3. Ecosystem- Functioning, Biogeochemical Cycles

8/2/2019 3. Ecosystem- Functioning, Biogeochemical Cycles

1/22

- Structure and Function II


2/22

TROPHIC STRUCTURE

e pro ucers an consumers are arrange n t e ecosystem n a

definite manner and their interaction along with population size are expressed

together as trophic structure

The flow of ener is mediated throu h a series of feedin

relationships in a definite sequence or pattern which is known as food chain.

Nutrients and energy too move along the food chain.

Trophic Level/Feeding level

Each food level is known as trophic level and the amount of living

ma er a eac rop c eve a a g ven me s nown as s an ng crop or

standing biomass.


3/22

FOOD CHAINS

food chain.

ii. All organisms, living or dead, are otential food for some other organism

and thus, there is essentially no waste in the functioning of a natural

ecosystem.

iii. Each organism in the ecosystem is assigned a feeding level or

trophic level depending on its nutritional status.


4/22


5/22


6/22

II. Detritus food chain

Starts with dead organic matter

Detritivores and decomposers follow the order

Even the detritivores are consumed by decomposers


7/22

Food chains in ecosystems are rarely found to o erate as isolated

linear sequences.

Usually interconnected and form a complex network with several

linkages and are known as food webs.

Definition:

Food web is a network of food chains where different types of

organisms are connected at different trophic levels, so that there are a

number of options of eating and being eaten at each trophic level.


8/22


9/22

a. Energy flow and nutrient cycling

b. Maintenance and re ulation of o ulation

size of different animals

c. Maintenance of ecological balance

d. Biological magnification


10/22

ECOLOGICAL PYRAMIDS

Graphic representation of trophic structure and function of an

ecosystem, starting with producers at the base and successive trophic

.

Ecological pyramids are of three types:

A. Pyramid of numbers

.

C. Pyramid of Energy


11/22

Pyramid of numbers

It represents the number of individual organisms at each trophic level

Upright or inverted pyramid , depending upon the type of ecosystem

Fig: Grass land ecosystem Fig: Forest ecosystem


12/22

Pyramid of biomass Represents the total biomass (dry matter) at each trophic level in a food chain

,

Forest Ecosystem Pond Ecosystem


13/22

Pyramid of Energy

Represents the amount of energy present at each trophic

Always upright

At ever successive tro hic level there is a hu e loss of ener about 90%

Energy loss in the form of heat, respiration etc.


14/22

ENERGY FLOW IN AN ECOSYSTEM

The energy flow is always unidirectional

The flow of energy follows the two laws of Thermodynamics:

energy can neither be created nor be destroyed but it can be

transformed from one form to another.

energy dissipates as it is used or in other words, its gets converted

from a more concentrated to dispersed form.

As energy flows through the food chain, energy dissipates at every

trophic level

The loss of energy takes place through respiration, loss of energy in

locomotion, running, hunting and other activities.

t every eve t ere s a out oss o energy an t e energy

transferred from one trophic level to the other is only about 10%.


15/22

Productivity of Ecosystem

Primary productivity : The rate at which radiant energy is converted into

-

producers.

i Gross rimar roductivit

It refers to the total rate of photosynthesis including the organic matter used

up in respiration, i.e., amount of CO2 fixed/g chl/hour.

(ii) Net primary productivity NPP = GPP R

It is the rate of storage of organic matter in plant tissues in excess

of the respiratory utilization by plants.

SECONDARY PRODUCTION

The amount of organic matter stored by the herbivores or carnivores (in excess of

respiratory loss) is known as secondary production.


16/22

CYCLES


17/22

Water Cycle


18/22

Oxygen Cycle


19/22

Nitrogen cycle


20/22

Carbon Cycle


21/22

Phosphorus cycle


22/22

Sulphur cycle

3. Ecosystem- Functioning, Biogeochemical Cycles

Documents

Transcript of 3. Ecosystem- Functioning, Biogeochemical Cycles