Chapter 57 – Dynamics of Ecosystems Trophic levels Nutrient flow
Chapter 55 Dynamics of Ecosystems
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Transcript of Chapter 55 Dynamics of Ecosystems
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.