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:
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. 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.
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
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.
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
Food Chains and Food Webs (cont)
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
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
Productivity of Different Ecosystems
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.
Energy Partitioning in a Caterpillar lost as heat converted to biomass recycled by detritovores
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
Pyramid of Net Productivity Primary Producers only convert ~1% of light energy into biomass. Consumers convert ~10% of chemical energy into biomass.
Biogeochemical Cycles n Water cycle n Carbon cycle n Nitrogen cycle n Phosphorus cycle
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)
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
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.
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.