Ecosystem VBQs Class 12 Biology

VBQs for Class 12

VBQs Ecosystem Class 12 Biology with solutions has been provided below for standard students. We have provided chapter wise VBQ for Class 12 Biology with solutions. The following Ecosystem Class 12 Biology value based questions with answers will come in your exams. Students should understand the concepts and learn the solved cased based VBQs provided below. This will help you to get better marks in class 12 examinations.

Ecosystem VBQs Class 12 Biology

Very Short Answer Type Questions

Question. What does ‘R’ represent in the given equation for productivity in an ecosystem ?
GPP — R = NPP.
Answer :
 ‘R’ represents the loss of biomass due to respiration. 

Question. Write the equation that helps in deriving the net primary productivity of an ecosystem.
Answer :
 NPP = GPP – R
where, NPP : Net Primary Productivity.
GPP : Gross Primary Productivity.
R = Respiratory losses.

Question. What is secondary productivity? 
Answer :
 Secondary productivity refers to the rate of formation of new organic matter by the consumers specially by the herbivores or primary consumers.

Question. All primary productivity is not available to herbivore. Give one reason.
Answer :
 All primary productivity is not available to a herbivore because a considerable amount of it is utilized by the plants itself in respiration. 

Short Answer Type Questions

Question. How are productivity, gross productivity, net primary productivity and secondary productivity interrelated ?
Answer : 
Productivity is the rate of production of biomass at any trophic level at any given interval of time.
Gross productivity : It is the rate of production of organic matter by green plants per unit time per unit area. On the other hand we can say that it is the total amount of productivity.
Net Primary Productivity : It is the difference between gross primary productivity and the loss due to respiration.
Secondary Productivity : It is rate of production or formation of new organic matter by consumers especially the consumers of the first order or herbivores. 

Question. Explain primary productivity and the factors that influence it.
Answer :
 Primary productivity is the amount of biomass produced per unit area over a time period by green plants during photosynthesis. The factors that influence it are the plant species of the area, their photosynthetic activity, availability of nutrients, solar radiations, precipitation, soil types and the various environmental factors. 

Question. Describe how oxygen and chemical composition of detritus control decomposition ?
Answer :
Decomposition of detritus is an oxygen requiring process i.e. it takes place under aerobic condition in the presence of oxygen. Chemical composition of detritus affects decomposition. Detritus which is rich in nitrogen and water soluble substances decomposes rapidly whereas the detritus having chitin and lignin decomposes at a very slow rate.

Question. Describe the inter-relationship between productivity, gross primary productivity and net productivity.
Answer :
Productivity is the rate of biomass production per unit area over a period of time, Gross primary productivity is the rate of production of organic matter during photosynthesis in an ecosystem.
Net productivity is the gross primary productivity minus respiration losses (R). 
Answer :

Long Answer Type Questions 

Question. Describe the process of decomposition of detritus under the following headings:
Fragmentation; leaching; catabolism; humification and mineralisation. 
Explain the different steps involved in the process of decomposition of detritus.
Answer :
The process of breaking down complex organic matter into inorganic substances like—CO2, water and nutrient is called decomposition. The raw materials for decomposition is called detritus.
They are dead remains of plants and animals.
Steps of decomposition :
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.

Question. Citing lake as an example of a simple aquatic ecosystem, interpret how various functions of this ecosystem are carried out. Make a food chain that is functional in this ecosystem.
Answer :
The components of lake ecosystem (viz : abiotic components, biotic components, consumers of various order and decomposers) function as an unit for various function of ecosystem as follows—
(i) Productivity—conversion of inorganic into organic material with the help of solar energy by the autotrophs. 
(ii) Energy flow—unidirectional movement of energy towards higher trophic level (and its dissipation and loss as heat to the environment). 
(iii) Decomposition—fragmentation, leaching, catabolism, humification, mineralization by bacteria, fungi and flagellates (abundant at the bottom of lake). 
(iv) Nutrient cycling—decomposition of dead matter to release the nutrients back to be reused by the autotrophs. 
Food chain in aquatic ecosystem (lake):
Phytoplanktons ⇒ Zooplanktons ⇒ Small fish ⇒ Big fish.