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 36.5 – 36.10

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A symbiotic relationship is an interaction between two or more species that live together in direct contact There are three main types of symbiotic relationships within communities –Parasitism –Commensalism –Mutualism 36.5 Symbiotic relationships help structure communities

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Parasitism is a kind of predator-prey relationship –The parasite benefits and the host is harmed in this symbiotic relationship –A parasite obtains food at the expense of its host –Parasites are typically smaller than their hosts

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings In the 1940s, Australia was overrun by hundreds of millions of European rabbits –The rabbits destroyed huge expanses of Australia –They threatened the sheep and cattle industries In 1950, a parasite that infects rabbits (myxoma virus) was deliberately introduced to control the rabbit population Figure 36.5A

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Commensalism is a symbiotic relationship where one partner benefits and the other is unaffected Examples of commensalism –Algae that grow on the shells of sea turtles –Barnacles that attach to whales –Birds that feed on insects flushed out of the grass by grazing cattle

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Mutualism is a symbiotic relationship where both partners benefit Examples of mutualism –Nitrogen-fixing bacteria and legumes –Acacia trees and the ants of the genus Pseudomyrmex Figure 36.5B

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Disturbances include events such as storms, fires, floods, droughts, overgrazing, and human activities –They damage biological communities –They remove organisms from communities –They alter the availability of resources 36.6 Disturbance is a prominent feature of most communities Figure 36.6

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Ecological succession is a transition in the species composition of a community following a disturbance –Primary succession is the gradual colonization of barren rocks by living organisms –Secondary succession occurs after a disturbance has removed the vegetation but left the soil intact

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Ecologist Frank Gilliam is especially interested in the role that fire plays in shaping ecosystems –According to Dr. Gilliam, fire is a key abiotic factor in many ecosystems –Grasslands are so dependent on fire that its absence is considered a disturbance 36.7 Talking About Science: Ecologist Frank Gilliam discusses the role of fire in ecosystems Figure 36.7A

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Following a fire in southeastern pine forest, the numbers and variety of nonwoody plants usually increase dramatically –Fire makes more nutrients available to these plants Figure 36.7B

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A community interacts with abiotic factors, forming an ecosystem Energy flows from the sun, through plants, animals, and decomposers, and is lost as heat Chemicals are recycled between air, water, soil, and organisms 36.8 Energy flow and chemical cycling are the two fundamental processes in ecosystems ECOSYSTEM STRUCTURE AND DYNAMICS

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A terrarium ecosystem Figure 36.8 Chemical cycling (C, N, etc.) Light energy Chemical energy Heat energy

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A food chain is the stepwise flow of energy and nutrients –from plants (producers) –to herbivores (primary consumers) –to carnivores (secondary and higher-level consumers) 36.9 Trophic structure is a key factor in ecosystem dynamics

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 36.9A TROPHIC LEVEL Quaternary consumers Tertiary consumers Carnivore HerbivoreZooplankton PlantPhytoplankton Secondary consumers Primary consumers Producers A TERRESTRIAL FOOD CHAINAN AQUATIC FOOD CHAIN

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Decomposition is the breakdown of organic compounds into inorganic compounds Decomposition is essential for the continuation of life on Earth Detritivores decompose waste matter and recycle nutrients –Examples: animal scavengers, fungi, and prokaryotes Figure 36.9B

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A food web is a network of interconnecting food chains –It is a more realistic view of the trophic structure of an ecosystem than a food chain Food chains interconnect, forming food webs

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure Tertiary and secondary consumers Secondary and primary consumers Primary consumers Producers (Plants, algae, phytoplankton) Detritivores (Prokaryotes, fungi, certain animals) Wastes and dead organisms