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Biodiversity = biological diversity
Coined in 1985 for a conference, the proceedings of which were published as the book “Biodiversity”edited by E. O. Wilson.
What does it mean?
The variability among living organisms from all sources including terrestrial and aquaticsystems and the ecological complexes of which they are a part; diversity withinspecies, among species, and of ecosystems;interactions at all levels among organisms.
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
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
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
Why care about what we can’t see?
• Genetic variation enables evolutionary
change and artificial selection• Estimated 109 different genes across the Earth’s biota• Represents a largely untapped
genetic library
Scale of relationships
Molecules smallestGenesCellsOrganisms (individuals)PopulationsSpeciesCommunitiesEcosystemsBiomesBiosphere largest
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.)
Ecosystems
Ecosystem =biotic community + abiotic environment
Nutrients suchas carbon, etc.
e.g., flower + pollinator
Energy from the sun
Precipitation, etc.
Energy flow is one-way through ecosystems.
Materials (nutrients) are cycled through ecosystems.
Ecosystems
Ecosystems—1) Energy processes
Photosynthesis transforms radiant (solar)energy into chemical energy (stored as chemical bonds in sugars and carbohydrates.
CO2
O2
sugars,starchesin cells
sun plant
Ecosystems—1) Energy processes
Respiration is a step-by-step process thatallows organisms to use the energy stored the chemical bonds manufactured during photosynthesis.
sugars,starches
energy for cellular work+heat
O2
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)
Ecosystems—2) energy users
Producers capture the sun’s energy and transform it into chemical energy through photosynthesis.
plants + algae + blue-green algae
Ecosystems—2) energy users
Consumers are organisms that eat other organisms.Herbivores eat producers directly, carnivores eatother consumers.
Herbivores (grazers, primary consumers)
Examples: panda eating bamboo, bird eating nectar or flowers snail grazing on algae
Ecosystems—2) energy users
Consumers are organisms that eat other organisms.Herbivores eat producers directly, carnivores eatother consumers.
Carnivores (secondary or tertiary consumers)
Examples: limpkin eating apple snails American alligator amoeba
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 bacteriabut also scavengers suchas vultures
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.
Ecosystems—3) Energy flow
Lost as heat
Lost as heat
sun plant cow jaguar
decomposer decomposerdecomposer
Ecosystems—3) Energy flow
Lost as heat
1-5%
captured
10%
90%
10%
90%
10% 10% 10%
90% 90%90%
Lost as heat
sun plant cow jaguar
decomposer decomposer decomposer
Ecosystems—3) Energy flow
Carnivores, especially secondary or tertiary ones, are rare.
carnivores
herbivores
producers
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 (especiallybacteria) controls key steps in various cycles(see textbook examples of the nitrogen cycle,the carbon cycle, etc.)
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).
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
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
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
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
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)
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
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
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)
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
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)
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
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)
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.
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 patty
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.
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
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)
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
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
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
9 Phyla of the Animal 9 Phyla of the Animal kingdomkingdom
1)Porifera 6) Mollusca
2)Coelenterata 7) Echinoderm
3)Flatworms 8) Arthropoda
4)Roundworms 9) Chordata
5)Segmented worms
sponges radiates
annelidsmollusks& others
arthropodsnematodes& others
chordatesechinoderms
simplifiedevolutionary treefor the animal kingdom
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)
sponges radiates
annelidsmollusks& others
arthropodsnematodes& others
chordatesechinoderms
presence of tissues
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
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
sponges radiates
annelidsmollusks& others
arthropodsnematodes& others
chordatesechinoderms
presence of tissues
bilateral symmetry
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
TOL III: Animals (annelids & friends)
banana slug (mollusks)
earthworms (annelids)
leeches on a turtle
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
Adaptations to predatory life style
• Active and very mobile – Closed circulatory
systems
• Camouflage– Chromatophores in skin– http://www.youtube.com/watch
?v=SCgtYWUybIE
• Exceptional vision
• Beak to tear prey
• Arms (tentacles) to grip prey
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
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.”
Arthropoda:Makes up 75% of the animal kingdomBasic Characteristics:
hard external skeletonsegmented bodyjointed legs
Ex: beetle, milli & centipede, spider, crab
TOL: Arthropods (major groups)
• 1)1) Chelicerates – includes Chelicerates – includes spiders, mites, scorpionsspiders, mites, scorpions
• 2)2) Crustaceans – includes crabs, Crustaceans – includes crabs, shrimp, copepods, barnacles, etc.shrimp, copepods, barnacles, etc.
• 3)3) Uniramia – includes Uniramia – includes millipedes, centipedes, insectsmillipedes, centipedes, insects
• 4) Trilobites – extinct, known only 4) Trilobites – extinct, known only from fossilsfrom fossils
TOL: Arthropods (major features)
• 1)1) Body segmented internally and Body segmented internally and externallyexternally
• 2)2) Tagmosis (regional body Tagmosis (regional body specialization of groups of specialization of groups of segments: e.g., head, thorax, segments: e.g., head, thorax, abdomen)abdomen)
• 3)3) Chitinous exoskeleton (with thin Chitinous exoskeleton (with thin areas between segments)areas between segments)
• 4)4) Segmented (jointed) appendagesSegmented (jointed) appendages• 5) Cephalization well developed5) Cephalization well developed
1)1) Small sizeSmall size
AdvantagesAdvantages::
a) assists escape, movement in confined a) assists escape, movement in confined
spacesspaces
b) need smaller bits of resourcesb) need smaller bits of resources
DisadvantagesDisadvantages::
a) small surface : volume ratio, which a) small surface : volume ratio, which
leads to leads to
increased heat and water lossincreased heat and water loss
Reasons for successReasons for success
ArthropodArthropodss
2)2) ExoskeletonExoskeleton
AdvantagesAdvantages::
a) protection - much stronger than internal skeletona) protection - much stronger than internal skeleton
b) greater surface area for muscle attachmentb) greater surface area for muscle attachment
c) helps prevent desiccationc) helps prevent desiccation
DisadvantagesDisadvantages::
a) constrained movementa) constrained movement
b) problems re. growth… needs to be shedb) problems re. growth… needs to be shed
c) respiratory, sensory, & excretory issues c) respiratory, sensory, & excretory issues
(impervious layer)(impervious layer)
Reasons for successReasons for success
ArthropodArthropodss
Reasons for successReasons for successArthropoArthropodsds
3)3) Arthropodization (presence of jointed appendages)Arthropodization (presence of jointed appendages)Includes legs, antennae, mouthparts, etc.Includes legs, antennae, mouthparts, etc.
Permits fine-tuned movements, manipulation of Permits fine-tuned movements, manipulation of
food & other objects, locomotion, etc.food & other objects, locomotion, etc.
Regional specialization of body (tagmosis); e.g., Regional specialization of body (tagmosis); e.g.,
insect w/insect w/
(a) head: feeding, nerve & sensory center (a) head: feeding, nerve & sensory center
(b) thorax: locomotory center… legs, (b) thorax: locomotory center… legs,
sometimes sometimes
wingwing
(c) abdomen: specialized for reproduction & (c) abdomen: specialized for reproduction &
contains much of digestive systemcontains much of digestive system
4)4) Short life cycles - allows use of food resources Short life cycles - allows use of food resources
that may be available for only short period of that may be available for only short period of
timetime
5)5) High fecundity - typically several hundred to High fecundity - typically several hundred to
several thousand eggs (but is high mortality)several thousand eggs (but is high mortality)
Reasons for successReasons for success
ArthropodArthropodss
6)6) Wings (re. most insects)Wings (re. most insects)
AdvantagesAdvantages::
a) allow dispersal to food resourcesa) allow dispersal to food resources
b) increased potential for finding matesb) increased potential for finding mates
c) assist escape from predatorsc) assist escape from predators
d) miscellaneous: sexual displays, signalingd) miscellaneous: sexual displays, signaling
DisadvantagesDisadvantages::
a) require lots of energy to producea) require lots of energy to produce
b) can be awkward / bulkyb) can be awkward / bulky
c) windy, exposed habitats?c) windy, exposed habitats?
Arthropods: InsectsArthropods: InsectsReasons for successReasons for success
7)7) MetamorphosisMetamorphosis
AdvantagesAdvantages::
a) different life stages adapted for different habitats a) different life stages adapted for different habitats
& food& food
… … immature stages adapted for feeding & growthimmature stages adapted for feeding & growth
… … adults adapted for reproduction & dispersaladults adapted for reproduction & dispersal
b) minimizes competition between various life stagesb) minimizes competition between various life stages
DisadvantagesDisadvantages::
a) require lots of energy for drastic changesa) require lots of energy for drastic changes
b) molting difficult, potentially damaging / dangerousb) molting difficult, potentially damaging / dangerous
Arthropods: InsectsArthropods: InsectsReasons for successReasons for success
sponges radiates
annelidsmollusks& others
arthropodsnematodes& others
chordatesechinoderms
presence of tissues
bilateral symmetry
body cavitylining from thedigestive tube
TOL III: Animals (chordates and echinoderms)
echinoderms chordates
reversion to radial symmetry
body cavity lining from the digestive tube
dorsal nerve chord
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
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
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.
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
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 decomposersd) nutrient cyclers: many bacteria
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)
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?)
Benefits to humans
• Direct use value = marketable commodities– Food– Medicine– Raw materials– Recreational harvesting– Ecotourism
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
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)
Benefits to humans: raw materials
• Industrial materials:– Timber– Fibers– Resins, gums– Perfumes – Adhesives– Dyes– Oils, waxes, rubber– Agricultural chemicals
Benefits to humans: recreational harvesting
• Recreational harvesting:– Hunting– Fishing– Pets– Ornamental plants
Benefits to humans: ecotourism
• By definition based on biodiversity
• Growing portion of the tourism industry
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.
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
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
Intrinsic Value
• Biophilia = the connection that human beings subconsciously seek with the rest of life (nature) or the innate connection of humans to biodiversity
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?
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.
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
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?
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
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.
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)
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
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
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?
Redundancy in Ecosystems
Two opposing views: rivet hypothesis vs. redundancy hypothesis
rivet redundancy
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
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
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
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
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