Question

What is primary productivity? Give brief description of factors that affect primary productivity.

Answer 1

RATE OF BIOMASS PRODUCTION IS CALLED PRODUCTIVITY.PRIMARY PRODUCTIVITY IS THE PRODUCTION OF BIOMASS BY THE PROCESS OF PHOTOSYNTHESIS.TEMPERATURE AND MOISTURE EFFECT THE GROWTH OF PRIMARY PRODUCTIVITY.

Answer 2

Answer:

Explanation:  Ans. The rate of synthesis of organic matter, or biomass produced at any trophic level

during a given period of time is called productivity. For productivity three things are

necessary – (i) Rate of production, (ii) Per unit area and (iii) Unit time. Productivity is

of two types– (1) Primary productivity and (2) Secondary Productivity. It is measured

as weight (Ex- g/m2

/yr) or energy (Ex-Kcal/m2

/yr).

Primary Productivity – Primary productivity 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 (g–2) or energy (K cal m–2). It can be

divided into two types – (a) gross primary productivity and (b) net primary

productivity.

(a) Gross Primary Productivity – Gross primary productivity of an ecosystem is

the rate of production of organic matter during photosynthesis. A considerable

amount of GPP is utilised by plants in respiration. It is equal to addition weight

of stored organic material present in body of producer and loss during different

activity happens in its body.

(b) Net Primary Productivity – Net primary productivity is the available biomass

for the consumption to heterotrophs (herbivores and decomposers). Gross

primary productivity minus respiration losses (R), is the net primary

productivity (NPP).

G.P.P – R = N.P.P.

Primary productivity depends on the plant species inhabitating a particular

area. It also depends on a variety of environmental factors, availability of nutrients

and photosynthetic capacity of plants. Therefore, it varies in different ecosystems. The

annual net primary productivity of the whole biosphere is approximately 170 billion

tons (dry weight) of organic matter. Of this, despite occupying about 70 percent of the

surface, the productivity of the oceans are only 55 billion tons.