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MILLER/SPOOLMAN LIVING IN THE ENVIRONMENT 17TH Chapter 5 Biodiversity, Species Interactions, and Population Control How Wolves Change Rivers • Summarize the effects of the reintroduction of wolves to Yellowstone National Park. • Be specific: • What changes have been seen with regards to plants, animals, and physical landscape? • What type of species is the wolf? • Chapter 4 • Summarize this series of events on an index card. • Use specific, detailed language. 5-1 How Do Species Interact? • Concept 5-1 Five types of species interactions— competition, predation, parasitism, mutualism, and commensalism—affect the resource use and population sizes of the species in an ecosystem. Principle of Competitive Exclusion • No two species can occupy the same ecological niche for long. • The species that is more efficient in using available resources will exclude the other. • The other species disappears or develops a new niche, exploiting resources differently. • Resource Partitioning Species Interact in Five Major Ways • Interspecific Competition • Members of two or more species interact to gain access to the same limited resources, such as food water, light, and space. • Predation • A member of one species (the predator) feeds directly on all or part of a member of another species (the prey). • Parasitism • One organism (the parasite) feeds on another organism, usually by living on or in the host. • Mutualism • An interaction that benefits both species by providing each with food, shelter, or some other resource. • Commensalism • An interaction that benefits one species but has little of no effect on the other. With a partner … • Come up with two examples of each type of species interaction. • Write them down to share. Resource Partitioning Among Warblers Fig. 5-2, p. 106 Most Consumer Species Feed on Live Organisms of Other Species (2) • Prey may avoid capture by 1. Run, swim, fly 2. Protection: shells, bark, thorns 3. Camouflage 4. Chemical warfare 5. Warning coloration 6. Mimicry 7. Deceptive looks 8. Deceptive behavior Camouflage (a) Span worm Fig. 5-5a, p. 109 Camouflage (b) Wandering leaf insect Fig. 5-5b, p. 109 Chemical warfare (c) Bombardier beetle Fig. 5-5c, p. 109 Chemical Warfare+Warning Coloration (d) monarch butterfly Fig. 5-5d, p. 109 Chemical Warfare+Warning Coloration (e) Poison dart frog Fig. 5-5e, p. 109 Biomimicry (f) Viceroy butterfly Fig. 5-5f, p. 109 Deceptive looks (g) Io moth Fig. 5-5g, p. 109 Deceptive behavior: When touched, snake caterpillar changes shape to look like head of snake. (h) Snake caterpillar Fig. 5-5h, p. 109 Biomimicry • The Indonesian Mimic Octopus Do all predators kill their prey? Explain. Predator and Prey Interactions Can Drive Each Other’s Evolution • Intense natural selection pressures between predator and prey populations • Coevolution • Interact over a long period of time • Bats and moths: echolocation of bats and sensitive hearing of moths Coevolution: A Langohrfledermaus Bat Hunting a Moth Fig. 5-6, p. 110 Some Species Feed off Other Species by Living on or in Them • Parasitism • Parasite is usually much smaller than the host • Parasite rarely kills the host • Parasite-host interaction may lead to coevolution Parasitism: Trout with Blood-Sucking Sea Lamprey Fig. 5-7, p. 110 In Some Interactions, Both Species Benefit • Mutualism • Nutrition and protection relationship • Gut inhabitant mutualism • Not cooperation: it’s mutual exploitation Mutualism: Hummingbird and Flower Fig. 5-8, p. 110 Mutualism: Oxpeckers Clean Rhinoceros; Anemones Protect and Feed Clownfish Fig. 5-9, p. 111 In Some Interactions, One Species Benefits and the Other Is Not Harmed • Commensalism • Epiphytes • Birds nesting in trees Commensalism: Bromiliad Roots on Tree Trunk Without Harming Tree Fig. 5-10, p. 111 Catching up on HW … • #2, p. 122 • Another one to do now: #3 p. 123 5-2 What Limits the Growth of Populations? • Concept 5-2 No population can continue to grow indefinitely because of limitations on resources and because of competition among species for those resources. Science Focus: Threats to Kelp Forests • Kelp forests: biologically diverse marine habitat • Major threats to kelp forests 1. Sea urchins 2. Pollution from water run-off 3. Global warming • Kelp Forest Facts (NOAA) Purple Sea Urchin Fig. 5-A, p. 108 Science Focus: Why Do California’s Sea Otters Face an Uncertain Future? • Low biotic potential • Prey for orcas • Cat parasites • Thorny-headed worms • Toxic algae blooms • PCBs and other toxins • Oil spills Population Size of Southern Sea Otters Off the Coast of Southern California Fig. 5-B, p. 114 Most Populations Live Together in Clumps or Patches (1) • Population: group of interbreeding individuals of the same species • Population distribution 1. Clumping 2. Uniform dispersion 3. Random dispersion Most Populations Live Together in Clumps or Patches (2) • Why clumping? 1. Species tend to cluster where resources are available 2. Groups have a better chance of finding clumped resources 3. Protects some animals from predators 4. Packs allow some to get prey Generalized Dispersion Patterns Fig. 5-12, p. 112 Populations Can Grow, Shrink, or Remain Stable (1) • Population size governed by • • • • Births Deaths Immigration Emigration • Population change = (births + immigration) – (deaths + emigration) Populations Can Grow, Shrink, or Remain Stable (2) • Age structure • Pre-reproductive age • Reproductive age • Post-reproductive age Factors That Can Limit Population Size • Range of tolerance • Variations in physical and chemical environment • Limiting factor principle (Index Card) • Too much or too little of any physical or chemical factor can limit or prevent growth of a population, even if all other factors are at or near the optimal range of tolerance. • Precipitation • Nutrients • Sunlight, etc. Trout Tolerance of Temperature Fig. 5-13, p. 113 For humans, what is an example of a range of tolerance for a physical environmental factor? No Population Can Grow Indefinitely: J-Curves and S-Curves (1) • Size of populations controlled by limiting factors. • • • • • • • Precipitation Soil nutrients Light Space Temperature Dissolved oxygen content (aquatic systems) Salinity—amounts of salts dissolved in water (aquatic systems) No Population Can Grow Indefinitely: J-Curves and S-Curves (2) • Environmental resistance • All factors that act to limit the growth of a population • Carrying capacity (K) • Maximum population a given habitat can sustain indefinitely. No Population Can Grow Indefinitely: J-Curves and S-Curves (3) • Exponential growth • Starts slowly, then accelerates to carrying capacity when meets environmental resistance • Logistic growth • Decreased population growth rate as population size reaches carrying capacity Logistic Growth of Sheep in Tasmania Fig. 5-15, p. 115 Questions • Is the carrying capacity of an area for a given species fixed? Why or why not? • What is the carrying capacity of the earth for humans? • • • • Have we reached it? Will we ever? What could lead to an increased carrying capacity? Decreased? Thomas Malthus, 1766-1834 • Humans need certain resources (e.g., air, food, water, and shelter). A sustainable habitat is one in which supply of and demand for these resources are balanced. • The problem is the difference in growth patterns between the human population and food production. • The human population tends to grow exponentially • The food supply will only grow linearly. • In this model, humans are bound to outgrow the Earth's resources. • Many have argued that Malthus was wrong because he did not take into account human technology, but even that is being called into question by some. Case Study: Exploding White-Tailed Deer Population in the U.S. • 1900: deer habitat destruction and uncontrolled hunting • 1920s–1930s: laws to protect the deer • Current population explosion for deer • Spread Lyme disease • Deer-vehicle accidents • Eating garden plants and shrubs • Why the population explosion? Population Graphs: White-Tailed Deer When a Population Exceeds Its Habitat’s Carrying Capacity, Its Population Can Crash • A population exceeds the area’s carrying capacity • Reproductive time lag may lead to overshoot • Population crash • Damage may reduce area’s carrying capacity Species Have Different Reproductive Patterns (1) • Some species (such as?): • Many, usually small, offspring • Little or no parental care • Massive deaths of offspring Species Have Different Reproductive Patterns (2) • Other species (such as?): • • • • • Reproduce later in life Small number of offspring with long life spans Young offspring grow inside mother Long time to maturity Protected by parents, and potentially groups r-selected and K-selected species Under Some Circumstances Population Density Affects Population Size • Density-dependent population controls • • • • Predation Parasitism Infectious disease Competition for resources Are modern humans exempt from nature’s population controls? Humans Are Not Exempt from Nature’s Population Controls • Ireland • Potato crop in 1845 • Bubonic plague • Fourteenth century • AIDS • Global epidemic 5-3 How Do Communities and Ecosystems Respond to Changing Environmental Conditions? • Concept 5-3 The structure and species composition of communities and ecosystems change in response to changing environmental conditions through a process called ecological succession. Communities and Ecosystems Change over Time: Ecological Succession • Natural ecological restoration • Primary succession • Secondary succession • Video: What’s the difference? Some Ecosystems Start from Scratch: Primary Succession • No soil in a terrestrial system • No bottom sediment in an aquatic system • Takes hundreds to thousands of years • Need to build up soils/sediments to provide necessary nutrients • Example of what would lead to primary succession? Primary Ecological Succession Fig. 5-19, p. 119 Primary Ecological Succession Some Ecosystems Do Not Have to Start from Scratch: Secondary Succession (1) • Some soil remains in a terrestrial system • Some bottom sediment remains in an aquatic system • Ecosystem has been • Disturbed • Removed • Destroyed Natural Ecological Restoration of Disturbed Land Fig. 5-20, p. 120 Secondary Succession Secondary Ecological Succession in Yellowstone Following the 1998 Fire Fig. 5-21, p. 120 Some Ecosystems Do Not Have to Start from Scratch: Secondary Succession (2) • Primary and secondary succession • Tend to increase biodiversity • Increase species richness and interactions among species • Primary and secondary succession can be interrupted by • • • • • Fires Hurricanes Clear-cutting of forests Plowing of grasslands Invasion by nonnative species Succession Doesn’t Follow a Predictable Path • Traditional view • Balance of nature and a climax community • Current view • Ever-changing mosaic of patches of vegetation • Mature late-successional ecosystems • State of continual disturbance and change Living Systems Are Sustained through Constant Change • Inertia, persistence • Ability of a living system to survive moderate disturbances • Resilience • Ability of a living system to be restored through secondary succession after a moderate disturbance • Some systems have one property, but not the other: tropical rainforests Krakatau • How high did the ash, rock and magma rise during the volcanic eruption at Krakatau? What about the sulfates and dust? How would the local and global impacts from these different sorts of particles have differed? • How did most species colonize Krakatau in the first months following the eruption? Give examples of three species that tend to be early colonizers. • How did larger species reach the island after the volcano erupted (reptiles, amphibians, mammals, large insects)? Describe four means of transport for larger species. Krakatau, cont. • Describe the pattern of plant colonization on Rakata. How do Rakata’s forests differ from other Indonesian island forests today? • Describe an example from the text that shows inertia (persistence) in nature. Then describe an example that shows resilience. Three Big Ideas 1. Certain interactions among species affect their use of resources and their population sizes. 2. There are always limits to population growth in nature. 3. Changes in environmental conditions cause communities and ecosystems to gradually alter their species composition and population sizes (ecological succession).