1. Energy flow in ecosystems

2. What is an ecosystem?
System = regularly interacting and interdependent components forming a unified whole
Ecosystem = an ecological system; = a community and its physical environment treated together as a functional system.

3. OR, MORE SIMPLY
an ecosystem is composed of the organisms and physical environment of a specified area.
SIZE: micro to MACRO

4. THE RULES OF ECOLOGY F. A. BAZZAZ:
1. Everything is connected to everything else.
2. Everything must go somewhere.
3. There is no such thing as a free lunch

5. To understand any system you must understand the next larger system.
H. T. Odum:
To understand any system you must understand the next larger system.

6. Attributes of Ecosystems
Order
Development
Metabolism (energy flow)
Material cycles
Response to the environment
Porous boundaries
Emphasis on function, not species

7. ENERGY FLOW IN ECOSYSTEMS
All organisms require energy, for growth, maintenance, reproduction, locomotion, etc.
Hence, for all organisms there must be: A source of energy
A loss of usable energy

8. Types of energy mechanical energy (+gravitational energy, etc.)
heat energy
mechanical energy (+gravitational energy, etc.)
chemical energy = energy stored in
molecular bonds

9. Transformations of energy
How is solar energy converted to chemical energy?
How does this process influence life as we see it on earth?
The transformations of energy from solar radiation to chemical energy and mechanical energy and finally back to heat are a traditional topic of Ecosystem Ecology.

10. An ecosystem has abiotic and biotic components:
ABIOTIC components: Solar energy provides practically all the energy for ecosystems. Inorganic substances, e.g., sulfur, boron, tend to cycle through ecosystems. Organic compounds, such as proteins, carbohydrates, lipids, and other complex molecules, form a link between biotic and abiotic components of the system.

11. BIOTIC components:
The biotic components of an ecosystem can be classified according to their mode of energy acquisition.
In this type of classification, there are:
Autotrophs
and
Heterotrophs

12. Autotrophs Autotrophs (=self-nourishing) are called primary producers.
Photoautotrophs fix energy from the sun and store it in complex organic compounds
(= green plants, algae, some bacteria)

13. photoautotroph's light simple inorganic compounds complex organic

14. Chemoautotrophs (chemosynthesizers) are bacteria
that oxidize reduced inorganic substances
(typically sulfur and ammonia compounds)
and produce complex organic compounds.

15. chemoautotrophs oxygen reduced inorganic compounds complex organic

16. Chemosynthesis near hydrothermal vents

17. Other chemoautotrophs:
Nitrifying bacteria in the soil under our feet!

18. Heterotrophs
Heterotrophs (=other-nourishing) cannot produce their own food directly from sunlight+ inorganic compounds. They require energy previously stored in complex molecules.

19. heterotrophs heat complex organic compounds simple inorganic compounds
(this may include several steps, with
several different types of organisms)

20. Heterotrophs can be grouped as:
consumers
decomposers

21. Consumers feed on organisms or particulate organic matter.
Decomposers utilize complex compounds in dead protoplasm.
Bacteria and fungi are the main groups of decomposers.
Bacteria are the main feeders on animal material.
Fungi feed primarily on plants, although bacteria also are important in some plant decomposition processes.

22. The Laws of Thermodynamics
Energy flow is a one-directional process.
sun---> heat (longer wavelengths)
FIRST LAW of THERMODYNAMICS:
Energy can be converted from one form to another, but cannot be created or destroyed.

23. Energy flow through biological systems

24. Food Chains
Food Chain: series of events in which one organism eats another and obtains energy

25. Food Chains Continued
Arrows always points in the direction of energy flow
1st organism is always the producer
2nd organism is the consumer that eats the producer
Primary consumer
3rd organism is the consumer that eats the 1st level consumer
Secondary consumer
And so on…..

26. Each organism in food chain represents a “feeding” or TROPHIC LEVEL
3rd Trophic
Level
2o or 3o consumer
2nd Trophic
Level
1o or 2o consumer
1st Trophic Level
producers
decomposers

28. SECOND LAW of THERMODYNAMICS

29. Energy Transfer
Only about 10% of energy is transferred from one level to the next
The other 90% is used by the organism to carry out its life processes or it is lost to the environment

30. 2nd Law of Thermodynamics: energy is not transferred from one object/organism to the next with 100% efficiency
Some of the energy is lost to the environment
Energy Pyramid shows the amounts of energy that moves from one level to the next

31. 2nd Law states that energy goes from a concentrated form into a dispersed form
i.e. the availability of energy to do work therefore diminishes
and the system becomes increasingly disordered.

32. Examples
Internal combustion engines in cars are 25% efficient in converting chemical energy to kinetic energy; the rest is not used or is lost as heat.
My house, particularly my girls' rooms, goes from a complex, ordered state to a simpler, disordered state.

33. So what is needed to create order?
ENERGY
As less energy becomes available ,disorder
( ENTROPHY) increases.

34. Entropy of ISOLATED SYSTEM?
ENTROPY tends to INCREASE spontaneously.

35. UNIVERSE AN ISOLATED SYSTEM
Entropy increasing
In billions of years’ time
No more energy will be present.

36. ARE NATURAL SYSTEMS AN ISOLATED SYSTEMS?
Must always be an input of energy for work
to replace that lost through the inefficient transfer of energy.
MATTER can be RECYCLED, ENERGY cannot be made available again.

37. Energy flow Simplistically: heat Producers Consumers Decomposers heat
This pattern of energy flow among different organisms is the TROPHIC STRUCTURE of an ecosystem.
heat
Producers
Consumers
Decomposers
heat

38. Terminology of trophic levels
We can further separate the TROPHIC LEVELS, particularly the Consumers:
Producers (Plants, algae, cyanobacteria; some chemotrophs)--capture energy, produce complex organic compounds
Primary consumers--feed on producers
Secondary consumers--feed on primary consumers
Tertiary consumers--feed on secondary consumers

39. More trophic levels:
Detritivores--invertebrates that feed on organic wastes and dead organisms (detritus) from all trophic levels
Decomposers--bacteria and fungi that break down dead material into inorganic materials

40. Carnivores Carnivores can be further divided into groups:
quaternary carnivore (top)
tertiary carnivore
secondary carnivore
primary carnivore
The last carnivore in a chain, which is not usually eaten by any other carnivore, is often referred to as the top carnivore.

41. Problems
Too simplistic
No detritivores
Chains too long

42. Rarely are things as simple as grass, rabbit, hawk, or indeed any simple linear sequence of organisms. More typically, there are multiple interactions, so that we end up with a FOOD WEB.