Ecological pyramids - pyramid of number, pyramid of biomass & pyramid of energy

1. DILSHANA FATHIMA
M.Sc. BIOCHEMISTRY

2. INTRODUCTION
 The concept of ecological pyramids was introduced by
Charles Elton. Thus they are also called Eltonian
pyramids.
 The graphical representation of the trophic structure
(number, biomass etc) & trophic function (energy
transformation at each level) is called ecological
pyramids.
 In the ecological pyramid, the producers form the base &
the final consumer occupies the apex.
 The successive levels b/w producers & the final
consumers form the tiers of the pyramid.

3.  An ecological pyramid may be upright, inverted or spindle
shaped.
 There are 3 types of ecological pyramids
1. Pyramid of numbers
2. Pyramid of biomass
3. Pyramid of energy

4. PYRAMID OF NUMBER
 Graphic representation in
which the number of
individual organism is
depicted is called pyramid
of number.
 They show the
relationship b/w
producers, herbivores &
carnivores at successive
trophic levels in terms of
their number.

5.  The number of individuals at each trophic level decreases
from the producer to the consumer level.
 Size of the organisms of this layer may be smaller than the
upper layer organism.
 The number of herbivores is less than the producers but
their size may be greater than that of producers.
 As we get to the topmost layers till the carnivores, the
number decreases & the size increases.
 There are mainly 2 reasons for the reduction in number of
individuals towards upper trophic levels
 Population growth rate at each trophic level.
 Predation upon smaller organism by larger ones.

6.  In pond ecosystem,
 The pyramid is upright. The producers which are mainly the
phytoplanktons as algae, bacteria etc are maximum in
number; the herbivores, which are smaller fish, rotifers etc
are lesser in number than the producers & the secondary
consumers, such as small fish eating each other, water
beetles etc are lesser in number than the herbivores. Finally
the top consumers, the bigger fish are least in number.
Snake,
Large fish
Small fish, frog
phytoplanktons

7.  In parasitic food chain
 The pyramids are always
inverted, this is due to the
fact that, from producers to
consumers, the number of
organisms gradually shows
an increase making the
pyramid inverted in shape.
 A tree supports a large
number of fruit eating
birds (frugivores) which in
turn supports a large
number of parasites such
as lice, bugs etc which
support many
hyperparasites.

8. PYRAMID OF BIOMASS
 Generally represent the total weight of standing crop i.e,
living matter present at each trophic level of a food chain.
 They are comparatively more fundamental, as they instead
of geometric factor, show the quantitative relationship of
standing crops.
 The pyramids are normally upright.
 In grassland & forest
 There is gradually a general decrease in biomass of
organisms at successive levels from prpducers to the top
carnivores. Thus pyramids are upright.

9.  In pond ecosystem
 As the producers are
smaller organisms, their
biomass is least & this
value gradually shows an
increase towards apex of
the pyramid, thus making
the pyramid inverted in
shape.

10. PYRAMID OF ENERGY
 Graphic representation of
amount of energy trapped
per unit time & area in
different trophic levels of
food chain.
 Clearly indicates the
reduction in the availability
of energy b/w different
trophic levels.
 The least amount of energy
produced is noticed among
secondary & tertiary
consumers.

11.  Large amount of energy is
available at the producer level
than in the successive trophic
levels.
 Maximum energy content is
present in producers, they
obtain energy from solar
radiation.
 The energy is converted into
chemical form & stored inside
organic matter manufactured
by the producers.

12.  As the energy passes into higher trophic levels along with
food, its amount decreases because of its dissipation as
heat.
 Of all 3 types of ecological pyramids, pyramid of energy
gives the best picture of overall nature of ecosystem.
 The pyramid is always erect or upright.