1. Lecture #2 How Ecosystems Work

2. Biosphere Breakdown

3. Organism-any form of life (1 individual)
Species- all organisms of the same kind that are genetically similar enough to breed in nature and produce live, fertile offspring
Population-individuals of the same species in an area
Biological Community-populations of different species living
& interacting in a given area

4. Ecosystem-many interacting communities in a specific place including abiotic factors Biome- large terrestrial regions characterized by a distinct climate & specific life–forms, especially vegetation, adapted to the region Ecosphere-(=biosphere)-all of Earth’s biomes together

5. What drives an ecosystem?
Photosynthesis is at the base of all ecosystems so photosynthesizers (usually plants) are called the producers.
Productivity - the amount of biomass produced in a given area in a given period of time. Photosynthesis is called primary productivity because it is basic to all other growth in an ecosystem.
Secondary productivity - manufacture of biomass by organisms that eat plants

6. From Species to Ecosystems
Ecosystem - biological community (biotic factors) and its physical environment (abiotic factors)
The elements are interacting to process energy and cycle materials
Most ecosystems are open in that they exchange materials and organisms with other ecosystems.
It is difficult to define the boundaries of an ecosystem.

7. Major Components of Ecosystems
Major components of aquatic ecosystems.
© Brooks/Cole Publishing Company / ITP

8. Food Chains and Food Webs
Food Chain - A sequence that shows the manner in which energy is transferred from one organism to another , as each organism eats another, in an ecosystem.

9. Food web –a complex of interconnected food chains in an ecosystem.
These show the many feeding relationships in an ecosystem.
In an ecosystem of average complexity, numerous pathways are possible.  
Food webs are a more realistic model of the flow of energy and materials through an ecosystem.

12. Trophic pyramids
Food Chains can also be represented by an ecological pyramid by arranging the organisms at various trophic levels diagrammatically.
Notice that there are many more producers than consumers.
Each trophic level consists of organisms that get their energy in the same way.

14. Which organisms make up each trophic level?
Plants (producers) make up the first trophic level.
Animals are consumers.
2nd trophic level: Primary Consumers:- Animals that eat plants.
3rd trophic level: Secondary Consumers- Animals that eat primary consumers
4th trophic level: Tertiary consumers- Animals that eat secondary consumers
* Organisms may occupy more than one trophic level!

15. Organisms can also be identified by the type of food they consume:
What they eat Examples
Herbivores (Plants) {Deer}
Carnivores (Meat) {Wolves}
Omnivores (Plants/Meat) {Bears}
Scavengers (Carcasses) {Crows}
Detritivores (Debris) {Ants}
Decomposers (All) {Bacteria}

16. Ecological Pyramids & Energy Transfer
Due to the Second Law of Thermodynamics, energy is lost at each level of the pyramid.
10% Rule (Energy / Biomass) - as an organism is consumed, about 90% of the energy at each trophic level is lost or used up along the way (as heat in metabolic processes).
Only about 10% of the energy becomes part of the consumers body.
This 10% is all that is available to the next trophic level when one organism consumes another.

17. Examples
1 kg fox
10 kg rabbit
100 kg clover