Chapter 5: Biodiversity, Species Interactions, & Population Control Sea Otter  16-17,000 historically along Cali coast  Hunted for furs & b/c they compete for game fish  Nearly went extinct; recovering  Slow Comeback o Low biotic potential (1 pup a yr) o Orca food o Cat parasites from runoff o Thorny-headed worms from birds o Toxic algae blooms o PCBs & other toxins o Oil spills  Who Cares about Otters? o Heavy tourist draw o Keystone for kelp forest  Support hundreds of species  Algin from kelp for toothpaste, cosmetics, ice cream, & much else Interspecific Interactions  Relationships b/w different species  Affect survival & reproduction of each species  Effects noted as positive (+), negative (–), or no effect (0)  Interspecific Competition o (–/–) interaction o Species compete for a limiting resource  Not necessarily fighting  2 species eating same food o Competitive Exclusion Principle  Idea that no two species occupy exact same niche  One will have advantage over other & eliminate it  Loser migrates, adapts, or dies o Realized niche o Resource Partitioning  Reduces niche overlap  Use resources at different times, different ways, or in different places  Predation o (+/–) interaction o Predator kills & eats prey  Claws, teeth, fangs, stingers, poison, eyesight, speed, camouflage o Herbivory often a form Predation o Prey’s Defense  Physical – porcupine quills  Chemical – produce or acquire toxins, bad smell  Behavioral – hiding, fleeing, forming herds/schools, self-defense, & alarm calls o Mimicry & Coloration  Cryptic coloration – camouflage  Aposematic coloration – warning colors  Batesian mimicry – good mimics bad  Mullerian mimicry – bad mimics bad o Coevolution  Two interacting species can drive evolution of each other  Evolutionary arms race b/w predator & prey  Parasitism

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Symbiotic Relationships o Parasitism  (+/– ) interaction  Parasite feeds on the body of, or energy from host  Endoparasites – live within body of host  Ectoparasites – live on outside of host  Coevolution o Mutualism  (+/+) interaction  Nutrition/protection  Gut inhabitants  Nutrition/reproduction  Rhino & Oxpeckers  Cattle Egrets & Water Buffalo  Clownfish & Sea Anemone o Commensalism  (+/0) interaction  One benefits, other unaffected  Bird Nest in Tree  Epiphytes (air plants)  Live on stems of other trees Population Dynamics  Studies how size, density, dispersion, & age structure of populations change in response to environmental conditions  Dispersion o Environmental & social factors influence spacing of individuals in a population o Clumped Dispersion  Individuals aggregate in patches  Most common type  May be influenced by resource availability & behavior  Reproduction (more partners)  Hunting (wolves)  Food source (plants, fungi)  Protection (fish) o Uniform Dispersion  Individuals are evenly, uniformly, distributed  May be influenced by social interactions  Territoriality – animals defend area against others  Plants secrete chemicals to prevent crowding o Random Dispersion  Position of each individual is independent (random) of other individuals  Least common  Occurs in absence of strong attractions or repulsions  Population Size o Effected by…  Resource availability  Temperature  Disease organisms  Harmful chemicals  Arrival or disappearance of competitors o Determining Population Size  Count all individuals in population  Sampling techniques  Count individuals in several different areas, calculate density, then total population  Count nests or tracks in area, calculate density, then total population

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Mark Recapture Method  Capture & mark a random sample of individuals  Release; allow time for mixing  Capture 2nd set of individuals, count number marked  Calculate total population Practice Problem  Dolphins – 180 marked initially, 44 recaptured, 7 marked o Total Population = 1131

Population Changes  Birth Rate  Death Rate  Immigration Rate – coming  Emigration Rate – going  Total Population change = (Birth + Immigration) – (Death + Emigration)  Natural Population change = Birth - Death  Example  Birth = 25/1000  Immigration = 10/1000  Death = 10/1000  Emigration = 5/1000  Total Growth Rate per year? o 20/1000  If total population = 100,000; how many new individuals in next year? o 2,000  Example  Birth = 24 per 1,000  Death = 8 per 1,000  What is natural annual percent increase? o 16 per 1,000 or 1.6% o % means 100 in denominator  Growth Curves o Logistic Growth (S curve)  Fast growth; then fluctuates around (K) o Exponential Growth (J curve)  No limitations  Environmental Resistance o Combo of all limiting factors of population growth o Carrying Capacity (K)  Max population a habitat can support w/o degradation  (K) & Population Crash o Reproductive time lag leads to overshoot of (K) o Dieback occurs; can also lower (K) o (K) can change (seasons, rain drought, competitors)  Thomas Malthus (1766-1834) o An Essay on the Principle of Population (1798) o Population growth will lead to starvation, war, disease o Death rates will check population unless birth rates lower Reproductive Strategies  Survivorship Curves o Type I – high survival rates when young & decrease sharply when old o Type II – survival rates are equivalent regardless of age o Type III – high death rate when young & survival rates higher when older

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Biotic Potential o Capacity for population growth under ideal conditions o Intrinsic Rate of Increase (r)  Max rate at which population would grow w/ unlimited resources  High r values:  Reproduce early in life  Short generation times  Reproduce many times in life  Large # of offspring each time r-selected Species o Opportunists; reproduce & spread fast  Small size, fast growth, short life, many offspring, no parental care K-selected Species o Competitor; live in places near max (K)  Large size, slow growth, long life, few offspring, parental care, strong competitor Small populations & Genetic diversity woes o Genetic Problems  Increase frequency of genetic defects  Less diversity to adapt  More susceptible to disease o Examples  Founder Effect  Few individuals from a population colonize a new habitat  Demographic Bottleneck  Few individuals survive a catastrophe  Genetic Drift  Random changes in gene frequency  Some individuals may breed more often than others; their genes become more prevalent  ‘Flip a coin’  Inbreeding  Close relatives mate  Lines up recessive genes  Greatly increases risk of genetic abnormalities o Minimum Viable Population Size  Minimum size of population needed for long term survival of a species  These ideas w/ island biogeography model help to predict Population Density o Density Dependent Controls  Higher death rates w/ higher density  Predation  Parasitism  Disease transmission  Competition for food, space, mates o Density Independent Controls  Density doesn’t affect death rate  Normally abiotic factors  Floods  Hurricanes  Fire  Pollution  Habitat Destruction  Severe cold/warm weather

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Human Controls o Bubonic plague (1300s) – Bacteria from rat fleas o Ireland (1845) – Potato rot from oomycete o AIDS – Viral STD  White-Tailed Deer in U.S. o 1900 – habitat destruction & uncontrolled hunting o 1920s-30s – laws to protect deer; wolves & mountain lions nearly eliminated o Current – 25-30 mil. deer  Lyme disease carrier  Deer-vehicle accidents (1.5 mil.)  Eating garden plants & shrubs o Hunt ‘em down o Hunted in rural areas  More doe tags given to lower #s o Suburbs?  Can’t have gun nuts running around  Hired professional archers  Fence in yards  Spray predator scent  Birth control & sterilization? Ecological Succession  Gradual change in community composition in a given area over a long period of time  Just a GENERAL pathway  Two types… o Primary Succession  Begins in lifeless areas w/ no soil  Areas such as…  Lava Flow  Receding Glacier  Abandoned Road/Parking Lot  Takes a long time b/c no soil  Rock breaks down & releases nutrients by… o Physical weathering – water o Chemical weathering – rain water & atmospheric compounds o Biological weathering…  Early Successional Plants o Pioneer species attach to weathered rocks  Arrive as seed/spore brought by wind or animal  Lichens – mutualism b/w alga (photosynthesis) & fungus (protection)  Mosses – primitive plants o Pioneers Create Soil  Trap wind blown particles/detritus  Secrete mild acids that further breakdown rocks (lichens)  Mosses trap water like a sponge  Waste & dead matter from pioneers  After 100s-1000s yrs; soil may be thick & fertile enough for…  Midsuccessional Plants o Herbs, grasses, & low shrubs  Create shade; kills off lichens & mosses o Trees adapted to area arrive  Fast growing, shade intolerant  Climax or Late Succession o Shade tolerant seedlings arrive  Tall trees w/ long life spans o Mid-successions dieoff b/c seedlings shade intolerant

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Secondary Succession  Occurs after disturbance, removal, or destruction of ecosystem  Still has soil left  Beginning Anew  Seeds germinate that remain from before disturbance, or are brought from elsewhere  Much faster than primary b/c soil already present Prescribed Burning  Natural habitat not always climax community  Periodic fires can keep out late succession plants  Gets rid of fast burning plants  Small weeds & scrub brush  Maintains high native biodiversity  Florida Long Leaf Pine  150 yrs to reach 100+ feet tall adult  Live up to 500 yrs  Very Fire Resistant o Thick layers of bark o Leaves occur high off ground o Needle-like leaves o Leaves contain tannic acid  Red-Cockaded Woodpecker, Gopher Tortoise, Indigo Snake