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Evolution, Biological Communities, and Biodiversity Evolution Produces Species Diversity • What are species? • How do species evolve? • Why do some species live in one place and not another? Natural selection • • • • Survival of more advantageous traits Don't confuse “more advantageous” with “better” Better for survival at that time and in that place Not universally better. Genetic Change: Mutation • Exposure to radiation • 'Typos' or errors in DNA replication Evolution is not a "Red in Tooth-and-Nail" Process • Competition is only one factor in evolution • Competition is not always violent • Its often about getting to a resource faster, etc • Cooperation can be an effective technique for adaptation and survival Selection pressures • Physiological stress (moisture, light, temp, pH, etc) • Competition among species • Predation • Luck Physiological Stress: Tolerance limits Range within which species can survive Many factors, each with corresponding ranges Example: salt level, moisture, temperature, etc Alpine Tree Line (Banff Nat Park - Canada) Critical Factor Many organisms have a limited geographical distribution because of a single factor Saguaro cactus range is strictly limited by temperature Penguin movie as an example of agedefined tolerance limits Penguins live all over the place but give birth in specific places because babies couldn't survive in other adult habitats Species as indicators Reflect certain conditions of the environment and ecosystem dynamics Trout Bull thistle Defenseless creatures Scars of Evolution We get the impression of perfect adaptation to habitat Many characteristics are “left over” from previous survival strategies In humans: toes, goosebumps Speciation – the source of Biological Diversity • Eventual split of a single species into more than one • Directional selection (ex: adaptation to toxins) • Stabilizing selection (narrow the range of a trait) • Disruptive selection (ex: Darwin's finches) “If Evolution Is True, Why Isn't It Still Going on Today?” Evolution as Ongoing • It's gradual, imperceptible except with rapidly reproducing species • We can see evolution happen in • • • • Fruit flies Anti-bacteria-resistant bacteria Pesticide-resistant insects drug-resistant microbes • Useful for bioremediation Critical View of Species Taxonomy • This system is for: • ease of communication between scientists • display in museums • not the only possible categorization scheme Species Interactions Shape Biological Communities • How do species interact? • How do these interactions shape ecosystems? Survival Strategies Survival Strategies - Generalist vs specialist • Generalist (like a rat or cockroach) has a large niche, but with lots of competitors • Specialist (like Panda) has a small niche with few competitors • Strategy affects reproductive characteristics, food habits, population size, and vulnerability to change Reducing Competition • Interspecific competition • Developing better strategies for resource use • Specialization • Intraspecific competition • Young dispersal • Territoriality • Intergenerational partitioning Competitive Exclusion • The idea that competitive species can't coexist for long • The less-skilled/adapted species must find a different niche or die out • Resource partitioning “makes room” Strategies Producers Consumers Predators (herbivores, carnivores, etc) Non-predators (scavengers, decomposers, etc) Predator-mediated competition Predators keeping successful populations in check Predatormediated competition Predator-prey relationship influences speciation Predator-prey relationship influences speciation Conceptualizing the environment Environmental systems: a network of interactions In terms of scale: Large scale (global environment) or small scale (fish bowl) As flows and storage: processes that change over time. As a closed or steady state: Mapping these flows from a distance creates the illusion of “balance” which leads to the idea of “environmental health.” Ecosystem Resilience Constancy (lack of fluctuation in composition or function) Inertia (resistance to external influences or “wobble”) Renewal (ability to repair after 'damage') Complexity Refers to the number of species in each trophic level and the number of trophic levels (trophic level: step in the flow of energy through an ecosystem – something like a step in the food chain) Tropical rainforests Ecological Structure Spatial distribution of individuals and populations within a community Three basic configurations Random Uniform (territorial bird species) Clumped (schools of fish or stands of trees) Ultimately bound by nutrient/water/energy availability Random Distribution Uniform Distribution Clumped Distribution Two Models for Understanding Ecological Communities Equilibrium model Non-equilibrium model Equilibrium Model of Ecosystem Communities Ecosystems tend toward a stable climax community A series of stages, each more complex, develops from a starting point, following disturbance Disturbance under the equilibrium model Any event or process that disrupts established patterns Both human-induced and 'natural' Pioneer species Capable of colonizing harsh environments quickly Build up soil Annuals and biennials often don't need a lot of soil Seeds disperse easily Generalists Second-stage succession Perennials (grasses, herbs, shrubs, trees) Specialists Theoretically, stability and complexity develop over time Non-Equilibrium Ecosystem Model Because conditions of evolution are constantly changing, ecosystems are unpredictable The stability of any particular configuration is an illusion resulting from a narrow frame of reference Any ecological configuration is dependent on a unique historical set of events Over the long term, perceived patterns like equilibrium become meaningless Disturbance under the non-equilibrium model What counts as disturbance changes depending on the scale of analysis Both in terms of time and space Disturbance is an inherent part of ecosystem functioning Helps lesser competitors by having a greater effect on supercompetitors Forms of Disturbance 'Natural' Disturbance Landslide Earthquake Fire Stampede Tree fall Human induced disturbance Logging Farming Forestry practices Urban growth and other land conversion Fire prevention in the US Informed by equilibrium model and organismal view Also by economic desire (for timber) Creates highly flammable landscapes Controlled burns now a common practice Fire as Disturbance Many species take advantage of fire (e.g. Manzanita) Depend on frequent fires for survival To clear competitors Prepare Enrich seeds soil Introduced Species as Disturbance Most often, introduced species fail to survive or are incorporated harmlessly Occasionally an outside species is able to outcompete all other organisms in a niche Wide-ranging effects of invasive species Extinctions Changes of other organisms in landscape Overpopulation and damage to crops Complicating the idea of Introduced Species Scale is again an important factor Succession is often a case of new species coming in to outcompete others What might really be going on our desire for a particular ecological configuration The (temporal/spatial) scale at which we understand 'ecosystem' defines what is invasive Deer – Invasive or Not? Cause damage similar to many “foreign” species Landscape Over population Extinction change of other organisms Deer aren't foreign – deer problem is a result of eradication of predators and land conversion to agriculture and "sprawl" by humans Disturbance at Ecosystem Boundaries Edges and Boundaries Ecosystem boundaries are called ecotones Energy often flows across boundaries Some birds are a good example of this The greater the flow of energy (crossing of organisms) the more “open” the ecosystem This flow of energy can disrupt ecosystem functions This disruption is called edge effect Habitat Fragmentation Habitat fragmentation threatens ecosystems by creating too much edge Biomes Biomes – broad general categories characterized by their general climatic characteristics and the kinds of organisms that thrive there Biomes have changed and moved many times during the history of life on Earth. More recently, human activities have drastically altered these communities. By understanding different biomes, we can understand the impacts of human activity on them Tropical Forest Biome Tropical Seasonal Forest Biome Savanna and Tropical Grasslands Desert Biome Sahara Desert Sonoran Desert Temperate Grasslands Temperate and Boreal Forests Tundra Freshwater Ecosystems Wetlands Oceans Coasts Coral Reefs Deltas and Estuaries Biodiversity Genetic Diversity Ecological Diversity Species Diversity Biodiversity of Species What We Know: 1.5 Million known species At least 1.5 million have not been identified – Maybe as Many as 50 Million Why the discrepancy? Hot Spots: Places of high biodiversity High numbers of endemic species Seriously threatened Hot Spots: 1.4% of the Earth's Land Surface but About Half of All Known Plant and Animal Species Hot Spots: Contain 3/4 of the world's most threatened mammals, amphibians, and birds Hot Spots: Hotspots don't cover much land, but have a lot of species, including most of those that are in danger of extinction Limits of Hot Spot Conservation: • ignores intact/non-threatened areas, which also contain threatened, endemic species • doesn't address cultural survival, which is often linked with biodiversity Why does Biodiversity Matter? Food Medicine Recovery from disturbance Ecological Services Aesthetics 1. Food Small groups of people derive most of their food from biodiverse sites Important for diversification of diet globally 2. Medicine 50% of all medicine is derived from wild species Highly effective in treating childhood leukemia 3. Recovery from Disturbance Ecosystem Resilience Constancy Inertia Renewal Constancy: (lack of fluctuation in composition or function) Inertia: (resistance to external influences or “wobble”) Renewal: (ability to restore functioning after disturbance) Greater Biodiversity means More Resilient Ecosystems 4. Ecological Services Maintenance of soil Purification of air and water Pollination of crops •Colony Collapse Disorder 1/3 of global food output depends on animal pollination Between 80% and 90% of pollination is done by domesticated bees 5. Aesthetics For some people, it's just nice to know “it's there” 6. E.O. Wilson and Hotspots Survival of hotspots enables ecological recovery after global trauma Some believe that the sixth Great Extinction is being cause by human beings Why is biodiversity being lost? Extinction = Loss of biodiversity Anthropogenic (human-induced) causes of extinction Habitat Destruction Invasive Species Pollution Population Overharvesting Habitat Destruction Invasive Species Pollution Population Overharvesting Habitat Destruction Fragmentation Reefs destroyed by cyanide, traps, and dynamite. Overharvesting Passenger Pigeon (Extinct Sept 1, 1914) Hunting "keystone" species Bycatch Everything surrounding a Mexican trawlerman's hands will go to waste; he will sell only the shrimp. Species-based solutions to Biodiversity Loss Hunting and Fishing Laws Endangered Species Act Convention on International Trade in Endangered Species (CITES) Captive Breeding Programs Restriction of hunting and fishing in late 1800s Mainly to preserve species for game Endangered Species Act (US)(1973) Regulates 'taking', import/export, commerce, and transport Protects Critical Habitat (essential for a species' survival), public or private Fraught with Controversy • What is protected and why? • List of new species of slow • Lack of funding (leading to the 'warranted but precluded' designation) • Conservation on private lands What gets protected? "Charismatic" species are overrepresented Privileges mammals over other forms of life Special Categories • Keystone species • Indicator species • Umbrella species (require large areas of land to survive. Protecting them means protecting others) • Flagship species (attract support and motivate the public) Should we spend money to save ugly creatures, bacteria and parasites? How many can we save? What determines the answer? How many should we try to save? Is this the best way to go about things? Another Political Challenge: Conservation on Private Lands Critical Habitat designation supersedes ownership Rural property owners are often demeaned as a 'backwards' or anti-environmental But land is part of people's livelihood, and owners might not be compensated for lost economic potential Controversy over removal from the list Pro: removal from list highlights success Con: exposes species to threats Difficulty of Preserving Biodiversity in "Third World" Third World Debt • 1970s energy crisis • Oil shortage • High energy prices required world nations to borrow from World Bank/IMF at high interest rd 3 • Debt is difficult or impossible to pay off • Often partially forgiven in exchange for privatization and opening markets (esp in the case of socialist states) Preserving Nature in the Third World: Debt-for-nature swaps • Conservation groups buy a country's debt in the form of reduced bonds • Debt is 'forgiven' in exchange for a commitment to preserve forests, etc Debt-for-nature problems • Doesn't overcome the underlying insecurity of Third World Nations • Accounts for a tiny portion of debt (book example: $650,000 paid off. $1 trillion is owed)