Explore topic-wise InterviewSolutions in .

(b) Detritus food chain

Decomposition is controlled by

(i) Chemical composition of detritus

• Decomposition is faster when detritus is rich in nitrogen and water soluble substances like sugars.
• Decomposition is slow, when detritus is rich in lignin and chitin.

(ii) Temperature and soil moisture, through their effects on the activities of microbes.

• Warm and moist environment favour decomposition.
• Low temperature and absence/reduced moisture levels inhibits decomposition.

(iii) Oxygen

• Decomposition is an oxygen consuming process
• Anaerobic condition inhibits decomposition.

• Certain organisms of the GFC are predators to certain animals of DFC. As a result the food chains become interconnected.
  eg. earth worms which are detrivores are eaten by small birds (DFC) which become prey to vultures/kites or even cats of the GFC.
• Organisms like cockroaches and cows, which are omnivores play an important role in the interconnections of food chain constitute a food web.

DFC and GFC are interlinked at same level in the terrestrial ecosystem, energy flow occurs via DFC then GFC . DFC can be connected to GFC at some level as source of organisms of DFC are prey to GFC animals.

(c) Anabolism

1. Pond ecosystem 

2. Forest ecosystem.

(a) Nitrogen cycle

A graphical representation of the amount of organic material (biomass) present at each successive trophic level in an ecosystem is called pyramid of biomass.

Correct Answer is: (c) i and ii

1. Act as bridge between sea and rivers by balancing sedimentation and soil erosion. 

2. Help to reduce water force during cyclones, tsunamis and high tide periods. 

3. Help in wind break, O₂ production, carbon sequestration and prevents salt spray from waves.

Reed-swamp stage, phytoplankton stage, shrub stage, submerged plant stage, forest stage, submergedfree floating stage and marsh medow stage.

(1) Phytoplankton stage – It is the first stage of succession consisting of the pioneer community like blue green algae, green algae, diatoms, bacteria, etc., The colonization of these organisms enrich the amount of organic matter and nutrients of pond due to their life activities and death. This favors the development of the next serai stages.

(2) Submerged plant stage – As the result of death and decomposition of planktons, silt brought from land by rain water, lead to a loose mud formation at the bottom of the pond. Hence, the rooted submerged hydrophytes begin to appear on the new substratum. 

Example: Vallisneria and Hydrilla etc. The death and decay of these plants will build up the substratum of pond to become shallow.

(3) Submerged free floating stage – During this stage, the depth of the pond will become almost 2-5 feet Hence, the rooted hydrophytic plants and with floating large leaves start colonising the pond.

Example: Rooted floating plants like Nelumbo, Nymphaea and some free floating species like Azolla, and Pistia are also present in this stage. By death and decomposition of these plants, further the pond becomes more shallow.

(4) Reed-swamp stage – It is also called an amphibious stage. During this stage, rooted floating plants are replaced by plants which can live successfully in aquatic as well as aerial environment.

Example: Typha, Phragmites, Sagittaria and Scirpus etc. At the end of this stage, water level is very much reduced, making it unsuitable for the continuous growth of amphibious plants.

(5) Marsh meadow stage – When the pond becomes swallowed due to decreasing water level, species of Cyperaceae and Poaceae colonise the area. They form a mat-like vegetation with the help of their much branched root system. This leads to an absorption and loss of large quantity of water. At the end of this stage, the soil becomes dry and the marshy vegetation disappears gradually and leads to shurb stage.

(6) Shrub stage – Here areas are invaded by terrestrial plants like shrubs (Salix and Comus) and trees (Populus and Alnus). These plants absorb large quantity of water and make the habitat dry. Further, the accumulation of humus with a rich flora of microorganisms produce minerals in the soil, ultimately favouring the arrival of new tree species in the area.

(7) Forest stage – It is the climax community of hydrosere. A variety of trees invade the area and develop any one of the diverse type of vegetation.

Example.Temperate mixed forest (Ulmus,Acer and Quercus), Tropical rain forest (Artocaipus and Cinnamomum ) and Tropical deciduous forest (Bamboo and Tectona)

(b) Conductivity

Correct Answer is: (b) Odum

(b) latitude, altitude, direction of mountain and aptitude

Primary productivity depends on

• The photosynthetic capacity of the plant species.
• Availability of nutrients
• Amount of sunlight available
• Water availability and temperature.

The pitcher plant is an insects are however it is chlorophyllous and is thus capable of carrying out the photosynthesis for synthesizing its own food. In this way it acts a producer.

(a) low stability and high resilience

 The different steps involved in the process of decomposition of detritus are as follows : 

(i) Fragmentation 

(ii) Leaching 

(iii) Catabolism 

(iv) Humification 

(v) Mineralization

Fragmentation : Breakdown of detritus into smaller particles. e.g., earthworm. 

Leaching : Water soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts. 

Catabolism : Bacterial and fungal enzymes degrade detritus into simpler inorganic substances.

Humification : It leads to the accumulation of a dark coloured amorphous substance called humus that is highly resistant to microbial action and undergoes decomposition at an extremely slow rate.

Mineralisation : The humus is further degraded by some microbes and release inorganic substances by this process.

(c) Decreases the caloric value in successive trophic levels

Humification leads to break down of complex organic matter and accumulation of humus in the form of a dark a morphous substance in soil. 

Mineralisation is a process in which humus is degraded by microbes to release inorganic nutrients.