This document discusses primary and secondary productivity. It defines productivity as the rate of production in a system. Primary productivity is the rate at which radiant energy is converted to organic substances through photosynthesis and chemosynthesis by producers. It is classified into gross, net, and net community productivity. Secondary productivity is the rate at which food energy is assimilated by consumers. It is lower than primary productivity and decreases with each trophic level as much energy is lost as heat. The key difference between primary and secondary productivity is that primary productivity is the rate of synthesis of organic matter by producers, while secondary productivity is the rate of synthesis by consumers through assimilation of food energy.

1. PRODUCTIVITY
DILSHANA FATHIMA
M.Sc. BIOCHEMISTRY

2. INTRODUCTION
 The term productivity is used to denote the
amount of accumulated organic matter in a given
time.
 The term productivity represents the rate of
production in a system.
 The productivity can be classified into 2
1. Primary productivity
2. Secondary productivity

3. PRIMARY PRODUCTIVITY
 It is the rate at which radiant energy is converted
by photosynthetic & chemosynthetic activity of
producers to organic substances.
 i.e, the rate of accumulation of dry matter by the
plants through photosynthesis & chemosynthesis.
 It is expressed in terms of gm/m²/day.
 It is further classified into 3
a) Gross primary productivity
b) Net primary productivity
c) Net community productivity

4. a) Gross primary productivity (GPP)
o The rate of total capture of energy/the rate of total
production of organic material.
o Is the total rate of photosynthesis including the
organic matter used up in respiration during the
measurement period.
o It is the total amount of food energy formed in a
given time during photosynthesis.
b) Net primary productivity (NPP)
o It is the rate of storage of organic matter in plant
tissues exceeding the respiratory use by plants
during the period of measurement.

5. o The balance energy/biomass remaining after
meeting the cost of respiration of producers is
called NPP.
NPP = GPP – Respiration rate
o NPP results in the accumulation of plant biomass,
which serves as the food of herbivores &
decomposers.
c) Net community productivity (NCP)
o It is the rate of storage of organic matter not used
by heterotrophs during the period under
consideration.
NCP = NPP – Heterotrophic consumption

6. SECONDARY PRODUCTIVITY
 The rate at which food energy is assimilated at the
trophic level of consumer.
 The primary producers have produced the food of
consumers & secondary productivity reflects only the
utilization of this food for production of consumer
biomass.
 The primary consumer takes in chemical potential
energy in the form of food from plants.
 Most of it dissipates in the form of heat & is lost out
of the ecosystem.
 Only a small part of energy is fixed in the form of
chemical potential energy in the protoplasm.

7.  The same process is repeated at the secondary
consumers or the primary carnivorous levels & so on.
 Hence, at each step of energy transfer from 1 trophic
level to another, a large amount of energy is degraded
into heat & never returns to the ecosystem.

8. DIFFERENCE
PRIMARY
PRODUCTIVITY
SECONDARY
PRODUCTIVITY
 Rate of synthesis of
organic matter by
producer.
 Comparatively quite
high.
 Due to synthesis of fresh
organic matter from
inorganic raw material by
producers.
 Rate of synthesis of
organic matter by
consumers.
 It is small & decreases
with rise of trophic level.
 It is due to assimilation of
food energy at consumers
trophic level.

9. THANK YOU