the campaigns regarding impact of degraded environment on living organisms by publishing articles through newspapers, magazines, newsletters.

4 Awareness campaign can be launched through displaying several holdings, posters at   prominent places and organising exhibitions, face to face interaction, online e-mail service, SMS service throughout the country.

 Ecosystem: Concept,  Energy  flow,  Structure  and  function  of  an ecosystem

FIRST GO THROUGH THE THREE  VIDEO LECTURE 

https://www.youtube.com/watch?v=qtTLiQoYTyQ

https://www.youtube.com/watch?v=nFpQCBw6xQM

https://www.youtube.com/watch?v=NkHVUa_fACI

 Ecosystem:

In nature several communities of organisms live together and interact with each other as well as with their physical environment as an ecological unit. We call it an ecosystem

An ecosystem is a functional unit of nature encompassing complex interaction between its biotic (living) and abiotic (non-living) components. For example- a pond is a good example of ecosystem.

Components of an ecosystem

Components of ecosystem: They are broadly grouped into:

(a) Abiotic and

(b) Biotic components

(a) Abiotic components (Nonliving): The abiotic component can be grouped into following three categories:

(i) Physical  factors: Sun light, temperature, rainfall, humidity and pressure. They sustain and limit the growth of organisms in an ecosystem.

(ii) Inorganic substances: Carbon dioxide, nitrogen, oxygen, phosphorus, sulphur, water, rock, soil and other minerals.

(iii) Organic compounds: Carbohydrates, proteins, lipids and humic substances. They are the building blocks of  living systems and therefore, make a link between the biotic and abiotic components.

(b) Biotic components (Living):

(i) Producers: The green plants manufacture food for the entire ecosystem through the process of photosynthesis. Green plants are called autotrophs, as they absorb water and nutrients from the soil, carbon dioxide from the air, and capture solar energy for this process

(ii) Consumers: They are called heterotrophs and they consume food synthesized by the autotrophs. Based on food preferences they can be grouped into three broad categories. Herbivores (e.g. cow, deer and rabbit etc.) feed directly on plants, carnivores are animals which eat other animals (eg. lion, cat, dog etc.) and omnivores organisms feeding upon both plants and animals e.g. human, pigs and sparrow.

(iii) Decomposers: Also called saprotrophs. These are mostly bacteria and fungi that feed on dead decomposed and the dead organic matter of plants and animals by secreting enzymes outside their body on the decaying matter. They play a very important role in recycling of nutrients. They are also called detrivores or detritus feeders

Functions of ecosystem:

Ecosystems are complex dynamic system. They perform certain functions. These are:

(i) Energy flow through food chain

(ii) Nutrient cycling (biogeochemical cycles)

(iii) Ecological succession or ecosystem development

(iv) Homeostasis (or cybernetic) or feedback control mechanisms
Ponds, lakes, meadows, marshlands, grasslands, deserts and forests are examples of natural ecosystem. Many of you have seen an aquarium; a garden or a lawn etc. in your neighbourhood. These are man made ecosystem.

Types of ecosystem:

Ecosystems are classified as follows:

(i) Natural ecosystems

(ii) Man made ecosystems

(i) Natural ecosystems

(a) Totally dependent on solar radiation e.g. forests, grasslands, oceans, lakes, rivers and deserts. They provide food, fuel, fodder and medicines.

(b) Ecosystems dependent on solar radiation and energy subsidies (alternative sources) such as wind, rain and tides. e.g tropical rain forests, tidal estuaries and coral reefs.

(ii) Man made ecosystems

(a) Dependent on solar energy-e.g. Agricultural fields and aquaculture ponds.
(b) Dependent on fossil fuel e.g. urban and industrial ecosystem

ECOSYSTEM FUNCTION–ENERGY FLOW THROUGH ECOSYSTEM


https://www.youtube.com/watch?v=nGbEf87it9A

https://www.youtube.com/watch?v=ctt5wyABFYw

Food chains and energy flow are the functional properties of ecosystems which make them dynamic. The biotic and abiotic components of an ecosystem are linked through them.

 Food Chain

Transfer of food energy from green plants (producers) through a series of organisms with repeated eating and being eaten is called a food chain. e.g. Grasses → Grasshopper → Frog → Snake → Hawk/Eagle
Each step in the food chain is called trophic level. In the above example grasses are 1st, and eagle represents the 5th trophic level.

During this process of transfer of energy some energy is lost into the system as heat energy and is not available to the next trophic level. Therefore, the number of steps are limited in a chain to 4 or 5. Following trophic levels can be identified in a food chain.

(1) Autotrophs: They are the producers of food for all other organisms of the ecosystem. They are largely green plants and convert inorganic material in the presence of solar energy by the process of photosynthesis into the chemical energy (food). The total rate at which the radiant energy is stored by the process of photosynthesis in the green plants is called Gross Primary Production (GPP). This is also known as total photosynthesis or total assimilation. From the gross primary productivity a part is utilized by the plants for its own metabolism. The remaining amount is stored by the plant as Net Primary Production (NPP) which is available to consumers

(2) Herbivores: The animals which eat the plants directly are called primary consumers or herbivores e.g. insects, birds, rodents and ruminants.

(3) Carnivores: They are secondary consumers if they feed on herbivores and tertiary consumers if they use carnivores as their food. e.g. frog, dog, cat and tiger.

(4) Omnivores: Animals that eat both plant and animals e.g. pig, bear and man

(5) Decomposers: They take care of the dead remains of organisms at each trophic level and help in recycling of the nutrients e.g. bacteria and fungi

There are two types of food chains:

(i) Grazing food chains: which starts from the green plants that make food for herbivores and herbivores in turn for the carnivores.

(ii) Detritus food chains: start from the dead organic matter to the detrivore organisms which in turn make food for protozoan to carnivores etc.

In an ecosystem the two chains are interconnected and make y-shaped food chain. These two types of food chains are:(i) Producers → Herbivores → Carnivores (ii) Producers → Detritus Feeders → Carnivores

 Food web

Food web is an important conceptual tool for illustrating the feeding relationships among species within a community, revealing species interactions and community structure, and understanding the dynamics of energy transfer in an ecosystem.Trophic levels in an ecosystem are not linear rather they are interconnected and make a food web. Thus food web is a network interconnected food chains existing in an ecosystem. One animal may be a member of several different food chains. Food webs are more realistic models of energy flow through an ecosystem

Ecological pyramid:

Ecological pyramids are the graphic representations of trophic levels in an ecosystem. They are pyramidal in shape and they are of three types:

a)Pyramid of number: This represents the number of organisms at each trophic level. For example in a grassland the number of grasses is more than the number of herbivores that feed on them and the number of herbivores is more than the number of carnivores. In some instances the pyramid of number may be inverted, i.e herbivores are more than primary producers as you may observe that many caterpillars and insects feed on a single tree

b) Pyramid of biomass: This represents the total standing crop biomass at each trophic level. Standing crop biomass is the amount of the living matter at any given time. It is expressed as gm/unit area or kilo cal/unit area. In most of the terrestrial ecosystems the pyramid of biomass is upright. However, in case of aquatic ecosystems the pyramid of biomass may be inverted e.g. in a pond phytoplankton are the main producers, they have very short life cycles and a rapid turn over rate (i.e. they are rapidly replaced by new plants). Therefore, their total biomass at any given time is less than the biomass of herbivores supported by them

c) Pyramid of energy: This pyramid represents the total amount of energy at each trophic level. Energy is expressed in terms of rate such as kcal/unit area /unit time or cal/unit area/unit time.eg. in a lake autotroph energy is 20810 kcal/m/year . Energy pyramids are never inverted.

Forest ecosystem:

A Forest Ecosystem  is a community of organisms that lives within a forest. A forest is usually defined as a large group of trees.



 The chief components of a forest ecosystem are as follows—

1. Abiotic substances:

In addition to minerals present in the soil, the forest floor is rich in dead and decaying organic matter. 

2. Primary producers:

The dominant producers of the forest ecosystem are the higher forms of the plant kingdom, most specifically seed bearing plants. In forest ecosystem, the producers form three major functions. First, they provide the initial source of food. Second, large plant structures provide habitats for other organisms. Third, they are prime agents in soil formation and in modifying the abiotic environment.

3. Primary consumers:

These are the herbivores that include the foliage arthropods such as ants, flies, beetles, leaf-hoppers, bugs and spiders, etc. and the larger animals grazing on shoots and fruits such as elephants, nilgai, deer, moles, squirrels, shrews, flying foxes, fruit bats and mongooses, etc.

4. Secondary consumers:

These are the carnivores like snakes, birds, lizards and foxes feeding on herbivores. The top carnivores like lion, tiger, etc, prey upon both herbivores and carnivores of the secondary consumer level.

5. Decomposers:
The decomposers of the forest ecosystem, as in other ecosystem, are the bacteria and fungi. These organisms obtain energy to carry on the life functions by breaking down the organic compounds of dead organic matter and organic wastes. In doing so, they prevent the accumulation of organic matter and also release the essential minerals for reuse. Decomposers are mostly found in soil and bacteria are represented by the numerous heterotrophic.

Types of forest ecosystem.

1. Rainforests: Some of the most biodiverse ecosystems on the planet, with the Amazon being a prime example. The north-eastern part of India is particularly rich in rainforests. Further, the tropical rainforests in India are found in Assam, Andaman and Nicobar islands, and Western Ghats, etc.

2. Mangroves: Mangroves are a unique mix of trees and tidal swamps. These fascinating forest ecosystems change greatly throughout the day. During part of the day they are dry and during much of the rest of the day they are waterlogged and home to crocodiles and other swamp creatures. These may be some of the most dynamic ecosystems in the world, for this very reason!

3. Inland forests: Here, you will find plenty of mainland animals and birds (such as foxes and owls). Inland forests can be vast and ancient, or they can be smaller, like copses.

4. The Taiga: The taiga is the name for the sparse forest right towards the polar regions of the world, where conditions can be very cold and quite harsh. In fact, many of the forest ecosystems in the Taiga are arctic or polar ecosystems

5. Lakeside forests: Waterbirds and other water wildlife can be found in these forest ecosystems. These types of forest ecosystems tend to be very humid and the types of organisms that live in them reflect this.

6. Mountain forests: The forests that grow on mountains (such as mountain pines) help to create unique ecosystems. For example, the Himalayan mountain forests in India. The peaks of mountains tend to be cold and rocky and the organisms that live in forest ecosystems at the top of mountains tend to be very well adapted for life in harsh conditions.

Grassland  ecosystem:

Grasslands occupy about 19% of the earth’s surface. The major grassland ecosystems of the world are the great plains of Canada and United States, S. Argentina to Brazil and S. Asia to Central Asia

The various components of a grassland ecosystem are as follows—

1. Abiotic substances:

These include the nutrients present in the soil and the aerial environment. The elements required by plants are hydrogen, oxygen, nitrogen, phosphorous and sulphur. These are supplied by the soil and air in the form of CO₂, water, nitrates, phosphates and sulphates. In addition to these some trace elements are also present in the soil.

2. Primary producers:

These are mainly grasses of the family, Graminae, a large variety of herbs, some shrubs and scattered trees.

3. Consumers:

Herbivores such as grazing mammals (e.g., cows, sheep, deer, rabbit, buf­faloes, etc), insects (e.g., Dysdercus, Coccinella, Leptocorisa, etc), some termites and millipedes are the primary consumers.

The animals like fox, jackals, snakes, frogs, lizard, birds etc., are the carnivores feeding on the herbivores. These are the secondary consumers of the grassland ecosystem. Hawks occupy the tertiary trophic level as these feed on the secondary consumers.

4. Decomposers:

These include bacteria of death and decay, moulds and fungi (e.g., Mitcor, Penicillium, Aspergillus, Rhizopus, etc). These bring the minerals back to the soil to be available to the producers again

The Desert Ecosystem:

The deserts occupy about 17% of the land and occur in the regions with an average rainfall of less than 23 cm. Due to extreme of temperature, the species composition of desert ecosystem is less varied and typical. The various components of a desert ecosystem are—

1. Producers: The shrubs, bushes, grasses and some trees are the main producers in deserts. The shrubs have extensive and much branched root system with the stems and leaves variously modified. Some succulent cacti are also found in deserts. These store water in their stem to be used during the time of water scarcity. Some lower plants such as lichens, xerophytic mosses and blue green algae are also found there.

2. Consumers:

Only a few animals are found in deserts. The most common animals are those reptiles and insects which are able to live under xeric conditions. Mammals are represented by a few species of nocturnal rodents. Some birds are present. The camel, called the ship of desert, feeds on tender shoots of the plants and conserves large quantities of water in its stomach. The larger animals including carnivores are scarce. The desert animals have various morphological and physiological adaptations which enable them to live in such extreme environment.

3. Decomposers:Due to poor vegetation and less amount of dead organic matter decom­posers are few. They are thermophilic fungi and bacteria


 Aquatic ecosystems

An aquatic ecosystem includes a group of interacting organisms which are dependent on one another and their water environment for nutrients and shelter. Examples of aquatic ecosystem include oceans, lakes and rivers.

An aquatic ecosystem includes freshwater habitats like lakes, ponds, rivers, oceans and streams, wetlands, swamp, etc. and marine habitats include oceans, intertidal zone, reefs, seabed and so on. The aquatic ecosystem is the habitat for water-dependent living species including animals, plants, and microbes.

Different types of aquatic ecosystems are as follows:

Freshwater Aquatic Ecosystem

They cover only a small portion of earth nearly 0.8 per cent. Freshwater involves lakes, ponds, rivers and streams, wetlands, swamp, bog and temporary pools. Freshwater habitats are classified into lotic and lentic habitats. Water bodies such as lakes, ponds, pools, bogs, and other reservoirs are standing water and known as lentic habitats. Whereas lotic habitats represent flowing water bodies such as rivers, streams.

Marine Aquatic Ecosystem:

Marine ecosystem covers the largest surface area of the earth. Two third of earth is covered by water and they constitute of oceans, seas, intertidal zone, reefs, seabed, estuaries, hydrothermal vents and rock pools. Each life form is unique and native to its habitat. This is because they have adaptations according to their habitat. In the case of aquatic animals, they can’t survive outside of water. Exceptional cases are still there which shows another example of adaptations (e.g. mudskippers). The marine ecosystem is more concentrated with salts which make it difficult for freshwater organisms to live in. Also, marine animals cannot survive in freshwater. Their body is adapted to live in saltwater; if they are placed in less salty water, their body will swell (osmosis)

 Environmental Pollution: Definition, Cause, effects and control measures :

FOR DIFFERENT TYPES OF PULLUTION USE BELOW MENTIONED LINK

http://ecoursesonline.iasri.res.in/mod/page/view.php?id=89612