BIOLOGY CONCEPTS & CONNECTIONS Fourth Edition Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Neil A. Campbell Jane B. Reece Lawrence G. Mitchell Martha R. Taylor From PowerPoint ® Lectures for Biology: Concepts & Connections CHAPTER 36 Communities and Ecosystems Modules – 36.20

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Biomass is the amount of living organic material in an ecosystem Primary production is the rate at which producers convert sunlight to chemical energy –The primary production of the entire biosphere is about 170 billion tons of biomass per year Energy supply limits the length of food chains

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A pyramid of production reveals the flow of energy from producers to primary consumers and to higher trophic levels Figure Tertiary consumers Secondary consumers Primary consumers Producers 10 kcal 100 kcal 1,000 kcal 10,000 kcal 1,000,000 kcal of sunlight

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Only about 10% of the energy in food is stored at each trophic level and available to the next level –This stepwise energy loss limits most food chains to levels –There is simply not enough energy at the very top of an ecological pyramid to support another trophic level

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The dynamics of energy flow apply to the human population as much as to other organisms –When we eat grain or fruit, we are primary consumers –When we eat beef or other meat from herbivores, we are secondary consumers –When we eat fish like trout or salmon (which eat insects and other small animals), we are tertiary or quaternary consumers Connection: A production pyramid explains why meat is a luxury for humans

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Because the production pyramid tapers so sharply, a field of corn or other plant crops can support many more vegetarians than meat- eaters Figure Secondary consumers Primary consumers Producers Human vegetarians Corn Human meat-eaters Cattle Corn TROPHIC LEVEL

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Ecosystems require daily infusions of energy –The sun supplies the Earth with energy –But there are no extraterrestrial sources of water or other chemical nutrients Nutrients must be recycled between organisms and abiotic reservoirs –Abiotic reservoirs are parts of the ecosystem where a chemical accumulates Chemicals are recycled between organic matter and abiotic reservoirs

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings There are four main abiotic reservoirs –Water cycle –Carbon cycle –Nitrogen cycle –Phosphorus cycle

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Heat from the sun drives the global water cycle –Precipitation –Evaporation –Transpiration Water moves through the biosphere in a global cycle

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure Solar heat Precipitation over the sea (283) Net movement of water vapor by wind (36) Flow of water from land to sea (36) Water vapor over the sea Oceans Evaporation from the sea (319) Evaporation and transpiration (59) Water vapor over the land Precipitation over the land (95) Surface water and groundwater

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Carbon is taken from the atmosphere by photosynthesis –It is used to make organic molecules –It is returned to the atmosphere by cellular respiration The carbon cycle depends on photosynthesis and respiration

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure CO 2 in atmosphere Cellular respiration Higher-level consumers Primary consumers Plants, algae, cyanobacteria Photosynthesis Wood and fossil fuels Detritivores (soil microbes and others) Detritus Decomposition Burning

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Nitrogen is plentiful in the atmosphere as N 2 –But plants cannot use N 2 Various bacteria in soil (and legume root nodules) convert N 2 to nitrogen compounds that plants can use –Ammonium (NH 4 + ) and nitrate (NO 3 – ) The nitrogen cycle relies heavily on bacteria

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Some bacteria break down organic matter and recycle nitrogen as ammonium or nitrate to plants Other bacteria return N 2 to the atmosphere

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure Nitrogen (N 2 ) in atmosphere Amino acids and proteins in plants and animals Assimilation by plants Denitrifying bacteria Nitrates (NO 3 – ) Nitrifying bacteria Detritus Detritivores Decomposition Ammonium (NH 4 + ) Nitrogen fixation Nitrogen-fixing bacteria in soil Nitrogen-fixing bacteria in root nodules of legumes Nitrogen fixation

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Phosphates (compounds containing PO 4 3- ) and other minerals are added to the soil by the gradual weathering of rock Consumers obtain phosphorus in organic form from plants Phosphates are returned to the soil through excretion by animals and the actions of decomposers The phosphorus cycle depends on the weathering of rock

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure Uplifting of rock Phosphates in solution Weathering of rock Phosphates in rock Phosphates in organic compounds Detritus Detritivores in soil Phosphates in soil (inorganic) RockPrecipitated (solid) phosphates Plants Animals Decomposition Runoff

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Experimental studies have been performed to determine chemical cycling in ecosystems A study to monitor nutrient dynamics has been ongoing in the Hubbard Brook Experimental Forest since Connection: Ecosystem alteration can upset chemical cycling ECOSYSTEM ALTERATION

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Dams were built across streams at the bottom of each watershed to monitor water and nutrient losses Figure 36.18A

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings In 1966, one of the valleys was completely logged –It was then sprayed with herbicides for 3 years to prevent plant regrowth –All the original plant material was left in place to decompose Figure 36.18B

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Researchers found that the total removal of vegetation can increase the runoff of water and loss of soil nutrients Figure 36.18C

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Environmental changes caused by humans can unbalance nutrient cycling over the long term –Example: acid rain

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Eutrophication is a process in which nutrient runoff from agricultural lands or livestock operations causes photosynthetic organisms in ponds and lakes to multiply rapidly –The result is algal bloom Talking About Science: David Schindler talks about the effects of nutrients on freshwater ecosystems

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Algal bloom can cause a pond or lake to lose much of its species diversity –Human-caused eutrophication wiped out fisheries in Lake Erie in the 1950s and 1960s Figure 36.19B

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Dr. David Schindler is an ecologist who worked at the Experimental Lakes Project in northern Ontario –He performed several classic experiments on eutrophication that led to the ban on phosphates in detergents Figure 36.19A

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings According to Dr. Schindler, there are three serious threats to freshwater ecosystems –Acid precipitation –Climate warming –Changes in land use

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The human alteration of ecosystems threatens the existence of thousands of species To slow the disruption of ecosystems, some nations are establishing zoned reserves –These are undisturbed wildlands surrounded by buffer zones of compatible economic development Connection: Zoned reserves are an attempt to reverse ecosystem disruption

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Costa Rica has established eight zone reserves Costa Rica looks to its zoned reserve system to maintain at least 80% of its native species

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings –On this map, the reserves are shown in green and the buffer zones in yellow Figure Guanacaste Arenal Bajo Tempisque Cordillera Volcanica Central Pacifico Central Peninsula de Osa NICARAGUA COSTA RICA Caribbean Sea Llanuras de Tortuguero La Amistad PANAMA Pacific Ocean