Ecology Exam III

Fundamental niche

All resources and abiotic requirements needed for survival of a species

Competition

Interactions between organisms over the same scarce resource

Negatively; overlap

Competition: Both organisms are _____ affected interaction; Intensity of competition depends on degree of niche _____

Gause’s experiment

Studied paramecium protozoans

Abundant growth

Gause’s experiment: Species reared alone= ____ ____

Reduced

Gause’s experiment: Species reared together= both populations _____

Extinct

Gause’s experiment: Eventually one species went _____ while the other persisted

Gause’s experiment

Conclusion: Two species that are competing for the exact same resource cannot stably coexist (one species will have a slight advantage and outcompete the other)

Hutchinson’s plankton paradox

Organisms coexisting while using the same resource (not outcompeting one another to extinction)

Multiple limiting factors

Hutchinson’s plankton paradox (why not outcompete): Different species of plankton have different limiting factors

Spatial variation

Hutchinson’s plankton paradox (why not outcompete): variation in depths, shore, patches of nutrients; see different species dominating different microhabitats

Temporal variation

Hutchinson’s plankton paradox (why not outcompete): Change in season, weather; while some decline others thrive

Hutchinson’s plankton paradox

Plankton are resource and niche partitioning

Tilman’s resource competition theory

Studied algae

Tilman’s resource competition theory

R* resource concentration where birth rate=death rate (varying concentrations of limiting nutrients)

Declines

Tilman’s resource competition theory: Below R* population _____

Grows

Tilman’s resource competition theory: Above R* population ____

Breakeven

R* is the ______ for resource availability (minimum requirement for survival)

Lower

Tilman’s resource competition theory: When two species are competing for the same limiting resource, those with a _____ R* will win (it can survive at resource levels lower than its competitor)

Yes

Is competition hard to prove in natural ecosystems?

Removal experiments

Testing for competition: Removal of suspected competitor

Increases

Removal experiments: If the remaining species ______ in abundance, competition was occurring

Enrichment experiments

Testing for competition: Add more of the suspected limiting resource

Increases

Enrichment experiments: If the target species _____, that suggests that there was competition for that resource

Niche partitioning

Development of specializations that reduce competition between species (to reduce competition)

Competition Lotka-Volterra model

Tracks interactions and population number fluctuations due to competition not predation

Isocline

Population size where species has a net population growth rate of zero

4

Competition Lotka-Volterra model: __ possible ways data can be arranged

Competitive exclusion

Competition Lotka-Volterra model: Isoclines do NOT cross, _____ _____ results

Top

Competition Lotka-Volterra model: Whichever isocline is on ___ drives the other to extinction

Unstable coexistence

Competition Lotka-Volterra model: Isoclines cross; outcome depends on initial abundance (whoever starts with more organisms will survive)

Stable coexistence

Competition Lotka-Volterra model: Isoclines cross; Each limits itself more than limits the other (if one species gets too abundant competition will decrease and reverse)

Size

Lotka-volterra competition model can predict the outcomes of competition if we know how the population ___ of the 2 species will change overtime

Hubbell

Who came up with the neutral theory

Neutral theory

All species in a community are ecologically equivalent in needs and abilities; differences in abundance and distribution arise from random chance

No

Is the neutral theory reliable?

Needs

Neutral theory critiques: Not all organisms have the same ____

Disturbance; demographic randomness

Which two random processes are possible in the neutral theory?

Niche theory

Species differ in traits and requirements; competition and specialization structure communities; predictable outcome=resource competition

Identical; long term

Neutral theory critiques: Assumes species are ____; Neutrality cannot explain ____ ____ coexistence when niches strongly diverge (evidence of niche partitioning

Intraspecific competition

Types of competition: Within a species (same species competing)

Interspecific competition

Type of competition: Between species (different species competing)

Intraspecific competition

Types of competition: Common in dense populations; drives natural selection

Interspecific competition

Types of competition: Occurs when niches overlap; can lead to competitive exclusion; can lead to niche partitioning

Intraspecific competition

Types of competition: Density-dependent effect; more intense as populations approach K (explains why growth slows)

Crowding factors

Survival and reproduction decrease as density increases

Scramble competition

Resources are depleted by collective use; can reduce survival for all (no one individual directly controls resource access; sharks feeding on schooling fish)

Contest competition

Individuals directly interact to secure resources; some will benefit while others are excluded

Territories

Contest competition: Defending patches guarantee food or guarantee mates

Dominance hierarchies

Contest competition: Compete for mates and food

Direct interference

Contest competition: Harassment or physical exclusion

Allelopathy

Organisms release biochemicals to inhibit growth, survival, or reproduction of neighbors; aggressive form of competition (black walnut; costal sage)

Interference

Allelopathy is a form of ______ competition

Predation

One organism consuming another

Herbivory

Plant/algae eaten by animals

Grazers

Herbivory: Remove part of many plants (cattle eating grass)

Browsers

Herbivory: Feeds on leaves/twigs of woody plants (deer)

Carnivory

Animals consuming other animals; excerpts effort in collection

Pursuit predators

Carnivory: Chase and capture prey

Ambush Predators

Carnivory: Lie in wait for unsuspecting prey

Gradient

Many species are intermediates between ambush and pursuit

Omnivory

Consumes both meat and plants (teeth dentition; gut length; multiple collection methods depending on diet)

Scavengers

Feed on organisms that are already dead

Subdivision of carnivory

Dependent on who killed the prey

Scavengers

Who is ecologically important for nutrient cycling

Prey is consumed incrementally while still alive (often don’t kill host [loose food, shelter, and next generation])

Parasitism

Parasitoids

Intermediate between predator and parasite; only larval stages is parasitic; adults lay eggs in or on host (larvae consume host from within

Gause

Who’s experiment: Didinum (predator) feeding on Paramecium (prey)

Without intervention

Gause’s Predator-prey system: Predator quickly overconsumes prey (prey crashes, predators starve; both go extinct)

With intervention

Gause’s Predator-prey system: Periodic reintroduction of prey (typical pred-prey cycle)

Gause

Who’s conclusion: Natural predator-prey interactions require mechanisms beyond simple predation (immigration)

Too large

Provide a refuge (Gause): Predators can’t find prey (predator extinction)

Just right

Provide a refuge (Gause): Some prey survive and repopulation (long term coexistence)

Huffaker

Who’s experiment: Two mite species on oranges. Predator: Typhlodromus, prey: Eotetranychus

Huffaker

More complex system (who): Added structures for hiding only smaller mites could cross (prey survived longer, oscillation occurs)

Huffaker

Environmental complexity can stabilize predator-prey interactions

Recovery time

Influence pred-prey stability: Reproductive rates of predators vs prey

Immigration

Influence pred-prey stability: Colonization from outside patches

Escapability/refuge

Influence pred-prey stability: Presence or absence

Prey defenses

Influence pred-prey stability: Behavioral, morphological, chemical

Multiple prey system

Predator can switch between prey species when one becomes scarce

Stable

Multiple-prey systems are more _____

Recover

When the predator switches prey species the first prey population can _____

Threshold of security

If prey falls below a certain abundance, predators stop focusing on them

Paine effect

Multi-prey systems: Removal of sea star (top predator); results in mussels monopolizing space leading to other species decline

Paine effect

Predators can increase diversity by suppressing dominant competitors

Brooks and Dodson

Multi-prey systems: Pond without fish= dominated by daphnia (efficient filter feeders, outcompete copepods) Pond with fish= mix of daphnia and copepods

Estes

Multi-prey systems: With sea otters= sea otters eat sea urchins, keeping population low (kelp, fish, seals, eagles); Without sea otters= only urchins (overpopulate, kelp destroyed, habitat loss)

Keystone species

A species whose impact on community structure is disproportionately large relative to its biomass

Multiple predator system

Predators may compete for shared prey; can result in predation of one predator on the other; mathematically chaotic; most stable

Numerical response

Predator response to prey density: Change in the number of predators as prey density changes

More; increased

Numerical response: High prey density= ____ food= ____ survival

Functional response (behavioral)

Predator response to prey density: Changing in feeding rate as prey density changes (more frequent encounters with prey; reduced search time; plateau when preds are satiated)

Type I

Functional response: Linear; straight line, increasing until plateau; Predator consumes prey at a constant rate until satiated (no handling or search limitation)

Type II

Functional response: Hyperbolic (most common in nature); rapid rise, levels off gradually; predators spend increasing time handling prey as density rises; eventually limited by digestion or prey processing time

Type III

Functional response: Sigmoidal (switching and learning); S shaped curve; at low prey density predators may ignore rare prey; as prey becomes more abundant, predators switch to or learn to target them

Drives; community; easy

Predation _____ evolution; shapes ______ dynamics; predators usually target _____ prey

Prey

Predator populations are often limited by ____

Evolutionary arms race

Prey is constantly evolving to avoid predation; Predators are constantly evolving to better get/eat prey

Prey

Selective pressure on _____: camouflage, spines, toxicity, escape, morphological traits (horns, speed)