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Biodiversity, Species Interactions, and Population Control Chapter 5 Key Concepts • Species interactions • Responses to changes in environmental conditions • Factors determining number of species in a community 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 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 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. Species Interactions: Competition Interspecific Competition Fundamental niches Fighting for limited resources Competition from humans Reducing or Avoiding Competition Resource partitioning Role of natural selection Specialization and sharing of resources Resource partitioning of warblers 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 Resource Partitioning of Warbler Species 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 Deceptive behavior When touched, the snake caterpillar changes shape to look like the head of a snake 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 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. Limits on Population Growth Biotic potential (capacity for growth) Intrinsic rate of increase (r) (assumes unlimited resources) No indefinite population growth Environmental resistance= all the factors that limit population 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) 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 Year 1900 1925 When Population Size Exceeds Carrying Capacity Switch to new resources, move or die Overshoots Reproductive time lag Population dieback or crash Human Famines - Irish potato famine 1845 - 1 million dead Factors controlling human carrying capacity- technology 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 Year 1940 1950