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Transcript
Endangered species: Southern Sea Otter Beetle Southern Sea Otters: Are They Back from the Brink (邊緣) of Extinction? Species Interact in Five Major Ways • Habitat • Interspecific competition • Hunted: early 1900s • Predation • Partial recovery • Why care about sea otters? • Ethics • Tourism dollars • Keystone species Most Species Compete with One Another for Certain Resources • For limited resources • Parasitism • Mutualism • Commensalism Some Species Evolve Ways to Share Resources • Resource partitioning • Using only parts of resource • Ecological niche for exploiting resources • Using at different times • Some niches overlap • Using in different ways 1 Resource Partitioning Among Warblers (鶯) Blackburnian Warbler Black-throated Green Warbler Cape May Warbler Bay-breasted Warbler Predator‐Prey Relationships Specialist Species of Honeycreepers Yellow-rumped Warbler Most Consumer Species Feed on Live Organisms of Other Species • 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 camouflage (a) Span worm (b) Wandering leaf insect 2 warning coloration chemical warfare (d) Foul-tasting monarch butterfly (c) Bombardier beetle mimicry warning coloration (e) Poison dart frog (g) Hind wings of Io moth resemble eyes of a much larger animal. (f) Viceroy (總督) butterfly mimics monarch butterfly (h) When touched, snake caterpillar changes shape to look like head of snake. 3 Threats to Kelp Forests Purple Sea Urchin • Kelp forests: biologically diverse marine habitat • Major threats to kelp forests 1. Sea urchins 2. Pollution from water run‐off 3. Global warming Predator and Prey Interactions Can Drive Each Other’s Evolution Coevolution: A Langohrfledermaus Bat (長耳蝠) Hunting a Moth • 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 Some Species Feed off Other Species by Living on or in Them Parasitism: Trout with Blood‐Sucking Sea Lamprey (七鰓鰻; 八目鰻) • Parasitism • Parasite is usually much smaller than the host • Parasite rarely kills the host • Parasite‐host interaction may lead to coevolution 4 Mutualism: Hummingbird and Flower In Some Interactions, One Species Benefits and the Other Is Not Harmed Mutualism: Oxpeckers (牛椋鳥) Clean Rhinoceros; Anemones Protect and Feed Clownfish Commensalism: Bromeliad (鳳梨科植物) Roots on Tree Trunk Without Harming Tree • Commensalism • Epiphytes (附生植物) • Birds nesting in trees Most Populations Live Together in Clumps or Patches Population of Snow Geese • Population: group of interbreeding individuals of the same species • Population distribution 1. Clumping 2. Uniform dispersion 3. Random dispersion 5 Generalized Dispersion Patterns Populations Can Grow, Shrink, or Remain Stable • Population size governed by • • • • Births Deaths Immigration Emigration • Population change = (births + immigration) – (deaths + emigration) Trout Tolerance of Temperature Some Factors Can Limit Population Size • Range of tolerance Lower limit of tolerance No organisms Few organisms Higher limit of tolerance Abundance of organisms Few organisms No organisms • Limiting factor principle • 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 No Population Can Grow Indefinitely: J‐Curves and S‐Curves • Size of populations controlled by limiting factors: • • • • • Light Water Space Nutrients Exposure to too many competitors, predators or infectious diseases Population size • Variations in physical and chemical environment Zone of Zone of intolerance physiological stress Low Optimum range Zone of Zone of physiological intolerance stress Temperature High No Population Can Grow Indefinitely: J‐Curves and S‐Curves • Environmental resistance • All factors that act to limit the growth of a population • Carrying capacity (K) • Maximum population a given habitat can sustain 6 No Population Can Grow Indefinitely: J‐Curves and S‐Curves Logistic Growth of Sheep in Tasmania • 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 Why Do California’s Sea Otters Face an Uncertain Future? Population Size of Southern Sea Otters Off the Coast of S. California (U.S.) • Low biotic potential • Prey for orcas • Cat parasites • Thorny‐headed worms • Toxic algae blooms • PCBs and other toxins • Oil spills Exploding White-Tailed Deer Population in the U.S. Mature Male White‐Tailed Deer • 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 • Ways to control the deer population 7 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 (高過頭) • Population crash • Damage may reduce area’s carrying capacity Exponential Growth, Overshoot, and Population Crash of a Reindeer Species Have Different Reproductive Patterns (1) • Some species • • • • Species Have Different Reproductive Patterns • Other species • • • • • • • 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 Humans Elephants Many, usually small, offspring Little or no parental care Massive deaths of offspring Insects, bacteria, algae Under Some Circumstances Population Density Affects Population Size • Density‐dependent population controls • • • • Predation Parasitism Infectious disease Competition for resources 8 Population Cycles for the Snowshoe Hare and Canada Lynx Several Different Types of Population Change Occur in Nature 160 • Irruptive • Population surge, followed by crash • Cyclic fluctuations, boom‐and‐bust cycles • Top‐down population regulation • Bottom‐up population regulation • Irregular Population size (thousands) • Stable Hare Lynx 140 120 100 80 60 40 20 0 1845 1855 1865 1875 1885 1895 1905 1915 1925 1935 Year Humans Are Not Exempt from Nature’s Population Controls • Ireland • The Irish Potato Famine in 1845 Communities and Ecosystems Change over Time: Ecological Succession • Natural ecological restoration • Primary succession • Secondary succession • Bubonic plague • Fourteenth century • AIDS • Global epidemic Some Ecosystems Start from Scratch (裂隙) : Primary Succession Primary Ecological 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 9 Some Ecosystems Do Not Have to Start from Scratch: Secondary Succession Natural Ecological Restoration of Disturbed Land • Some soil remains in a terrestrial system • Some bottom sediment remains in an aquatic system • Ecosystem has been • Disturbed • Removed • Destroyed Secondary Ecological Succession in Yellowstone Following the 1998 Fire Some Ecosystems Do Not Have to Start from Scratch: Secondary Succession • Primary and secondary succession • Tend to increase biodiversity • Increase species richness and interactions among species • Primary and secondary succession can be interrupted by • • • • • Succession Doesn’t Follow a Predictable Path Fires Hurricanes Clear‐cutting of forests Plowing of grasslands Invasion by nonnative species Three Big Ideas • Traditional view • Balance of nature and a climax community 1. Certain interactions among species affect their use of resources and their population sizes. • Current view 2. There are always limits to population growth in nature. • Ever‐changing mosaic of patches of vegetation • Mature late‐successional ecosystems • State of continual disturbance and change 3. Changes in environmental conditions cause communities and ecosystems to gradually alter their species composition and population sizes (ecological succession). 10