1. Introduction to Biodiversity ASAB – NUST Fall 2012

2. The variety of life is biological diversity.

3. Use of the term “biological diversity” in its current sense began in 1980.

4. Biodiversity = biological diversity Coined in 1985 for a conference, the proceedings of which were published as the book “Biodiversity”edited by E. O. Wilson.

5. What does it mean? The variability among living organisms from all sources including terrestrial and aquatic systems and the ecological complexes of which they are a part; diversity within species, among species, and of ecosystems; interactions at all levels among organisms.

6. From Frankel et al., 1995, The conservation of plant biodiversity.

7. Fundamental levels of organization Genetic Organismal Ecological

8. Ecological Diversity Communities of species, their interactions Communities + resources (energy, nutrients, etc.) = ecosystem Measured primarily in terms of vegetation but relative abundance of species also important No unique definition and classification at the global level

9. Organismal Diversity Individuals, species Mostly measured by numbers of species Estimated 1.7 million species described to date Estimated total number ranges from 2 to 50 million (up to 100 million) species Mostly microorganisms and insects

10. Genetic diversity Heritable variation within and between populations of organisms Encoded in the sequence of 4 base-pairs that make up DNA Arises by mutations in genes and chromosomes Very small fraction of genetic diversity is outwardly expressed

11. Why care about what we can’t see? Genetic variation enables evolutionary change and artificial selection Estimated 10 9 different genes across the Earth’s biota Represents a largely untapped genetic library

12. Ecosystems

13. Scale of relationships Moleculessmallest Genes Cells Organisms (individuals) Populations Species Communities Ecosystems Biomes Biospherelargest

14. Ecological Principles Everything is connected to everything else. Everything has to go somewhere. There is no free lunch in nature. (Or, you don’t get something for nothing.)

15. Communities Community: all of the organisms in a given area (habitat) and their interactions.

16. Ecosystems Ecosystem = biotic community + abiotic environment Nutrients such as carbon, etc. e.g., flower + pollinator Energy from the sun Precipitation, etc.

17. Ecosystems to The scale can be… very small (a leaf) very large (global)

18.  Energy flow is one-way through ecosystems.  Materials (nutrients) are cycled through ecosystems. Ecosystems

19. Ecosystems—1) Energy processes Photosynthesis Respiration

20. Ecosystems—1) Energy processes Photosynthesis transforms radiant (solar) energy into chemical energy (stored as chemical bonds in sugars and carbohydrates. CO 2 O2O2 sugars, starches in cells sun plant

21. Ecosystems—1) Energy processes Respiration is a step-by-step process that allows organisms to use the energy stored the chemical bonds manufactured during photosynthesis. sugars, starches energy for cellular work + heat O2O2

22. Ecosystems—2) energy users There are three main categories of organisms according to the ecological roles they play: 1)Producers (primary producers, autotrophs) 2)Consumers (heterotrophs) 3) Decomposers (a special type of consumer)

23. Ecosystems—2) energy users Producers capture the sun’s energy and transform it into chemical energy through photosynthesis. plants +algae +blue-green algae

24. Ecosystems—2) energy users Consumers are organisms that eat other organisms. Herbivores eat producers directly, carnivores eat other consumers. Herbivores (grazers, primary consumers) Examples: panda eating bamboo, bird eating nectar or flowers snail grazing on algae

25. Ecosystems—2) energy users Consumers are organisms that eat other organisms. Herbivores eat producers directly, carnivores eat other consumers. Carnivores (secondary or tertiary consumers) Examples: limpkin eating apple snails American alligator amoeba

26. Ecosystems—2) energy users Decomposers (detritivores) are a type of consumer that feed on dead organic matter—they can obtain this from any of the other trophic levels. fungi and many bacteria but also scavengers such as vultures

27. Ecosystems—3) Energy flow Energy flow is one-way through ecosystems. WHY?

28. Ecosystems—3) Energy flow In any energy transformation (e.g., from one trophic level* to another) there is a net loss of usable energy. *Trophic level: feeding relationships, who is eating whom.

29. Ecosystems—3) Energy flow Lost as heat sunplant cowjaguar decomposer

30. Ecosystems—3) Energy flow Lost as heat 1-5% captured 10% 90% 10% 90% 10% 90% Lost as heat sun plant cow jaguar decomposer

31. Ecosystems—3) Energy flow Carnivores, especially secondary or tertiary ones, are rare. carnivores herbivores producers

32. Ecosystems—Materials Water and elements (e.g., carbon, nitrogen) and other materials are cycled through ecosystems. They move between organic and inorganic phases by both biotic and abiotic processes. The diversity of microorganisms (especially bacteria) controls key steps in various cycles (see textbook examples of the nitrogen cycle, the carbon cycle, etc.)

33. Ecosystem Services Services provided by biodiversity that keep ecosystems functioning. Often thought of in terms of human wellbeing. Indirect-use value of biodiversity (these services are not factored into the marketplace).

34. Ecosystem Services—examples Photosynthesis Nutrient cycling Decomposition

35. Tree of Life III: Eukaryotes (Fungi and Animals) ASAB - NUST Fall 2012

36. TOL III: Fungi and Animals Fungi and animals probably share a common ancestor with choanoflagellates (collar-flagellates) based on genetic data Cell wall components and other complex biosynthetic pathways are similar between fungi and animals

37. TOL III: Fungi and Animals fungianimalschoanoflagellates single-celled protistan ancestor

38. TOL III: Fungi Primarily terrestrial No motile cells except in reproductive cells of chytrids Chitin in cell walls Unique features of chromosomes and nuclear division Dominant part of life cycle has only one set of chromosomes per nucleus

39. TOL III: Fungi Most are filamentous, multicellular; a few are unicellular (chytrids, yeasts) Oldest fossils 450-500 million years ago About 70,000 species described; estimated to be up to 1.5 million 4 lineages: chytrids, zygomycetes, ascomycetes, basidiomycetes

40. TOL III: Fungi chytrids zygosascos basidios

41. TOL III: Fungi Consumers by absorption In addition to natural sources of organic matter, can obtain nutrition from a wide variety of man-made substrates (cloth, paint, leather, waxes, jet fuel, photographic film, etc.) Food-obtaining strategies: decomposers, parasitic, predaceous, symbiotic

42. TOL III: Fungi 1)Decomposers: use dead organic matter through excretion of digestive enzymes 2)Parasitic: obtain organic matter from living cells; many cause disease this way (pathogens) 3)Predaceous: trap and kill small organisms (nematodes, protozoans) 4)Symbiotic: form mutualistic relationships with other organisms (lichens, mycorrhizae)

43. TOL III: Fungi Structure, Growth and Reproduction -usually consist of hyphae (thread- like filaments) -mass of hyphae = mycelium -grow under a wide range of conditions -reproduction mostly sexual by spores; but asexual reproduction is common

44. TOL III: Fungi fungal mycelium on wood

45. TOL III: Fungal Diversity (chytrids) Mostly aquatic Reproductive cells with a characteristic flagellum Unicellular or multicellular with a mycelium About 750 species One cause of frog die-offs

46. TOL III: Fungal Diversity (zygomycetes) Mostly decomposers, a few parasitic Multicellular, filamentous About 600 species known Best known as the bread molds About 100 species form mycorrhizae with plant roots (now thought to include many more undescribed species)

47. TOL III: Fungal Diversity (ascomycetes) Filamentous except for yeasts (unicellular) Mostly decomposers or parasitic, some predaceous or symbiotic Over 30,000 described Includes most Fungi Imperfecti (e.g., penicillium) Economic importance: yeasts (bread, beer, wine); Dutch elm disease, chestnut blight, ergots; edible fungi (truffles, morels); antibiotics

48. TOL III: Fungal Diversity ascomycetes Cordyceps scarlet cups ergot on rye

49. TOL III: Fungal diversity yeast (ascomycete) bread wine beer

50. TOL III: Fungal Diversity edible ascomycetes morels truffles

51. TOL III: Fungal Diversity (basidiomycetes) Mainly decomposers and pathogens About 25,000 species described Ca. 5,000 species involved in mycorrhizal associations Economic importance: edible (mushrooms, corn smut); poisonous; pathogens (rusts, smuts); decomposers (woodrotters)

52. TOL III: Fungal Symbionts Lichen = symbiosis with a green alga or blue-green alga (cyanobacteria) Fungal partner usually an ascomycete, usually about 90% of the lichen biomass Have a unique biology Close to 17,000 species

53. TOL III: Fungal Symbionts Mycorrhiza = symbiosis between a fungus and a plant root Important in evolution of plants and fungi; allowed exploitation of many more habitats for both partners At least 85% of plants form mycorrhizae Involves zygomycetes (endomycorrhizae) and basidiomycetes (ectomycorrhizae )

54. TOL III: Mycorrhizal diversity endomycorrhizae (zygomycetes) ectomycorrhizae (basidiomycetes)

55. TOL III: Fungi and Animals fungianimalschoanoflagellates single-celled protistan ancestor

56. Tempeh and tofu Tofu is made by coagulating soy milk and pressing the resulting curds. Although pre- made soy milk may be used, most tofu producers begin by making their own soy milk, which is produced by soaking, grinding, boiling and straining dried (or, less commonly, fresh) soybeans.soy milksoybeans Tempeh is made by a natural culturing and controlled fermentation process that binds soybeans into a cake form, similar to a very firm vegetarian burger pattyfermentationsoybeans

58. Characteristics features The original Animal Kingdom proposed by Linnaeus included the protozoans, sponges, jelly fishes, worms, crabs, insects, spiders, snails, starfishes, sharks, bony fishes, frogs, lizards, birds and mammals. In general, animals exhibit the following distinguishing characters. The animal body generally exhibits a definite symmetry, form and shape. Animals have the capacity to move from place to place in search of their necessities. Growth in animals is determined and occurs proportionately in all parts of the body. Animals are generally heterotrophic, obtaining their food from plants and other animals. Animals have the property of irritability - the capacity to respond to a stimulus. The cells, which form an animal's body do not have a cell wall. Plastids and vacuoles are generally absent and centrioles & lysosomes are present.. Animal cells cannot synthesize all the necessary amino acids, vitamins and coenzymes and as such will have to obtain them from external sources. Reserve food is glycogen.

59. TOL III: Animals (Metazoa) Multicellular consumers by ingestion Storage product is animal starch (glycogen) Most have nervous tissue and muscle tissue (which are unique to animals) Most are mobile

60. TOL III: Animals Gas exchange through aqueous medium surrounding the organism or through specialized gas exchange structures (e.g., gills or lungs) Some kind of internal circulation system present (food, gases, maintenance of proper water and mineral concentrations, waste elimination)

61. TOL III: Animals Animals arose in the oceans from single-celled protistan ancestors The earliest animals appeared at least 1 billion years ago Most modern groups of animals appeared around 600 million years ago (the Cambrian explosion) in the oceans

62. TOL III: Animals About 35 major modern lineages (phyla) and several fossil lineages of animals are known In contrast, protists have at least 16 major lineages, plants have 12 modern and 5 fossil lineages, and fungi have 4 modern lineages Over 1 million species of animals are known; >75% of these are insects

63. TOL III: Animals Of the 35 modern lineages of animals, most remain aquatic (marine) About half of the lineages are exclusively marine Only 5 lineages have adapted to land (nematodes, annelids, mollusks, arthropods and chordates represented by vertebrates) Only the nematodes, arthropods and vertebrates have diversified extensively on land

64. 64 Fig. 1a. Phylogenetic Tree for Major Phyla of Animal Kingdom

65. 65 Fig.1b. Changes in body plan added (-------)

66. 9 Phyla of the Animal kingdom 1)Porifera6) Mollusca 2)Coelenterata 7) Echinoderm 3)Flatworms8) Arthropoda 4)Roundworms9) Chordata 5)Segmented worms

67. sponges radiates annelids mollusks & others arthropods nematodes & others chordates echinoderms simplified evolutionary tree for the animal kingdom

68. TOL III: Animals (major lineages) Earliest lineage of animals is the sponges Least specialized of all animals Lack any kind of tissues Tissue = an integrated group of cells with a common structure and function (e.g., muscles, nerves)

69. sponges radiates annelids mollusks & others arthropods nematodes & others chordates echinoderms presence of tissues

70. TOL III: Animals (major lineages) The next major adaptation, after the evolution of tissues, was the split between radial vs. bilateral body symmetry Radial = parts radiate from the center, any plane through the animal creates two equal halves Bilateral = has two sides, left and right, such that a plane through the animal can be placed only one way to get two equal halves

71. TOL III: Animals (radiates) Radial symmetry an adaptation to a more sedentary lifestyle in which the organism stays in one place and meets the environment equally from all sides Radiates (or cnidarians) have stinging tentacles Include the jellyfish, sea anemones, and corals

72. sponges radiates annelids mollusks & others arthropods nematodes & others chordates echinoderms presence of tissues bilateral symmetry

73. TOL III: Animals (major lineages) Bilateral symmetry is an adaptation to a more active lifestyle in which the organism moves around to obtain food and must detect and respond to stimuli Associated with the concentration of sensory function into the head The three major groups of bilateral animals exhibit various specializations in the formation of the body cavity

74. TOL III: Animals (annelids & friends) banana slug (mollusks) earthworms (annelids) leeches on a turtle

75. Phylum Mollusca (mollusks)* Second largest animal phylum 93,000 living species (35,000 fossil species) Mostly are marine, some freshwater and terrestrial Incredible morphological diversity *Material thanks to Dr. Jeanne Serb

76. Class Gastropoda snails, slugs, sea slugs

77. Class Cephalopoda squids, octopus, cuttlefish, nautilus

78. Adaptations to predatory life style Active and very mobile –Closed circulatory systems Camouflage –Chromatophores in skin –http://www.youtube.com/watch? v=SCgtYWUybIEhttp://www.youtube.com/watch? v=SCgtYWUybIE Exceptional vision Beak to tear prey Arms (tentacles) to grip prey

79. Class Bivalvia clams, cockles, mussels, oysters, scallops

80. TOL III: Animals (arthropods & friends)

81. TOL: Arthropods (current diversity)*  regardless of how one measures diversity, the arthropods are among the most successful lineages  nearly a million described, w/ estimates of undescribed species reaching 40 million  have colonized all major habitats on earth: nearly all marine, freshwater, and terrestrial habitats *material thanks to Dr. Greg Courtney

82. TOL: Arthropods Platnick (1992): “Speaking of biodiversity is essentially equivalent to speaking about arthropods. In terms of numbers of species, other animal and plant groups are just a gloss on the arthropod scheme.” Wilson (1999): “Entomologists often are asked whether insects will take over if the human race extinguishes itself. This is an example of a wrong question inviting and irrelevant answer: insects have already taken over… Today about a billion billion insects are alive at any given time… Their species, most of which lack a scientific name, number in to the millions… The human race is a newcomer dwelling among the masses… with a tenuous grip on the planet. Insects can thrive without us, but we and most other land organisms would perish without them.”

83. Arthropoda:  Makes up 75% of the animal kingdom  Basic Characteristics:  hard external skeleton  segmented body  jointed legs  Ex: beetle, milli & centipede, spider, crab

84. TOL: Arthropods (major groups) 1)Chelicerates – includes spiders, mites, scorpions1)Chelicerates – includes spiders, mites, scorpions 2)Crustaceans – includes crabs, shrimp, copepods, barnacles, etc.2)Crustaceans – includes crabs, shrimp, copepods, barnacles, etc. 3)Uniramia – includes millipedes, centipedes, insects3)Uniramia – includes millipedes, centipedes, insects 4) Trilobites – extinct, known only from fossils4) Trilobites – extinct, known only from fossils

85. TOL: Arthropods (major features) 1)Body segmented internally and externally1)Body segmented internally and externally 2)Tagmosis (regional body specialization of groups of segments: e.g., head, thorax, abdomen)2)Tagmosis (regional body specialization of groups of segments: e.g., head, thorax, abdomen) 3)Chitinous exoskeleton (with thin areas between segments)3)Chitinous exoskeleton (with thin areas between segments) 4)Segmented (jointed) appendages4)Segmented (jointed) appendages 5) Cephalization well developed5) Cephalization well developed

86. 1)Small size Advantages: a) assists escape, movement in confined spaces spaces b) need smaller bits of resources Disadvantages: a) small surface : volume ratio, which leads to increased heat and water loss increased heat and water loss Reasons for success Arthropods

87. 2)Exoskeleton Advantages: a) protection - much stronger than internal skeleton b) greater surface area for muscle attachment c) helps prevent desiccation Disadvantages: a) constrained movement b) problems re. growth… needs to be shed c) respiratory, sensory, & excretory issues (impervious layer) Reasons for success Arthropods

88. Arthropods 3)Arthropodization (presence of jointed appendages) Includes legs, antennae, mouthparts, etc. Permits fine-tuned movements, manipulation of food & other objects, locomotion, etc. Regional specialization of body (tagmosis); e.g., insect w/ (a) head: feeding, nerve & sensory center (b) thorax: locomotory center… legs, sometimes wing wing (c) abdomen: specialized for reproduction & contains much of digestive system contains much of digestive system

89. 4)Short life cycles - allows use of food resources that may be available for only short period of time 5)High fecundity - typically several hundred to several thousand eggs (but is high mortality) Reasons for success Arthropods

90. 6)Wings (re. most insects) Advantages: a) allow dispersal to food resources b) increased potential for finding mates c) assist escape from predators d) miscellaneous: sexual displays, signaling Disadvantages: a) require lots of energy to produce b) can be awkward / bulky c) windy, exposed habitats? Arthropods: Insects Reasons for success

91. 7)Metamorphosis Advantages: a) different life stages adapted for different habitats & food … immature stages adapted for feeding & growth … adults adapted for reproduction & dispersal b) minimizes competition between various life stages Disadvantages: a) require lots of energy for drastic changes b) molting difficult, potentially damaging / dangerous Arthropods: Insects Reasons for success

92. sponges radiates annelids mollusks & others arthropods nematodes & others chordates echinoderms presence of tissues bilateral symmetry body cavity lining from the digestive tube

93. TOL III: Animals (chordates and echinoderms) echinodermschordates reversion to radial symmetry body cavity lining from the digestive tube dorsal nerve chord

94. TOL III: Animals (echinoderms) starfish sea urchins

95. TOL III: Animals (chordates) Chordates include all animals with a dorsal nerve cord About 50,000 species total –Tunicates –Hagfishes –Amphioxus –Vertebrates: fishes, amphibians, reptiles, birds and dinosaurs, mammals

96. TOL III: Animals (chordates) tunicates or sea squirts

97. TOL III: Animals (vertebrates) fishes birds and dinosaurs reptiles and amphibians mammals

98. TOL: Summary 1)Close to 2 million species of organisms have been described. 2)Estimates of total diversity range from 10 to 50 (in one case, up to 100) million species (with very conservative estimates as low as 5 million) 3)Species diversity in several groups, primarily micoorganisms, is grossly understudied and underestimated; among multicellular eukaryotes, fungi and nematodes are also relatively unknown

99. TOL: Summary 4) Prokaryotes ruled the world long before eukaryotes evolved; prokaryotes exhibit a wide array of metabolic diversity and so control key steps in many nutrient cycles. 5) Evolutionary trees of major groups provide frameworks for understanding the evolutionary history and major adaptive changes in those groups.

100. TOL: Summary 6) The ecological function of diversity can be subdivided by roles: a) primary producers: some bacteria (e.g., cyanobacteria; aquatic), some archaens (aquatic), algae (aquatic), plants (aquatic and terrestrial) b) consumers: some bacteria and archeans, protozoans, fungi, animals; includes pathogens and predators

101. TOL: Summary 6) cont’d. c) decomposers: primarily bacteria and fungi, also some fungus-like protists, as well as some animals such as nematodes; a few vertebrate carrion-eaters could also be considered as decomposers d) nutrient cyclers: many bacteria

102. TOL: Summary 6) cont’d. e) symbionts: diverse, many kinds of organisms are involved; includes mycorrhizae (plant root + fungus), endosymbionts (e.g., corals, dinoflagellates), lichens (cyanobacteria or green alga + fungus)

103. Arthropods rule!

104. Value and Maintenance of Biodiversity ASAB – NUST Fall 2012

105. Value and Maintenance Benefits to humans, direct or indirect Intrinsic value What kind of a world do we want to live in? Redundancy in ecosystems (how much is enough?)

106. Benefits to humans Direct use value = marketable commodities –Food –Medicine –Raw materials –Recreational harvesting –Ecotourism

107. Benefits to humans: food About 3,000 species (ca. 1% of 300,000 total) of flowering plants have been used for food About 200 species have been domesticated Wild relatives source of genes for crop improvement in both plants and animals

108. Benefits to humans: medicine Organisms as chemists About 25% of all medical prescriptions in the U.S. are based on plant or microbial products or on derivatives or on synthetic versions Some medicinal products from animals (e.g., anticoagulant from leeches)

109. Benefits to humans: raw materials Industrial materials: –Timber –Fibers –Resins, gums –Perfumes –Adhesives –Dyes –Oils, waxes, rubber –Agricultural chemicals

110. Benefits to humans: recreational harvesting Recreational harvesting: –Hunting –Fishing –Pets –Ornamental plants

111. Benefits to humans: ecotourism By definition based on biodiversity Growing portion of the tourism industry

112. Indirect Use Value Indirect use value = services provided by biodiversity that are not normally given a market value (often regarded as free) Include primarily ecosystem services: atmospheric, climatic and hydrological regulation; photosynthesis; nutrient cycling; pollination; pest control; soil formation and maintenance, etc.

113. Indirect Use Value Biosphere 2 was an attempt to artificially create an ecosystem that would sustain human life Ca. US$200 million invested in design and construction plus millions more in operating costs Could not sustain 8 humans for two years

114. Intrinsic value Simply because it exists Moral imperative to be good stewards, the preservation of other life for its own sake Supported in many different religious or cultural traditions Recognized in the Convention on Biodiversity

115. Intrinsic Value Biophilia = the connection that human beings subconsciously seek with the rest of life (nature) or the innate connection of humans to biodiversity

116. Intrinsic Value Biophilia = the connection that human beings subconsciously seek with the rest of life (nature) or the innate connection of humans to biodiversity Should we put a monetary value on everything?

117. Intrinsic Value Biophilia = the connection that human beings subconsciously seek with the rest of life (nature) or the innate connection of humans to biodiversity Should we put a monetary value on everything? If something can be valued, it can be devalued.

118. What kind of a world do we want to live in? Human co-opt about 40% of the net primary productivity on an annual basis Human population at over 6 billion and growing at about 80 million per year Loss of some biodiversity is inevitable

119. What kind of a world do we want to live in? Current extinction rate much higher than background; also commitment to extinction Extinction is forever; species may have unforeseen uses or values (e.g., keystone species, medicinal value, etc.) Biodiversity has recovered after previous mass extinctions, but are we also eliminating that possibility by severely restricting conditions conducive to evolution?

120. What kind of a world do we want to live in? If 6 billion people consume 40% of the annual net primary productivity, what is the theoretical limit (= carrying capacity) for humans under current conditions? 2.5 x 6 billion = 15 billion

121. What kind of a world do we want to live in? But this number does not factor in the costs of dealing with wastes or non- renewable resources. Nor does it leave room for other biodiversity, upon which we depend for ecosystem services (such as waste removal/recycling). Human population is expected to reach ca. 12 billion by 2050.

122. What kind of a world do we want to live in? This is why many now argue that we have to find a way to put biodiversity into the economic equation Previously no monetary values were associated with natural resources except the actual ones generated by extraction (the world is there for us to use)

123. What kind of a world do we want to live in? Extraction costs (e.g., labor, energy) usually computed But cost of replacement not included, nor costs of the loss of the services provided by that resource or its ecosystem (e.g., cutting forest for timber) Because costs are undervalued, benefits of extraction are overvalued

124. What kind of a world do we want to live in? Green accounting proposed as part of the solution But requires that environmental assets have proper prices (p. 171, Chichilnisky essay in text) Tie in to property rights for natural resources

125. Redundancy in Ecosystems Or, how much biodiversity is enough? How much redundancy is built into ecological processes/communities? To what extent do patterns of diversity determine the behavior of ecological systems?

126. Redundancy in Ecosystems Two opposing views: rivet hypothesis vs. redundancy hypothesis rivet redundancy

127. Redundancy in Ecosystems Rivet hypothesis: most if not all species contribute to the integrity of the biosphere in some way Analogy to rivets in an aircraft—there is a limit to how many can be removed before the structure collapses Progressive loss of species steadily damages ecosystem function

128. Redundancy in Ecosystems Redundancy hypothesis: species richness is irrelevant; only the biomass of primary producers, consumers and decomposers is important Life support systems of the planet and ecological processes will generally work fine with relatively few species

129. Redundancy in Ecosystems In the past (from fossils), most ecological systems have been conspicuously less species rich But no evidence that they operated any differently

130. Redundancy in Ecosystems Major patterns of energy flow and distribution of biomass in existing ecological systems may be broadly insensitive to species numbers But systems with higher diversity and more kinds of interactions may be more buffered from fluctuations Lack of data regarding the link between species-richness and ecosystem function

131. Redundancy in Ecosystems Middle ground: ecosystem processes often but not always have considerable redundancy built into them –Not all species are equal (e.g., functional groups, keystone species) –The loss of some species is more important than the loss of others –Species loss may be tolerated up to some critical threshold