Chapter 54: Ecosystems

Ecosystem All the organisms and abiotic factors in a

community.

Ecosystem Studies1. 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).

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.

Consumers 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. 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. 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.

Greenhouse Effects Causes

Industrialization. Burning of fossil fuels. Loss of forests.

Results 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.

Exotic Species When transplanted species are too successful

and upset the ecosystem in new areas. Ex: Starlings

Fire Ants Carp

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.