* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project
Community Ecology, Population Ecology, and Sustainability Chapter 6 Why Should We Care about the American Alligator? Overhunted Niches Ecosystem services- gator holes, mounds, Keystone species Endangered and threatened species Alligator farms predation, clear vegetation… Fig. 6-1, p. 108 Key Concepts Factors determining number of species in a community Roles of species Species interactions Responses to changes in environmental conditions Reproductive patterns Major impacts from humans Sustainable living Community Structure and Species Diversity Physical appearance Edge effects Species diversity or richness Species abundance or evenness Niche structure Species Diversity and Ecological Stability Many different species provide ecological stability Some exceptions Minimum threshold of species diversity (10 - 40 producer species?) Many unknowns Net primary productivity (NPP) Essential and nonessential species Animation Species diversity by latitude Types of Species Native Nonnative (invasive or alien) Indicator- Keystone - Foundation Indicator Species Provide early warnings of ecosystem damage Indicator of water quality (trout) Birds as environmental indicators (affected by habitat loss, chemicals) Butterflies Amphibians Amphibians as Indicator Species Environmentally sensitive life cycle Vulnerable eggs and skin- susceptible to UV, chemicals Declining populations- 25% extinct or vulnerable - why? Life Cycle of a Frog Young frog Adult frog (3 years) sperm Tadpole develops into frog Sexual reproduction Eggs Fertilized egg development Organ formation Tadpole Egg hatches Fig. 6-3, p. 112 Possible Causes of Declining Amphibian Populations Habitat loss and fragmentation (wetland loss, deforestation,…) Prolonged drought Pollution Increases in ultraviolet radiation Parasites Overhunting - frog legs anyone? Disease Nonnative species - predators & competitors Why Should We Care about Vanishing Amphibians? Indicator of environmental health Important ecological roles of amphibians (insect control) Genetic storehouse for pharmaceuticals (painkillers, antibiotics, burn & heart disease medicines) Keystone Species What is a keystone? Keystone species play critical ecological roles a. Pollination b. Top predators c. decomposition EXAMPLES: Dung beetles, Sharks, bees, bats, wolves, alligators, Why are Sharks Important? Ecological roles of sharks Shark misconceptions Human deaths and injuries (p. 113)- (sharks kill 7 people /yr globally) Lightning is more dangerous than sharks Shark hunting and shark fins ($10K for a shark fin???) Mercury contamination Medical research Declining populations- (90 of 370 species endangered or threatened) Hunting bans: effective? Foundation Species Relationship to keystones species Play important roles in shaping communities Elephants Contributions of bats and birds Species Interactions Interspecific competition Predation Symbiosis= close long term association 2 or more species A. Parasitism + B. Mutualism + + C.Commensalism + 0 Animation Types of two species interactions animation. Animation Gause's competition experiment interaction Number of individuals Resource Partitioning and Niche Specialization Species 1 Species 2 Region of niche overlap Number of individuals Resource use Species 1 Species 2 Resource use Fig. 6-4, p. 114 Resource Partitioning of Warbler Species Fig. 6-5, p. 115 Animation Life history patterns interaction. Animation Capture-recapture method interaction. How Do Predators Increase Their Chances of Getting a Meal? Speed Senses Camouflage and ambush Chemical warfare (venom) Avoiding and Defending Against Predators Escape Senses Armor Camouflage Chemical warfare Warning coloration Mimicry Behavior strategies Safety in numbers How Species Avoid Predators “If it is small and strikingly beautiful, it is probably poisonous. If it is strikingly beautiful and easy to catch, it is probably deadly.” - E.O Wilson Span worm Wandering leaf insect camouflage Poison dart frog Bombardier beetle Foul-tasting monarch butterfly Chemical warfare / Warning Viceroy butterfly mimics monarch butterfly mimicry Hind wings of io moth resemble eyes of a much larger animal When touched, the snake caterpillar changes shape to look like the head of a snake Deceptive behavior Fig. 6-6, p. 116 Parasites Parasitism + - Hosts Inside or outside of hosts Harmful effects on hosts Important ecological roles of parasites Mutualism + + Both species benefit Pollination Benefits include nutrition and protection Mycorrhizae - fungi that helps plants extract nutrients and water from soil Gut inhabitant mutualism Examples of Mutualism Oxpeckers and black rhinoceros Mycorrhizae fungi on juniper seedlings in normal soil © 2006 Brooks/Cole - Thomson Clown fish and sea anemone Lack of mycorrhizae fungi on juniper seedlings in sterilized soil Fig. 6-7, p. 117 Commensalism + 0 Species interaction that benefits one and has little or no effect on the other Example: Small plants growing in shade of larger plants Epiphytes Forehead mites Bromeliad Commensalism Fig. 6-8, p. 118 Ecological Succession: Communities in Transition What is ecological succession? (Gradual change in species composition) Primary succession = establishment of communities on nearly lifeless ground (no soil) ex. glacier retreat, landslide, lava, abandoned parking lot Secondary succession- community disturbed, soil remains. Burned / cut forests, polluted stream, flood Animation Two types of ecological succession animation. How Predictable is Succession? Climax community concept- orderly sequence- “Balance of nature”- old school New views of equilibrium in nature- Unpredictable succession- “The modern view is that we cannot project the course of a given succession….” Natural struggles Population Dynamics: Factors Affecting Population Size Population change = (births + immigration) – (deaths + emigration) Age structure (stages) Age and population stability Limits on Population Growth Biotic potential Intrinsic rate of increase (r) (assumes unlimited resources) No indefinite population growth Environmental resistance= all the factors that limit population (capacity for growth) growth Carrying capacity (K) - determined by biotic potential & enviro resistance Population Growth Curves Population size (N) Environmental resistance Carrying capacity (K) Biotic potential Exponential growth Time (t) Fig. 6-11, p. 121 Exponential and Logistic Population Growth Resources control population growth Exponential growth - J-shaped curve Logistic growth - S-shaped curve Logistic Growth of Sheep Population Number of sheep (millions) 2.0 Overshoot Carrying Capacity 1.5 1.0 .5 1800 1825 1850 1875 1900 1925 Year Fig. 6-12, p. 121 When Population Size Exceeds Carrying Capacity Switch to new resources, move or die Overshoots Reproductive time lag Population dieback or crash Human Famines - Factors controlling human carrying capacity- technology Irish potato famine 1845 - 1 million dead has increased carrying capacity for humans Number of sheep (millions) Exponential Growth, Overshoot and Population Crash of Reindeer Population Overshoots Carrying Capacity 2,000 Population crashes 1,500 1,000 500 Carrying capacity 0 1910 1920 1930 1940 1950 Year Fig. 6-13, p. 122 Reproductive Patterns r-selected species Opportunists (mostly r-selected) Environmental impacts on opportunists K-selected species (competitors) Intermediate and variable reproductive patterns r-selected Opportunists and K-selected Species Fig. 6-15, p. 123 Positions of r-selected and K-selected Species on Population Growth Curve Number of individuals Carrying capacity K K species; experience K selection Number of individuals r species; experience r selection Time Fig. 6-14, p. 122 Human Impacts on Ecosystems Natural Capital Degradation Altering Nature to Meet Our Needs Reduction of biodiversity Increasing use of the earth's net primary productivity Increasing genetic resistance of pest species and disease causing bacteria Elimination of many natural predators Deliberate or accidental introduction of potentially harmful species into communities Using some renewable resources faster than they can be replenished Interfering with the earth's chemical cycling and energy flow processes Relying mostly on polluting fossil fuels Fig. 6-17, p. 125 Four Principles of Sustainability PRINCIPLES OF SUSTAINABILITY Fig. 6-18, p. 126 Solutions Principles of Sustainability How Nature Works Solutions: Implications of the Principles of Sustainability Runs on renewable solar energy. Rely mostly on renewable solar energy. Recycles nutrients and wastes. There is little waste in nature. Prevent and reduce pollution and recycle and reuse resources. Uses biodiversity to maintain itself and adapt to new environmental conditions. Preserve biodiversity by protecting ecosystem services and preventing premature extinction of species. Controls a species' population size and resource use by interactions with its environment and other species. Fig. 6-19, p. 126 Lessons for Us Reduce births and wasteful resource use to prevent environmental overload and depletion and degradation of resources. Lessons from Nature We are dependent on the Earth and Sun Everything is interdependent with everything else We can never do just one thing Earth’s natural capital must be sustained Precautionary Principle Prevention is better than cure Risks must be taken Animation Resources depletion and degradation interaction Animation Area and distance effects interaction.