1. ECOSYSTEMS &
ENERGY FLOW

2. 2
Ecosystem
 A community and its physical
environment
 Made up of two essential
components:
 Abiotic factors
 Biotic factors

3. 3
Abiotic factors
 non-living components of an ecosystem
 elements which may be found in the
environment
 May be:
 Physical
 Chemical

4. 4
Physical factors
 Sunlight and shade
 Temperature and wind
 Amount of precipitation
 Altitude and latitude
 Nature of soil

5. 5
Chemical factors
 Salinity of water
 Level of dissolved O2 and other gases
 Level of plant nutrients
 pH of soil and water
 Level of natural or artificial toxic
substances

6. 6
Biotic factors
 The organisms in an ecosystem are
either:
 Autotrophs
 photoautotrophic
 chemoautotrophic
 Heterotrophs
 include humans
 animals and
 microorganisms.

7. 7
Autotrophs
 Photoautotrophs –
 has chlorophyll and carry on photosynthesis.
 Chemoautotrophs –
 bacteria that obtain energy from the oxidation
of inorganic compounds such as ammonia,
nitrites and sulfides.

8. 8
Heterotrophs
 need a source of pre-formed nutrients
 consume tissues of other organisms.
 consumers are classified according to the
type of food they eat.

9. 9
Types of Consumers
 Herbivores
 feed directly on green plants.
 Carnivores
 eat other animals.
 Omnivores
 feed on both plants and animals.

10. 10
Types of Consumers
 Decomposers
 fungi and bacteria
 extract energy from dead matter, including
waste
 return nutrients back to the soil.
 Scavengers
 feed on dead matter.

11. 11
Food Chain
 illustrates how energy and nutrients move
from one organism to another
 shows transfer of energy from one trophic
level to another

12. 12
Food Chain

13. 13
Trophic levels
 A trophic level includes a group of
organisms that obtain food in a similar
manner.
 Producers
 Primary consumers
 Secondary consumers
 Tertiary consumers
 Quaternary consumers

15. 15
Food Webs: Who Eats Whom?

16. 16
Food Web
 A complex network of interconnected
food chains
 The feeding relationship that actually
exists in nature
 May be:
 Grazing food web
 Detrital food web

18. 18
Energy Flow
 Ecosystems are dependent upon solar
energy flow and finite pools of nutrients.
 The primary source of energy for
ecosystems is sunlight.
 All energy content of organic matter is
eventually lost to the environment as
heat.

19. 19
Laws of Thermodynamics
 Energy can neither be created nor
destroyed, but can be transformed into
different forms.
 When energy is transformed from one
form to another, there is always some loss
of energy from the system, usually as low
grade heat.

20. 20
10% Law of Energy Transfer
 only 10% of energy at a particular trophic
level is incorporated into the next trophic
level.
 rapid loss of energy explains why a food
chain rarely has five links.

22. 22
Energy Flow

23. 23
Ecological Pyramids
 Graphic representations of the relative
energy amounts at each trophic level.
 3 Types of Pyramids
1. Pyramid of Energy
2. Pyramid of Biomass
3. Pyramid of Numbers

24. 24
Pyramid of Energy
 Energy content of each trophic level
 Unit of energy = Kilocalories/meter2
/year
 Pyramid has large base and gets significantly
smaller at each level.
 Organisms use energy for work and respiration,
so less energy is available to each successive
trophic level.

25. 25
Pyramid of Energy
 energy at each
trophic level
expressed in
kcal/m2/yr.

26. 26
Pyramid of Biomass
 Biomass is a quantitative estimate of the total
mass (amount) of living material…or
…the amount of fixed energy at a given time.
 Measuring biomass: total volume, dry weight, or
live weight
 A 90% reduction occurs between each trophic
level

27. 27
Pyramid of Biomass
 Biomass also
diminishes with the
distance along the
food chain from the
autotrophs which
make the organic
molecules in the first
place.

28. 28
Pyramid of Numbers
 Illustrates number of organisms at each
trophic level
 more individuals at the lower trophic
levels.
 BUT some number pyramids can be
inverted.

29. 29
Pyramid of Numbers
 Small animals are
more numerous than
larger ones.
 If the size of the
individuals at a given
trophic level is small,
their numbers can be
large and vice versa.

30. 30
Identify the food chains and write the trophic level for each
organism in this food web.

31. Food Web Activity: