ECOSYSTEMS. Follow along in chapter 54. *Means less important

Transcription

1 ECOSYSTEMS Follow along in chapter 54 *Means less important

2 How do ecosystems function? What is an ecosystem? All living things in an area and their abiotic environment Ecosystem function can be easily summed up Matter moves in cycles Energy flows through the system

3 Ecosystems and Physical Laws The laws of physics and chemistry apply to ecosystems Particularly in regard to the flow of energy Energy is conserved But degraded to heat during ecosystem processes

4 Trophic Relationships Energy and nutrients pass from primary producers (autotrophs) To primary consumers (herbivores) and then to secondary consumers (carnivores)

5 Energy flows through an ecosystem Entering as light and exiting as heat Tertiary consumers Microorganisms and other detritivores Secondary consumers Detritus Primary consumers Primary producers Key Heat Chemical cycling Energy flow Sun Figure 54.2

6 Nutrients cycle within an ecosystem Water Carbon Nitrogen Phosphorous

7 *Decomposition Decomposition Connects all trophic levels Materials broken down and recycled

8 Ecosystem primary production What is primary production in an ecosystem? The amount of light energy converted to chemical energy by autotrophs The extent of photosynthetic production sets the limit for the energy budget of the entire ecosystem Basically plants are the primary source for all the energy that exists in an ecosystem They got the energy from the sun and no other organism is doing that

9 Gross and Net Primary Production Total primary production in an ecosystem is known as that ecosystem s gross primary production (GPP) Not all of this production is stored as organic material (carbohydrates) in the growing plants Why not? They use some of this energy themselves for growth Net primary production (NPP) Is equal to GPP minus the energy used by the primary producers for respiration Only NPP is available to consumers Why is this important? There has to be enough NPP to support all the other species in an ecosystem

10 *Different ecosystems vary considerably in their net primary production And in their contribution to the total NPP on Earth Open ocean Continental shelf Estuary Algal beds and reefs Upwelling zones Extreme desert, rock, sand, ice Desert and semidesert scrub Tropical rain forest Savanna Cultivated land Boreal forest (taiga) Temperate grassland Woodland and shrubland Tundra Tropical seasonal forest Temperate deciduous forest Temperate evergreen forest Swamp and marsh Lake and stream ,500 2, ,200 1,300 1,600 2,200 2, Key Marine Terrestrial Freshwater (on continents) ,000 1,500 2,000 2, (a) Percentage of Earth s surface area (b) Average net primary production (g/m 2 /yr) Figure 54.4a c (c) Percentage of Earth s net primary production

11 *A limiting nutrient is the element that must be added in order for production to increase Nitrogen and phosphorous are common limiting nutrients The addition of large amounts of nutrients to lakes has a wide range of ecological impacts Sewage and fertilizer run off leads to eutrophication Excessive plant growth of plant life-can lead to fish species loss Figure 54.7

12 Major big idea of this awesome powerpoint: Energy transfer between trophic levels is usually less than 20% efficient A good average estimate is 10% The secondary production of an ecosystem is the amount of chemical energy in a consumers food that is converted to their own new biomass Basically if that energy is used by an organism to build up their biomass, then they have stored all that energy in themselves

13 Major big idea of this awesome powerpoint: Energy transfer between trophic levels is usually less than 20% efficient A good average estimate is 10% The secondary production of an ecosystem is the amount of chemical energy in consumers food that is converted to their own new biomass during a given period of time

14 Production Efficiency When a caterpillar feeds on a plant leaf only about one-sixth of the energy in the leaf is used for secondary production That s not very much. Where does the rest of the energy go? Check out the picture Plant material eaten by caterpillar 200 J So, what happens to all that stored energy when the caterpillar gets eaten? Feces 100 J 33 J Growth (new biomass) 67 J Cellular respiration

15 Trophic Efficiency and Ecological Pyramids It gets transferred to the organism that ate the caterpillar Trophic efficiency Plant material eaten by caterpillar Percentage of production transferred from one trophic level to the next 200 J Usually ranges from 5% to 20% Feces 100 J 33 J 67 J Cellular respiration Growth (new biomass)

16 Trophic Efficiency and Ecological Pyramids Trophic efficiency is really low because lots of energy gets used and lost every time something eats something else Plants start will 100% of captured energy Caterpillar gets 20% or less from the plant Bird gets 20% or less from the caterpillar (4% of original) Snake gets 20% or less from the bird (0.8% of original) Feces 100 J Plant material eaten by caterpillar 200 J 33 J Growth (new biomass) 67 J Cellular respiration

17 Pyramids of Production This loss of energy with each transfer in a food chain can be represented by a pyramid of net production The higher the trophic level, the less energy available Tertiary consumers 10 J Secondary consumers 100 J Primary consumers 1,000 J Primary producers 10,000 J Figure ,000,000 J of sunlight

18 Pyramids of Biomass How does less energy at higher trophic levels affect an ecosystem? Because there is less energy as you go up, there are fewer individuals in each higher trophic level Fewer individuals = less matter A biomass pyramid shows this relationship Amount of matter found in an individual or group of individuals Trophic level Tertiary consumers Secondary consumers Primary consumers Primary producers Dry weight (g/m 2 ) (a) Most biomass pyramids show a sharp decrease in biomass at successively higher trophic levels, as illustrated by data from a bog at Silver Springs, Florida.

19 *Some aquatic ecosystems have inverted biomass pyramids Trophic level Dry weight (g/m 2 ) Primary consumers (zooplankton) Primary producers (phytoplankton) 21 4 (b) In some aquatic ecosystems, such as the English Channel, a small standing crop of primary producers (phytoplankton) supports a larger standing crop of primary consumers (zooplankton). Figire 54.12b

20 Pyramids of Numbers A pyramid of numbers represents the number of individual organisms in each trophic level Trophic level Tertiary consumers Secondary consumers Primary consumers Primary producers Number of individual organisms 3 354, ,624 5,842,424 Figure 54.13

21 The dynamics of energy flow through ecosystems have important implications for the human population Eating meat is a relatively inefficient way of tapping photosynthetic production Eating consumers = less available energy Worldwide agriculture could successfully feed many more people if humans all fed more efficiently, eating only plant material Trophic level Secondary consumers Primary consumers Primary producers

22 Matter moves from organic to inorganic and back again Nutrients move between organic and inorganic parts of the ecosystem Life depends on the recycling of essential chemical elements Nutrient circuits that cycle matter through an ecosystem involve both biotic and abioticcomponents and are often called biogeochemical cycles

23 A General Model of Chemical Cycling All elements cycle between organic and inorganic reservoirs Elements exist as gaseous forms in the atmosphere and cycle globally carbon, oxygen, sulfur, and nitrogen Less mobile elements cycle more in a local level phosphorous, potassium, and calcium

24 Biogeochemical Cycles The water cycle and the carbon cycle THE WATER CYCLE THE CARBON CYCLE Solar energy Net movement of water vapor by wind Transport over land CO 2 in atmosphere Cellular respiration Photosynthesis Precipitation over ocean Evaporation from ocean Evapotranspiration from land Precipitation over land Burning of fossil fuels and wood Higher-level Primary consumers consumers Runoff and groundwater Percolation through soil Carbon compounds in water Detritus Decomposition Figure 54.17

25 Water moves in a global cycle Driven by solar energy The carbon cycle works based on the reciprocal processes of photosynthesis and cellular respiration

26 The nitrogen cycle and the phosphorous cycle THE NITROGEN CYCLE THE PHOSPHORUS CYCLE N 2 in atmosphere Rain Assimilation Geologic uplift Weathering of rocks Runoff Plants Nitrogen-fixing bacteria in root nodules of legumes Ammonification Decomposers Nitrification NO 3 Denitrifying bacteria Nitrifying bacteria Sedimentation Leaching Soil Plant uptake of PO 4 3 Consumption NH 3 NH 4 + NO 2 Nitrogen-fixing soil bacteria Nitrifying bacteria Decomposition Figure 54.17

27 Most of the nitrogen cycling in natural ecosystems involves local cycles between organisms and soil or water The phosphorus cycle is relatively localized

28 Decomposition and Nutrient Cycling Rates Decomposers (detritivores) play a key role in the general pattern of chemical cycling The rates at which nutrients cycle in different ecosystems are extremely variable, mostly due to differences in rates of decomposition Consumers Producers Nutrients available to producers Abiotic reservoir Decomposers Figure Geologic processes

29 Humans can mess up ecosystems Check out 55.1 in your book and see some specific ways that people make ecosystems unstable Just read the headings