Ecology & Environmemnt

1. Energy Flow in EcosystemsEnergy Flow in Ecosystems
Course Teacher
Dr. Muhammad Azizul Hoque

2. Introduction
 Energy is the capacity to do work; Potential energy is
the energy at rest & Kinetic energy is due to motion
 Two laws of thermodynamics are very important to
understand energy flow in ecosystems
- 1st law (law of conservation of energy): energy is neither
created nor destroyed
- 2nd law: whenever energy is transformed from one kind to
another, there is an increase in entropy and decrease in the
amount of useful energy

3. Energy produced from the reaction / used in the reaction
Wood
Burn
Heat Energy
Disordered
molecule
Exothermic
reaction
Measure of
relative
disorder is
known as
EntropyEndothermic reaction (Photosynthesis as an example):
6CO2 + 6H2O + Sunlight 6C6H12O6 + 6O2
CO2 from
atm
Water from
soil
Sugar in plant
cell
Oxygen released
to atm

4. Energy in an Ecosystem
Photosynthetic Autotrophs:
6CO2 + 6H2O + Sunlight C6H12O6 + 6O2
CO2 from
atm
Water from
soil
Sugar in plant
cell
Oxygen released
to atm
 Living organisms can use energy in several form, but all can be grouped
under one of two headlines: radiant and fixed
- Radiant energy: .. in the form electromagnetic waves such as light
- Fixed energy: potential chemical energy bounded up in various organic
substances
 Conversion of radiant energy to fixed energy can be explained by
Photosynthesis Process
C6H12O6 + 6O2 6CO2 + 6H2O + Usable energy
Respiration:

5. Destination of Carbohydrate

6. Pattern of flow of Energy through the Ecosystems
 Need to be familiar with the terms Food chain & Trophic level
 Food Chain: Living organisms in an ecosystem are interdependent
for their food. The patterns of eating and being eaten forms a linear
chain called Food chain in the ecosystem which can always be
traced back to the producers. Two types of food chains: grazing
food chain & detritus food chain
 Trophic level: It is the number of links by which the position of
organisms is separated from the producer, or as the nth position in
the food chain.

7. Pattern of flow of Energy through the Ecosystems

8. Energy in an Ecosystem• Food Chain that starts from greed plants and ends to
carnivors by passing through herbivors is called Grazing
Food Chain.

9. Energy in an Ecosystem
• The term ‘Detritus’ represents the organic wastes, exudates
and dead matter derived from the grazing food chain.
• It serves as the source of energy for a group of organisms
(detritivors) and are separated from grazing food chain.

10. Ecological Pyramids
 Definition
 Types of Ecological Pyramids
 Short notes on each types with sketch