Ans: C

Exp:

Mangroves ecosystem 

• Mangroves are littoral plants like trees and bushes having exceptional capacity for salt water tolerance (Halophytic adaptability), growing below high-water level of spring tides. Hence, option 1 is correct.
• They have ability to absorb fresh water from saline water and require high solar radiation
• Mangroves also produce pneumatophores/blind roots to overcome respiratory problems. Hence, option 2 is correct.
• They have adventitious roots, also called stilt roots or prop roots. As with banyan trees, certain mangrove species have roots that branch off from stems and branches and encroach on the ground a distance from the main stem. They are known as stilt roots due to their outward appearance and the fact that they serve as the major physical support for these. Hence, option 3 is correct.
• The Mangroves have lot of ecological and local benefits for communities as they:
  • Reduce inundation and moderate monsoonal tidal floods.
  • Prevent coastal soil erosion and enhance nutrient recycling.
  • Source of firewood, medicinal plants and edible plants to locals.
  • Provides employment opportunities.

Ans: D

Exp:

Ecosystems are classified as Natural ecosystems and Man-made ecosystems.

• Natural ecosystems: They are totally dependent on solar radiation E.g. forests, grasslands, oceans, lakes, rivers and deserts. They provide food, fuel, fodder and medicines. Certain ecosystems depend on solar radiation and energy subsidies (alternative sources) such as wind, rain and tides. e.g tropical rain forests, tidal estuaries and coral reefs.
• Man made ecosystems: Those which are dependent on solar energy-e.g. Agricultural fields and aquaculture ponds. Those dependent on fossil fuel e.g. urban and industrial ecosystems.

Ans: B

Exp:

Statement 1 is correct: The term ‘Biosphere’ was given by geologist Edward Suezz in 1875. The biosphere is absent at extremes of the north and south poles. Occasionally spores of fungi and bacteria do occur at heights beyond 8000 mts, but they are not metabolically active and represent only the dormant life.

Statement 2 is incorrect: Recently, the term ecosphere has been used more commonly. It is used to denote the biosphere (living components) along with its three abiotic components –atmosphere, hydrosphere and lithosphere of the earth as one entity (unit). Ecosphere = Biosphere + Lithosphere + Hydrosphere + Atmosphere.

Statement 3 is correct: The global environment consists of three main subdivisions:

• The hydrosphere, which includes all the water components,
• The lithosphere comprises the solid components of the earth’s crust, and
• The atmosphere formed from the gaseous envelope of the earth. The biosphere consists of the lower atmosphere, the land and the oceans, rivers and lakes, where living beings are found.

It has both living and nonliving components, which are interdependent and interrelated in terms of their structure, components, and functioning.

Ans: B

Exp:

Ecological efficiency : In an ecosystem the amount of energy decreases at each subsequent trophic level because at each trophic a part of the available energy is lost in respiration or used up in metabolism.

• A part of energy is lost at each transformation, i.e. when it moves from lower to higher trophic level as heat.

• It is the ratio between the amount of energy acquired from the lower trophic level and the amount of energy transferred from higher trophic level is called ecological efficiency.

• Lindman in 1942 defined these ecological efficiencies for the 1st time and proposed 10% rule

• • E.g. if autotrophs produce 100 cal, herbivores will be able to store 10 cal. and carnivores 1 cal. However, there may be slight variations in different ecosystems and ecological efficiencies may range from 5 to 35%.

Ans: A

Exp:

Statement 1 is incorrect: There is unidirectional flow of energy in the food chain from sun to producers and then to a series of consumers of various types. Thus, a food chain is always straight and proceeds in a progressing straight line.

Statement 2 is incorrect: The important point to note is that the amount of energy decreases at successive trophic levels. Usually 80 to 90% of potential energy is lost as heat at each transfer on the basis of the second law of thermodynamics (transformation of energy involves loss of unavailable energy).

Statement 3 is correct: There is repeated eating at each trophic level in the food chain in which each group eats the smaller one and is eaten by the larger one at the next trophic level. Thus, it involves a nutritive interaction between the biotic components of an ecosystem. Any organism that dies is transformed into detritus or dead biomass, which is used as a fuel source by decomposers. For their energy needs, organisms at each trophic level rely on those at the lower trophic level.