Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Primary production is defined as the amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis. It is expressed in terms of weight () or energy ().
Gross Primary Productivity () is the rate of production of organic matter during photosynthesis. A considerable amount of is utilized by plants in respiration ().
Net Primary Productivity () is the available biomass for the consumption of heterotrophs (herbivores and decomposers). It is calculated as .
Secondary productivity is defined as the rate of formation of new organic matter by consumers.
Decomposition is the process where decomposers break down complex organic matter into inorganic substances like , , and nutrients.
The raw material for decomposition is called detritus, which includes dead plant remains (leaves, bark, flowers) and dead remains of animals including fecal matter.
The process of decomposition involves five steps: Fragmentation, Leaching, Catabolism, Humification, and Mineralization.
Fragmentation: Detritivores (e.g., earthworms) break down detritus into smaller particles.
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 leads to the accumulation of a dark-colored amorphous substance called humus, which is highly resistant to microbial action and undergoes decomposition at an extremely slow rate.
Mineralization: The humus is further degraded by some microbes and release of inorganic nutrients occurs.
Decomposition is an oxygen-consuming process. It is slower if detritus is rich in lignin and chitin, and quicker if detritus is rich in nitrogen and water-soluble substances like sugars.
📐Formulae
💡Examples
Problem 1:
In a tropical rainforest, the Gross Primary Productivity () is measured at . If the respiration loss () by the primary producers is , calculate the Net Primary Productivity ().
Solution:
Explanation:
The Net Primary Productivity is the actual organic matter available for the next trophic level after accounting for the metabolic energy used by the producers themselves.
Problem 2:
Explain why decomposition of fallen leaves is faster in a warm and moist environment compared to a cold and dry environment.
Solution:
Temperature and soil moisture are the most important climatic factors that regulate decomposition through their effects on the activities of soil microbes. Warm and moist environment favors the growth and enzymatic activity of aerobic microbes, whereas low temperature and anaerobiosis inhibit decomposition.
Explanation:
Chemical kinetics and biological enzyme activities are temperature-dependent. values in biology suggest that metabolic rates often double with every rise in temperature up to an optimum level.