Class 12th Biology 2011 Set3 Delhi Board Paper Solution
Question 29
(a) Explain primary productivity and the factors that influence it.
(a) Explain primary productivity and the factors that influence it.
(b) Describe how oxygen and chemical composition of detritus control decomposition do.
OR
(a) What is El Nino effect? Explain how it accounts for biodiversity loss.
(b) Explain any three measures that you as an individual would take, to reduce environmental pollution.
Answer
a) Primary productivity is influenced by some physical features as –
Light intensity
Light duration
Temperature
Soil pH
Availability of nutrients
CO2 levels
While other features influencing NPP is the presence of biomass per unit area over a given time period by plants during photosynthesis is defined as primary productivity It is expressed in term of weight (g ) or energy (Kcal m ). Productivity can be categorized into gross primary productivity (GPP) and net primary productivity (NPP).
GPP is the production rate of organic matter at the time of photosynthesis.
Primary productivity is directly proportional to the amount of carbon dioxide, sunlight and water and is inversely proportional to respiratory losses.
It can be expressed as -
NPP = GPP - Respiratory losses (R)
b) Consumption of oxygen is elementary step for decomposition which is directly related to the amount of oxygen in the atmosphere. Chemical nature of detritus and climatic condition regulates consumption of oxygen.
Rate of decomposition deceases if detritus is richly supported by lignin or chitin meanwhile its rate increases if detritus is supplied with nitrogen and sugar.
OR
a) Earth is being heated up day by day because of global warming. There has been an increase of 0.6 oC in overall temperature of earth. This fluctuation in earth temperature is leading to some hazardous changes displaying odd climatic variations, increased melting of polar ice cap and Himalayan zones. These types of changes are defined as El Nino effect.
El Nino effect – it can be defined as the increase or prolong warming of sea surface as compared to the normal sea temperature. It results in the elevation in sea level submerging coastal areas an active research topic.
Loss of biodiversity
Deforestation – increase in the level of CO2 concentration leads to decreased biomass, loss of habitat, disturbs hydrologic cycle, soil erosion etc.
b) Pollutants are those physical, chemical or biological molecules which get into the air and bring about undesirable change in air, water or soil. Government of India in 1986 passed environmental protection act. Action of pollutant depends upon the exposure, duration and concentration of pollutant.
Measure to reduce environmental pollution -
1. Use of electrostatic precipitator, for capturing the pollutant coming from thermal industry, it can capture around 99 % of the pollutant.
2. Use of unleaded petrol in motor vehicles, and supplementing vehicle with Catalytic converters so that unburned hydrocarbons are converted into CO2 and water while carbon monoxide and nitric oxide are converted into CO2 and nitrogen gas.
3. Use of CNG in motor vehicles.
4. Damping of waste in soil.
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