UNIT 2

Ecosystems

1. Explain Concept of an ecosystem?

Concept of an ecosystem

Term ‘Ecosystem’ was tossed in the year 1935 by an English Botanist- A.G. Tansley.

An ecosystem is a geographic area which contains both Biotic as well as Abiotic factors and their interaction with each other.

There are various types of Ecosystems such as:

• Terrestrial
• Aquatic
• Desert
• Grassland
• Forests
• Marine
• Freshwater, etc.

1. Explain Structure and function of an ecosystem?

Ecosystem has 2 major components:

1)     Biotic (Living)

2)     Abiotic (Non- Living)

These 02 components when interacts with each other in a system, then give rise to an ecosystem.

Biotic Components are of 3 further types:

1)     Producers

2)     Consumers

3)     Decomposers

Abiotic Components are of 3 sorts:

1)     Climatic Factors (Rain, Lightning, Humidity, Wind, Temperature, etc.)

2)     Edaphic Factors (Soil based factors such as pH, minerals, etc.)

Classification of Ecosystem and its components

Functions:

Basic function of ecosystem is merely an exchange of energy and nutrients in the food chain which impacts the survival of existence of all life forms. This exchange is responsible for the setting up of equilibrium between biotic and abiotic components.

2.     Describe Producers, consumers and decomposers?

1)     Producers: They prepare their own food and initiate the cycle.

Example: Plants prepare their own food with the help of photosynthesis.

2)     Consumers: These are primary (who feeds on producers) & secondary (who feed on both producers and primary consumers)

Example: Herbivores & Carnivores

3)     Decomposers: Feeds on dead of lifeless residues of producers and consumers.

Example: Bacteria, Fungi, etc.

3.     Explain Energy flow in the ecosystem?

The behavior of energy in ecosystem can be conveniently termed as energy flow because of unidirectional energy transformations. Total energy flow that constitutes the energy environment has already been dealt in detail, and now we take up the study of that portion of the total energy flow that passes through the biotic components of the ecosystem. Entrance of energy, its retention within the ecosystem and dissipation into space, are governed by two laws of thermodynamics. According to the first law, the law of conservation of energy, in a closed system, no energy comes in or escapes out and not created or destroyed but may be altered from one form to another. The second law of thermodynamics, the law of entropy, states that there is always a tendency for increase in entropy or degradation from a concentrated (non-random) to a dispersed (random) form leading to dissipation of heat. All the energy entering the earth’s surface can be accounted for. Some energy is used in photosynthesis; the rest is used in converting the water into vapours or heating the soil and air. Ultimately the energy reflected back to outer space as heat. The light energy fixed by green plants in the process of photosynthesis may be represented by the following equation:

Out of the amount of energy so fixed by green plants, some is released again in respiration. The fixed energy, in the form of food, then passes from plant source through herbivores to carnivores. At each stage of food transfer, potential energy is released, resulting in further loss of a large part of energy. The energy flow, thus follows the second law of thermodynamics.

4.     What is Ecological succession?

Ecological succession is the phenomenon or process by which an ecological community undergoes more or less orderly and predictable changes following disturbance or initial colonization of new habitat. Succession was among the first theories advanced in ecology and the study of succession remains at the core of ecological science. Succession may be initiated either by formation of new, unoccupied habitat (e.g., a lava flow or a severe landslide) or by some form of disturbance (e.g. Fire, severe wind throw, logging) of an existing community.

1. Primary succession

Succession that begins in new habitats, uninfluenced by pre-existing communities is called primary succession. In primary succession pioneer species like lichen, algae and fungus as well as other abiotic factors like wind and water start to "normalize" the habitat. This creating conditions nearer optimum for vascular plant growth; pedogenesis or the formation of soil is the most important process.

These pioneer plants are then dominated and often replaced by plants better adapted to less odd conditions, these plants include vascular plants like grasses and some shrubs that are able to live in thin soils that are often mineral based.

For example, spores of lichen or fungus, being the pioneer species, are spread onto a land of rocks. Then, the rocks are broken down into smaller pieces and organic matter gradually accumulates, favouring the growth of larger plants like grasses, ferns and herbs. These plants further improve the habitat and help the adaptation of larger vascular plants like shrubs, or even medium- or large-sized trees. More animals are then attracted to the place and finally a climax community is reached.

2.     Secondary succession

Succession that follows disruption of a pre-existing community is called secondary succession. (e.g. Forest fire, harvesting, hurricane) that reduces an already established ecosystem (e.g. a forest or a wheat field) to a smaller population of species, and as such secondary succession occurs on preexisting soil whereas primary succession usually occurs in a place lacking soil.

5.     Explain Food chains, food webs and ecological pyramids?

Food Chains:

Food chains were first introduced by the African-Arabic scientist and philosopher Al-Jahiz in the 9th century but got popularized by Charles Elton in the year 1927.

It is defined as an order of living organisms in a community in which continuous consumption of one organism by other organism and so on takes place.

It can be stated as a chain of organisms in their natural surroundings, through which energy is transferred.

Food Web:

A food web may be defined as a graphical representation depicting interconnection between various food chains.

.

As a food web contains a number of interconnected food chains, hence it results in a complex structure.

Whenever various food chains form such a structure by overlapping each other, it results in generation of a Food Web.

A complex food web

6.     Explain different types for ecosystem?

Forest ecosystem

A terrestrial environment consisted and dominated by trees growing in a closed system is called as a forest.

So, a scientific study of interrelated processes, patterns of flora, fauna and their surroundings in a forest is stated as Forest Ecosystem.

• Case: Chunati Wildlife Sanctuary (CWS), Bangladesh

     Forest Resource Collection is the significant employment choice for larger part of the individuals living in or around the Chunati Wildlife Sanctuary (CWS), Bangladesh.

     The study helped to identify the nature and sorts of forest resources, their collection and quantification in order evaluate the value of the amount of forest resources collected by different resource collectors.Market based approach was being used to estimate the value of the collected resources. Interviews of the resource collectors and multiple checking of the selling price of that particular resource from the adjacent local markets was criteria used for it

     A total of 28 forest trails (used by the local communities as entry or exit points for forest resource collection) out of 56 were selected proportionately from two forest ranges (12 from Chunati and 16 from Jaldi) and from all categories of forest trails based on frequency of use (heavily used, moderately used and less used) for the study.

     The survey was conducted during the dry season (October to May) as it is found to be suitable for resource collection compared to wet season (June to September).

     Result of the study shows that 481 resource collectors per day enter into the CWS through surveyed trails before noon and get back before evening of which 22% are female. Higher numbers of resource collectors were found to carry fuel wood (30%) followed by NTFP or fruits (13%), timber (11%), agricultural products (11%), bamboos or bamboo shoots (10%), sungrass (10%), etc.

     The mode of carrying forest resources was by shoulder load (63%) followed by head load (30%). Among the resource collectors 84% are adult and the rest 16% are minor. The resource collectors spend 5.71 hours per day on average at the forests to collect resources and travel 6.41 km on average for each visit to the CWS.

     The average value of the resources collected by each collector on each visit is BDT 301 (USD 3.71) which may be calculated as BDT 289,735 (USD 3,697.16) for the whole of CWS per day.

     The findings of this study will give a better insight to the problem of forest degradation in Bangladesh and particularly in the CWS.

b)  Grassland ecosystem

A grassland ecosystem is one which is dominated by non woody (herbaceous) plants and various types of grass.

• Case: Grassland of Middle South Inner Mongolia

     In this study, we analyse the changes of indicators of ecosystem services and functions, in order to understand the main cause of grassland degradation due to climatic variation or land use changes in the middle-south Inner Mongolia.

     The soil nutrient and the water supply of supporting service got recovery during 1988–2008. The loss of net primary production declined, and the quality of the retained unconverted grassland (RUG) even increasingly degraded from 2000 to 2008.

     Analytical results show that environmental degradation on the land-use-changed-area is lower than that on the RUG from 2000 to 2008. It illustrates that climatic variation has more negative impacts on grassland ecosystem service, and which is significantly higher than the so-called “overgrazing” induced grassland degradation.

     Moreover, it cannot be excluded that those species died out on the RUG due to natural selection or competitive evolution in an evolutionary process under the deteriorative weather condition rather than overgrazing.

     The positive impacts of human activities such as conservation programs and wildlife protection laws also benefit to regional grassland ecosystem obviously in the study area, so that can delay the environmental degradation even if each planet has its life cycle.

     It indicates that an integrated regional planning involving the considerations of climatic conditions, geographical characteristics, socioeconomic factors, and ecological functions and biodiversity can benefit to regional grassland conservation based on monitoring and management via scientific methods

c)  Desert ecosystem

A desert is a barren land of landscaping area with very little precipitation (rain), lack of vegetation and very hostile living conditions for plant and animal life.

Case: The Western Desert, USA

     The western desert covers an area of over 2 lacs sqkms in south-west USA.

     It has 03 sub-deserts: Mojave, Chihuhuan and Sonoran.

     It extends in the states of Arizona & California (USA) and some parts of New Mexico too.

     Major Extractions done in this region are: Coal, Copper, Uranium, etc.

     Due to its solar potentiality, it has a huge capacity to generate solar electricity.

     Some oil reserves are also found here.

     Peppers and grapes are few farming crops found in this region.

     With around 30 million tourists per year, tourism is a key indicator of its economy.

Some challenges that are being faced in Wester Desert are as follows:

     Extreme Temperature

     Inaccessibility due to its vastness

     Inadequate water supply

     Very low rainfall

Hoover Dam, constructed on Colorado River is playing a crucial resource for counteracting irrigation and drinking problems.

d)  Aquatic ecosystem (ponds, streams, lakes, rivers, oceans, estuaries)

‘Aqua’ means ‘water’. Hence, an ecosystem present in a body of water is called an Aquatic Ecosystem.

Types of Aquatic Ecosystems:

1)     Freshwater Ecosystem

2)     Marine Ecosystem

3)     Transitional Communities

Classification of Aquatic Ecosystem

7.     Define biodiversity?

Biodiversity: Bio = Diversity = Variety

The term Bio-Diversity was first coined by Walter G. Rosen in 1986. Biodiversity, refers to the variety of life on Earth. It includes diversity of ecosystems, species and genes, and the ecological processes that support them. Everything that lives in an ecosystem is part of the web of life, including humans. Each species of vegetation and each creature has a place on the earth and plays a vital role in the circle of life. Plant, animal, and insect species interact and depend upon one another for what each offers, such as food, shelter, oxygen, and soil enrichment. Maintaining a wide diversity of species in each ecosystem is necessary to preserve the web of life that sustains all living things.

There are three levels of Diversity

• Species diversity
• Genetic diversity
• Ecosystem or Habitat diversity

Species diversity:  The species diversity peaks in the tropical forest and coral reefs. India has around 2,00,000 species of the total species described.It is defines as variety of different species of living forms in a given area.

Genetic diversity:   These variations help the individuals to have a variant that help it to be suite for the new environment. The more genetic diversity in a population, the more chances in variations.

Ecosystem or Habitat diversity: Ecosystem is the structural and functional unit of the biosphere. Ecosystem diversity is defined as „the aggregation of various habitats, community types and abiotic environment in a given area‟.  India has one of the richest ecosystem diversities, ranging from deserts, plains, hills, mangroves, rainforests to cold Himalayas. Out of the 18 hot spots of biodiversity recognized in the world, India has two of them, Eastern Himalaya and The Western Ghats. Eastern Himalayas is recognized as the “Cradle of Speciation” due to rich diversity of primitive flowering plants.

8.     Describe Bio geographical classification of India?

India has different climate and topography in different parts and hence is termed as a mega diversity country. India occupies 10th place among plant rich countries of the world. It is essential to acquire knowledge about the distribution and environmental interaction of flora and fauna of India.

Bio-geographers have classified India into ten Bio-geographic zones with each zone having characteristic climate, soil and biodiversity.

Our country can be conveniently divided into ten major regions, based on the geography, climate and pattern of vegetation seen and the communities of Mammals, Birds, Reptiles, Amphibia, Insects and other Invertebrates that live in them.

• Trans Himalayan Region of Laddakh
• The Himalayan Ranges
• The Terai
• The Gangetic and Brahmaputra Plains
• The Thar Desert of Rajasthan
• The semi arid grassland region of the Deccan plateau Gujarat, Maharashtra, Andhra Pradesh, Karnataka and Tamil Nadu
• The Northeast States of India
• The Western Ghats
• The Andaman and Nicobar Islands
• Western and Eastern Coastal Belt

9.     Explain Consumptive use, productive use?

Various uses of biodiversity regarding direct and indirect values are as follows:

1. Timber

Wood is one of few commodities used and traded worldwide that is mainly harvested from wild sources. It is also one of the economically most important commodities in national and international trade. Wood export constitutes a significant part of the export earnings of many tropical developing countries. Malaysia, Papua New Guinea and Indonesia are among the major exporters of hardwoods, including prized timbers such as teak and mahogany, produced mainly from natural forests.

2.     Fishery

Fish and other fishery products make up another class of commodities of great economic importance in international trade that are harvested mainly from wild sources. These resources are also of crucial importance to global food security. Annual landings of aquatic resources have increased nearly five-times in the past four decades; and more than 80% was harvested from marine capture fisheries, the remainder was from inland fisheries and from aquaculture, both inland and marine. Though there are over 22,000 species of fish, but just ten individual marine fish species make up one-third of marine capture landings. The most important are the herrings, sardines and anchovies group.

3.     Food

Food plants exemplify the most fundamental values of biodiversity. Presently, around 200 species have been domesticated as food plants. Out of these about 15 to 20 are of major international economic importance.

4.     Medicinal value

Living organisms provide us with many useful drugs and medicines. Digitalis, an important drug in the treatment of certain heart ailments, comes from a small flowering plant – purple foxglove; Penicillin is a derivative of fungus; and so on. The UNDP estimates the value of pharmaceutical products derived from Third World plants, animals and microbes to be more than $30 billion per year.

There are numerous organisms that may produce useful medical compounds that are as yet unknown and untested. For instance coral reefs offer a particularly promising use in pharmaceutical drugs, because many coral reef species produce toxins to defend themselves. Many plant species native to India such as Neem, Tulsi, etc. too have potential medicinal applications.

5.     Genetic value

Biological diversity is a valuable genetic resource. Most of the hybrid varieties of crops under cultivation have been developed by incorporating useful genes from different species of plants to produce better quality of the product with longer self-life or having better resistance to pests. Though such breeding techniques are unlimited in scope; but, for getting better strains in future, it is essential to build-up a gene-pool because the quality, yield, and resistance to pests, disease and adverse climatic conditions mostly depend on genetic factors and combination of genes which may be different in different strains/ varieties of species. There are hundreds of examples which illustrate how genetic modification helped in improved quality of the product. A few of them are mentioned as under:

The genes from a wild variety of melon grown in U.P. Helped in imparting resistance to powdery mildew in musk-melons grown in California (USA).

The genes from the Kans grass (Saccharum Spontaneium) grown in Indonesia helped in imparting resistance to red rot disease of sugarcane.

A wild variety of rice from U.P. Saved millions of hectares of paddy crop from Grossy-Stunt virus.

6.     Tourism

Tourism industry is mainly based on observation of wildlife within protected areas and is a major source of income for many developing countries. Tourism is the major source of foreign income for Kenya. Eco-tourism is now getting more attention and it includes interest in the all species of plants and animals, and forests.

7.     Poor and indigenous people

Poor and indigenous people of under-developed countries are dependent on diversity in forests and wildlife for food, shelter, tools, and materials for clothing and medicines. Further reduction in the biodiversity can further increase the poverty of these poor people.

8.     Pollution control

Plants and certain micro-organisms in particular can remove toxic substances from the air, water and soil. Since the different species have different characteristics and capabilities, therefore, a diversity of species can provide wide range of pollution control. For example, toxins like carbon-di-oxide and sulphur-di-oxide are removed by vegetation; carbon-monoxide is controlled by soil fungi and bacteria.