Part Two: Dynamics of Ecosystems

Lesson #2Energy Flow in an Ecosystem

Food Chain

Trophic Level

• a diagram illustrating the feeding relationships between specificproducers and consumers

• these diagrams show the sequence of organisms through which energy is passed

• refers to each step (level) in a food chain

Food Web

Top Carnivore

• a diagram that shows the relationship between a number of food chains

• this more complex diagram is needed because typically animals feed on more than one type of organism

• the arrows indicate the direction that the energy “flows” through the ecosystem

Note: It is sometimes possible for an organism to occupy more than one trophic level

• This term is given to a consumer that is not eaten by anything in the food web

• Often considered the “top of the food chain”

What are some Producers?

Primary Consumers?

Secondary Consumers?

Tertiary Consumers?

Top Carnivore?

Ecological Pyramids

• These diagrams are used to provide general information about the energy flow and stability of an ecosystem

• These diagrams show the relationships between Trophic Levels BUT NOT Feeding Relationships

• There are THREE Types:1. Pyramid of Numbers2. Pyramid of Biomass3. Pyramid of Energy

1.Pyramid of Numbers

• Usefulness:- provides general population information

• Limitations

- doesn’t show feeding relationsips- Often leads to misleading conclusions

• this diagram shows the number of organismsin one trophic level required to support a certain number of organisms at a successively higher trophic level

2.Pyramid of Biomass

• Usefulness:

provides information about trophic level size and diversity

• Limitations

Does not provide information about feeding relationships.

Not all Biomass can be consumed

• This diagram shows the total amount of living material (biomass) available at each trophic level.

• this diagram also shows the amount of biomass (food) available to higher trophic levels. In theory 100% of the biomass at one trophic level is available to a higher trophic level

3. Pyramid of Energy

• This diagram is used to describe the energy flow among the trophic levels of an ecosystem

• The area at the bottom of the pyramid represents the greatest amount of energy in an ecosystem

• As energy passes from producers to consumers, less energy is available at each successive trophic level

• Only about 10% of the energy taken in by one trophic level is passed up to the next level

3. Pyramid of Energy

• Usefulness:

most useful in determining the stability of an ecosystem

Energy = Stability

• Limitations

does not provide info about feeding relationships

What is Symbiosis?

Symbiosis is an evolved interaction or close living relationship between organisms from different species. In these relationships energy can be transferred without one organism consuming the other.

3 common types of Symbiotic Relationships:

1.Mutualism

2.Commensalism

3.Parasitism

• In this relationship both organisms benefit from their association.

(ex. Termites have micro-organisms living in their digestive tracts to help them break down cellulose. In return the termites body provides the micro-organisms a place to live and food)

• In this relationship, one organism benefits from the relationship while the other is not affected.

(ex. Pilotfish live within the body of sharks. The pilotfisheat the scraps left over from the shark’s feeding. However, the pilotfish do not help or hurt the shark.)

• In this relationship, one organism (the parasite) benefits while the other organism (the host) is harmed or killed

(ex. Tapeworms attach to the intestines of host organisms and absorb the digested nutrients of the host harming the host)