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Chapter 54 Ecosystems. n Ecosystem - consists of all the organisms living in a community as well as all the abiotic factors with which they interact.

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Presentation on theme: "Chapter 54 Ecosystems. n Ecosystem - consists of all the organisms living in a community as well as all the abiotic factors with which they interact."— Presentation transcript:

1 Chapter 54 Ecosystems

2 n Ecosystem - consists of all the organisms living in a community as well as all the abiotic factors with which they interact. n Trophic structure - all the feeding relationships within an ecosystem. n Trophic levels - divides the species of an ecosystem by what their main source of nutrition is.

3 Trophic Relationships in Ecosystems n Primary Producers - 1st trophic level consisting of autotrophs; the base (photosynthesize) n Primary Consumers - herbivores n Secondary Consumers - carnivores that eat herbivores n Tertiary Consumers - carnivores that eat other carnivores

4 Trophic Relationships in Ecosystems (cont) n Quarternary Consumers - high order carnivores that consume larger carnivores n Detritovores - derive energy by consuming dead organic material such as leaves, feces, and dead organisms from all trophic levels.

5 Food Chains and Food Webs n Food Chain - pathway by which food energy is passed from trophic level to trophic level –Example dandelion - grasshopper - mouse - snake - hawk (terrestrial) phytoplankton - zooplankton - small fish - medium sized fish - large fish (marine) n Food Webs - elaborate feeding relationships between all trophic levels

6 Food Chains and Food Webs (cont)

7 Ecosystem Processes n Production - rate of incorporation of energy and materials into bodies of organisms n Consumption - metabolic use for growth and reproduction of assimilated organic materials n Decomposition - breakdown of organic material into inorganic material –bacteria, fungi, and some animals –links all trophic levels recycling nutrients back into the abiotic environment

8 Energy Flow in Ecosystems n An ecosystems energy budget depends on the amount of primary productivity. –the amount of light energy converted to chemical energy (organic compounds) n Biomass - term used to describe primary productivity –the amount of new vegetation added to the ecosystem in terms of dry weight per unit time

9 Productivity of Different Ecosystems

10 Energy Flow through Ecosystems n Most of the energy is lost as it flows through each trophic level due to heat. –metabolic rate of the organism n Secondary Productivity - rate at which consumers convert chemical energy into their own new biomass. –Herbivores can only eat a fraction of the plant biomass produced, and can only digest a fraction of what they eat.

11 Energy Partitioning in a Caterpillar lost as heat converted to biomass recycled by detritovores

12 Energy Flow through Ecosystems (cont) n Ecological efficiency - percentage of energy transferred from one trophic level to the next (~10% is transferred) n Pyramid of Productivity - food chain is diagrammatically represented using blocks where the primary producers form the base n Biomass pyramid - representation of the standing crop biomass in a trophic level

13 Pyramid of Net Productivity Primary Producers only convert ~1% of light energy into biomass. Consumers convert ~10% of chemical energy into biomass.

14 Biomass Pyramid

15 Biogeochemical Cycles n Water cycle n Carbon cycle n Nitrogen cycle n Phosphorus cycle

16 Biological Magnification n Biological magnification - concentration of toxins at successive trophic levels –top-level carnivores tend to be the organisms most severely affected. n These toxins, such as DDT and PCBs, are pesticides that may accumulate in tissues after ingestion. (fat tissue)

17 Biological Magnification of DDT in a Food Chain Food Chain Concentration of DDT in A Long Island Marsh sprayed for Mosquito Control 1967 ppm Water Plankton.04 Silverside Minnow.23 Sheephead Minnow.94 Pickerel1.23 Needlefish2.07 Heron3.57 Tern3.91 Osprey13.8 Merganser22.8 Cormorant26.4

18 Human Impact-Ozone Depletion n Ozone (O 3 ) - bottom layer of the stratosphere that protects Earth from UV radiation. n Depletion since 1975 is due to CFCs, chlorflourocarbons, chemicals used in refrigerators, aerosol, and styrofoam. n Chlorine reacts with the O 3 molecules reducing them to O 2 molecules n Reactions allow the chlorine to dissociate from the O 2 molecules allowing the chlorine to react with more ozone.

19 Human Impact-Ozone Depletion (cont) Ozone is constantly produced and destroyed, however, atoms, such as Cl & Br, siphon ozone away faster than it is being produced.

20 Ozone Depletion - Antarctica


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