1. 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

2. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Wasps and Pieris caterpillars form an unusual three-step food chain The 4-mm-long wasp Apanteles glomeratus stabs through the skin of a Pieris rapae caterpillar and lays her eggs –The caterpillar will be destroyed from within as the wasp larvae hatch and nourish themselves on its internal organs Dining In

3. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Ichneumon wasps can detect when a Pieris caterpillar contains Apanteles larvae –A female ichneumon will pierce the caterpillar and deposit her own eggs inside of the Apanteles larvae

4. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Finally, yet another wasp, a chalcid, may lay its eggs inside the ichneumon larvae Usually, only the chalcids will emerge from the dead husk of the caterpillar

5. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A biological community derives its structure from the interactions and interdependence of the organisms living within it Ecosystem functioning depends on the complex interactions between its community of organisms and the physical environment

6. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings All the organisms in a particular area make up a community A number of factors characterize every community –Biodiversity –The prevalent form of vegetation –Response to disturbances –Trophic structure (feeding relationships) 36.1 A community is all the organisms inhabiting a particular area Figure 36.1

7. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Biodiversity is the variety of different kinds of organisms that make up a community Biodiversity has two components –Species richness, or the total number of different species in the community –The relative abundance of different species

8. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Interspecific competition occurs between two populations if they both require the same limited resource A population's niche is its role in the community –The sum total of its use of the biotic and abiotic resources of its habitat 36.2 Competition may occur when a shared resource is limited STRUCTURAL FEATURES OF COMMUNITIES

9. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The competitive exclusion principle –Populations of two species cannot coexist in a community if their niches are nearly identical Figure 36.2 High tide Chthamalus Balanus Low tide Ocean

10. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Competition between species with identical niches has two possible outcomes –One of the populations, using resources more efficiently and having a reproductive advantage, will eventually eliminate the other –Natural selection may lead to resource partitioning

11. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Predation is an interaction where one species eats another –The consumer is called the predator and the food species is known as the prey Parasitism can be considered a form of predation 36.3 Predation leads to diverse adaptations in both predator and prey

12. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings As predators adapt to prey, sometimes natural selection also shapes the prey's defenses This process of reciprocal adaptation is known as coevolution –Example: Heliconius and the passionflower vine Figure 36.3A Eggs Sugar deposits

13. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Prey gain protection against predators through a variety of defense mechanisms –Mechanical defenses, such as the quills of a porcupine

14. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Chemical defenses are widespread and very effective –Animals with effective chemical defenses are often brightly colored to warn predators –Example: the poison-arrow frog Figure 36.3B

15. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Camouflage is a very common defense in the animal kingdom –Example: the gray tree frog Figure 36.3C

16. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Batesian mimicry occurs when a palatable or harmless species mimics an unpalatable or harmful one –The mimicry can even involve behavior –This hawkmoth larva puffs up its head to mimic the head of a snake Figure 36.3D

17. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Müllerian mimicry is when two unpalatable species that inhabit the same community mimic each other –Example: the cuckoo bee and the yellow jacket Figure 36.3E

18. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A keystone species exerts strong control on community structure because of its ecological role A keystone predator may maintain community diversity by reducing the numbers of the strongest competitors in a community –This sea star is a keystone predator 36.4 Predation can maintain diversity in a community Figure 36.4A

19. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Predation by killer whales on sea otters, allowing sea urchins to overgraze on kelp –Sea otters represent the keystone species Figure 36.4B

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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

26. 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

27. 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

28. 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

29. 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

30. 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

31. 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

32. 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

33. 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

34. 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 36.10 Food chains interconnect, forming food webs

35. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 36.10 Tertiary and secondary consumers Secondary and primary consumers Primary consumers Producers (Plants, algae, phytoplankton) Detritivores (Prokaryotes, fungi, certain animals) Wastes and dead organisms

36. 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 36.11 Energy supply limits the length of food chains

37. 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 36.11 Tertiary consumers Secondary consumers Primary consumers Producers 10 kcal 100 kcal 1,000 kcal 10,000 kcal 1,000,000 kcal of sunlight

38. 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 3 - 5 levels –There is simply not enough energy at the very top of an ecological pyramid to support another trophic level

39. 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 36.12 Connection: A production pyramid explains why meat is a luxury for humans

40. 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 36.12 Secondary consumers Primary consumers Producers Human vegetarians Corn Human meat-eaters Cattle Corn TROPHIC LEVEL

41. 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 36.13 Chemicals are recycled between organic matter and abiotic reservoirs

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

43. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Heat from the sun drives the global water cycle –Precipitation –Evaporation –Transpiration 35.14 Water moves through the biosphere in a global cycle

44. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 36.14 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

45. 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 36.15 The carbon cycle depends on photosynthesis and respiration

46. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 36.15 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

47. 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 – ) 36.16 The nitrogen cycle relies heavily on bacteria

48. 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

49. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 36.16 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

50. 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 36.17 The phosphorus cycle depends on the weathering of rock

51. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 36.17 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

52. 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 1963 36.18 Connection: Ecosystem alteration can upset chemical cycling ECOSYSTEM ALTERATION

53. 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

54. 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

55. 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

56. 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

57. 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 36.19 Talking About Science: David Schindler talks about the effects of nutrients on freshwater ecosystems

58. 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

59. 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

60. 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

61. 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 36.20 Connection: Zoned reserves are an attempt to reverse ecosystem disruption

62. 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

63. 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 36.20 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