Chapter 55 Dynamics of Ecosystems

Ecosystem

All the organisms and abiotic factors in a community.

Ecosystem Studies

1. Energy Flow – the movement of energy through trophic levels.

2. Chemical Cycling – the movement of matter from one part of the ecosystem to another.

Trophic Levels

Division of an ecosystem based on the source of nutrition (energy).

Trophic Levels

1. Primary Producers

2. Primary Consumers

3. Secondary Consumers

4. Detritivores

Primary Producers

Usually plants, capture energy and store it in chemical bonds.

Are the source of the energy available to an ecosystem.

Primary Consumers

Organisms that feed on the producers.

Ex: Herbivores

Secondary Consumers

Organisms that feed on the Primary Consumers.

Ex: Carnivores

Comment

There may be several layers of Secondary Consumers in an ecosystem.

Detritivores

Get their energy from the organic waste produced by all levels.

Ex: bacteria and fungi

Food Chain

Linear pathway of who eats who in an ecosystem.

Food Webs

Network showing all the feeding relationships in an ecosystem.

Primary Productivity

The rate at which light energy is captured by autotrophs or primary producers.

Primary Productivity

NPP = GPP - Rs NPP = Net Primary Productivity GPP = Gross Primary

Productivity Rs = Respiration

Available Energy

Daily - 1022 joules of solar radiation.

1% - captured by Ps. About 170 billion tons of

organic matter is created each year.

Primary Producers

50 - 90% of GPP is lost to Rs by the primary producers.

NPP = 10 - 50% Animals - use only NPP,

which limits the food webs.

Limiting Factors

Material or nutrient that is not present in sufficient quantity for the primary producers.

Ex: N, P, K, Mg Light, CO2

Energy Transfers

Not 100% efficient. Why? Second law of

thermodynamics. Waste. Materials that can’t be

digested etc.

Energy Transfer

Averages 10% with each Trophic Level change.

Question ?

Why do most ecosystems have only 3 - 4 trophic levels?

There isn’t enough energy passed up through the food web to support more levels.

Implications

There has to be fewer high level consumers in a food web.

The higher level consumers usually need a large geographical area.

Question

Which would support more humans per area? Eating meat? Eating plants?

Pyramids

Graphical representation of relationships in ecosystems.

Ex:1. Productivity

2. Biomass

3. Numbers

Chemical Cycling

Matter is recycled through ecosystems.

Ex: Biogeochemical Cycles

Matter Reservoirs

1. Organic Materials

2. Inorganic Materials Available Unavailable

Representative Cycles

Water Carbon Nitrogen Know one or more of these

cycles for an essay question.

Energy vs Matter

Energy - flows through ecosystems and is mostly lost as heat.

Matter - cycles in ecosystems.

Question ?

What is Man's influence on Ecosystems ?

Humans have had many negative impacts.

Hubbard Brook

Biological Magnification

The concentration of toxins in successive levels of a food web.

Ex: DDT Heavy metals

(Hg, Cd Pb)

Causes

Not broken down by digestion/decomposition.

Lipophilic. Concentrates and effects the

upper levels of the food web.

Greenhouse Effects

The trapping of heat by the Earth's atmosphere. (CO2, H2O etc.).

Carbon Dioxide Levels

Prior 1850 - 274 ppm 1958 - 316 ppm 1992 - 351 ppm

Point: the levels of CO2 are rising. The cause is probably due to humans.

Causes

Industrialization. Burning of fossil fuels. Loss of forests.

Result

Earth will heat up. Ice caps melt and sea levels

will rise. Climate shifts. Increased Ps (?)

Acid Rain

Caused by air pollution. Lowers the pH of rainfall. Is seriously damaging many

ecosystems.

Habitat Destruction

Worst problem threatening most species today.

Comment

Man has a major impact on the Biosphere.

Man needs to learn how to work with the Biosphere.

Summary

Know the tropic levels of ecosystems.

Know an example of a food chain and a food web.

Know how energy moves through an ecosystem.

Summary

Know how matter moves through an ecosystem.

Know one or more examples of matter cycling.

Be able to discuss in detail a human impact problem on ecosystems.