Wednesday, September 18, 2013

Important questions-ii

Write briefly about the biogeographical zones in India
There are 10 biogeographical zones in India. They are briefly described below:
  1. Trans-Himmalayas: The Trans-Himmalayas is an extension of the Tibetean plateau.
  2. Himalayas: The Himalayas form the northern boundary of India. The Himalayas comprises a diverse range of biotic provinces and biomes.
  3. Desert: Three kinds of deserts are found in India. They are, Desert of western Rajasthan, Desert of Gujarat and the high altitude cold desert of Jammu & Kashmir and Himachal Pradesh
  4. Semi-arid: This zone lies in between the desert and the Deccan plateau.
  5. Western Ghats: This is a mountain range that runs along the western coast of India. This ghat section covers a diverse range of biotic provinces and biomes.
  6. Deccan Plateau: It is a large triangular plateau south of Narmada valley. The Satpura mountains cover the north side, western ghats and eastern ghats cover the west and east sides respectively. The plateau slopes towards east. The plateau is covered with deciduous vegetation.
  7. Gangetic plain: The Gangetic plains cover from south of the Himalayas to north of tropic of cancer. These plains were formed by the Ganges river system and are relatively homogenous. The famous 'sunderban' forests are located in these plains.
  8. North-east India: The plains and non-himalayan hill ranges of northeastern India fall in this zone. This zone is filled with a wide variety of vegetation.
  9. Islands: The Andaman and Nicobar islands in the bay-of-bengal is a group of 300 small and large islands. Mostly tribes live in Nicobar islands. These islands have a highly diverse set of biomes.
  10. Coasts: The Indian subcontinent is blessed with a long coastline on the east and west with distinct differences between the two.

Write notes on threats to biodiversity
Biodiversity has evolved simultaneously with human culture. Man has met the changing needs and pressures of increasing population by applying knowledge and skills. People have hunted, fished and gathered species for food, fuel, fiber and shelter thereby eliminating competing or threatening species.
Activities mentioned above destroys and depletes the basis of an ecosystem (genes and species). As a result, mankind loses food, medicine and industrial products in the present and future.
According to the World Conservation Union's Red List, the threat to biodiversity is due to human activity particularly, habitat destruction.
Few of the Major biodiversity threats are listed below:
  1. Habitat destruction
  2. Extension of agriculture
  3. Filling-up of wetlands
  4. Conversion of rich biodiversity site for human settlement and industrial development
  5. Destruction of coastal areas
  6. Uncontrolled commercial exploitation
One of the primary causes of loss of biodiversity is habitat destruction. The main causes for the same are listed below:
  1. Agricultural activities
  2. Extraction including mining, fishing, logging and harvesting
  3. Developmental activities including human settlement, industry and associated infrastructure
Millions of hectares of forest area is lost due to illegal encroachment of forest land. Forest land is also lost due to construction of river valley projects, introduction of transmission lines and roads, etc. Change in forest composition and quality can lead to decline in primary food species for wildlife.
Fragmentation is the process of division of a population into several small groups. Habitat loss and fragmentation leads to formation of isolated, small and scattered populations which are susceptible to inbreeding, depression, high infant mortality and eventually possible extinction.
Introduced species are responsible for many recorded species extinctions, especially on islands. In these isolated ecosystems, a new predator, competitor or pathogen can rapidly endanger species that did not evolve simultaneously with the newcomer.
Several forest, fisheries and wildlife resources have been over-exploited to the point of extinction. A few cases are mentioned below as a point in case. Poaching of wild animals (The Tiger, Elephant, Rhinoceros) has resulted in their extinction. Population pressures adversely affect the forest resources on which the local communities depend while having a negative impact on biodiversity.
Pollutants strain ecosystems. Contamination affects the food chain. A point in case is marine pollution from non-point sources that ruins estuaries and coastal seas throughout the world. Pesticides used to control agricultural pests have shown to negatively impact birds due to severe air pollution in Spain.

Write about energy flow in an ecosystem
Energy is an essential requirement for all living organisms. Solar energy is the only source of energy for the Earth. Solar energy is transformed to chemical energy by photosynthesis in plants (primary producers). Though lot of sunlight falls on plants, only 1% of this is utilized for photosynthesis.
Some amount of energy is used by the plant for growth and the remaining is transferred to consumers by the process of eating. Thus energy enters the ecosystem through photosynthesis and passes through different feeding levels (tropic levels)
The flow of energy through an ecosystem follows two laws of thermodynamics:
  1. First law of thermodynamics states that “energy can neither be created nor destroyed, but can be converted from one form to another.” Ex: Energy for an ecosystem comes from the sun. It is absorbed by plants where it is converted and stored as chemical energy or solar energy is converted into chemical energy.
  2. Second law of thermodynamics states that “whenever energy is transformed, there is a loss of energy through the release of heat.” Ex: Whenever energy is transferred between tropic levels, loss of energy takes place through respiration, running, hunting, etc.
Describe aquatic ecosystem
Aquatic ecosystem deals with water bodies. Types of organisms found in aquatic environment depend on salinity of water (salt content).
Types of aquatic life zones:
  1. Fresh water life zones (Ponds, Streams, Rivers, Lakes)
  2. Salt water life zones. (Oceans and Estuaries)
Pond ecosystems
  1. Pond is temporary, only seasonal
  2. It is a stagnant freshwater body
  3. It is easily polluted due to limited amount of water.
Structure and function
Examples of abiotic components are temperature, light, water, organic and inorganic compounds.
Biotic components are comprised of
i.              Producers: These include green photosynthetic organisms. They are of two types:
                        a)         Phytoplankton and
                        b)         Microphytes
Phytoplankton are microscopic aquatic plants, which float freely on the surface of water. Examples of phytoplankton are Algae, Volvox, Pandorina, Anabena and Cosmarium.
Microphytes are large floating plants and submerged plants. Examples of microphytes are hydrilla, jussiaea, wolfia and demna.

            ii.         Consumers:
                        Primary consumers (Zooplanktons): These are microscopic animals that freely float on                               the surface of water. Zooplanktons are found along with phytoplanktons which they eat.                           Examples of zooplanktons are planktons, very small fish, ciliates, flagellates and                            protozoans.
                        Secondary consumers (Carnivores): They feed on zooplanktons. Examples of carnivores                are insects like water beetles and small fish.
                        Tertiary consumers: They feed on smaller fish. Examples of tertiary consumers are large                 fish like game fish.
iii.        Decomposers: They decompose dead plant and animal matter and their nutrients are          released and reused by green plants. Examples of decomposers are fungi, bacteria and         flagellates.
Lake ecosystems:
i.                                Lakes are natural shallow water bodies
ii.                              Lakes are supplied with water from rainfall, melting snow and streams.
iii.                            Lake is a permanent water body with large water resources.
iv.                            Lakes help in irrigation and supplying drinking water.

Structure and function of Lake Ecosystem: The abiotic components of lake ecosystems consist of temperature, light, proteins, lipids, turbidity, oxygen and carbon-dioxide.
The biotic components are classified into:
                 i.               Producers:             Green plants (Floating, Submerged and amphibious). Examples of                                 producers are phytoplanktons, algae and flagellates.
                  ii.            Consumers:            Primary consumers are zooplanktons like ciliates, protozoans, etc that                                        feed on phytoplanktons.
Secondary consumers  are carnivores like insects and smaller fishes that feed on zooplanktons
                                       Tertiary consumers feed on smaller fish. Examples are large fish and                                                            game fish
iii.     Decomposers:        Decomposers decompose dead plants and animals. Examples of                                                                  decomposers are bacteria, fungi and actinomycetes.

River Ecosystem:
                          i.            It is fresh water and freely flowing water system
                        ii.            Flowing water allows mixing of water resulting in higher dissolved oxygen
                      iii.            River deposits large amount of nutrients.
Structure and function of River Ecosystem: The abiotic components of river ecosystems are temperature, light, pH, nutrients, organic and inorganic compounds.
Biotic components are classified into:
                          i.            Producers:          Phytoplankton, Algae, water grasses, aquatic grasses and other                                               amphibious plants.
                        ii.            Consumers:        Primary consumers feed on phytoplanktons. Examples are water insects,                                snails and fishes.
Secondary consumers are feed on primary consumers.
iii.     Decomposers:        Decomposers decompose dead plants and animals. Examples of                                                                  decomposers are bacteria, fungi and actinomycetes.

Ocean ecosystems:
  1. Oceans occupy a large surface area and made up of saline water.
  2. Commercial activities are carried out in oceans.
  3. Oceans are rich in biodiversity
  4. Oceans moderate the temperature of the earth.
Structure and function of Ocean Ecosystems:
The abiotic components of ocean ecosystems are temperature, light, NaCl, K, Calcium and Magnesium salts and alkalinity.
The biotic components comprise of
  1. Producers: Phytoplanktons (diatoms, unicellular algae, etc) and marine plants (sea weeds, chlorophyceal, phaeophyceae)
  2. Consumers: They are heterotrophic macroconsumers which depend upon producers for their nutrition.
    1. Primary consumers or herbivores feed on producers (Ex: Crustaceans, Mollusks, Fish
    2. Secondary consumers or carnivores feed on herbivores (Ex: Herring, Mackerel, etc)
    3. Tertiary consumers are the top consumers and feed on small fishes. (Ex: Cod, Haddock, etc)
  3. Decomposers decompose dead organic matter. (Ex: Bacteria and fungi)

Estuarine ecosystem:
  1. Estuaries are transition zones that are strongly affected by tides of the sea.
  2. Water in estuaries change periodically
  3. The organisms in estuaries have a wide tolerance
  4. Salinity remains highest in summer and lowest in winter.
Structure and function of Estuarine Ecosystems:
Abiotic components of estuarine ecosystems are temperature, pH, sodium and potassium salts and nutrients.
Biotic components consist of
  1. Producers: Examples are marsh grasses, seaweeds, seagrasses and phytoplankton.
  2. Consumers: Examples are Oysters, Crabs, Seabirds, and small fishes
  3. Decomposers: Examples are Bacteria, fungi and actinomycetes.

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