Chapter 54: 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). 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 joules of solar radiation.  1% - captured by Ps.  About 170 billion tons of organic matter is created each year.

Primary Producers  % of GPP is lost to Rs by the primary producers.  NPP = %  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, CO 2

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 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. (CO 2, H 2 O etc.).  Carbon Dioxide Levels Prior ppm ppm ppm  Point: the levels of CO 2 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.