INB 373 Exam 3

Compare Carnivore vs Herbivore diets

carnivores→ usually generalist → prey have low encounter rates and short handling times, this means they want what is available rather than being picky

herbivores→ mostly specialists→ high encounter rates but longer handling times, often focus on specific plant species or parts with higher nutritional value (seeds/leaves)

What are search and capture mechanisms of carnivores? How does prey avoid predation?

Carnivores hunt:

• active foraging (wolves, lions)

• ambush (snakes, eels)

• traps ( spiders)

Prey avoid:

• camouflage (cryptic coloration)

• mimicry (batesian & Mullerian butterflies)

• behavioral defenses (speed, grouping)

• toxins or armor

How plants avoid being eaten. How herbivores can overcome these defenses?

plants defend:

• structural defenses (thorns, tough leaves)

• chemical defenses (toxins, secondary metabolites)

Herbivores overcome by:

• tolerate or detoxify chemicals (caterpillars eating wilkweed)

• behavioral tactics (slow resin chewing by beetles to avoid plant toxin)

What does the Lotka-Volterra model show?

• prey increase when predators are few

• predators increase when prey are abundant

• both populations cycle with some lag

• Ex. Hares and lynxes

What are the factors that affect whether predator–prey populations cycle?

• predator efficiency (a)

• prey growth rate ®

• habitat complexity

• predator dispersal

• prey refuges

• evolutionary adaptations

how can predators affect prey distribution and abundance?

• reduce prey population size

• alter prey distribution

• prevent prey overpopulation

how can carnivores and herbivores alter communities in dramatic ways?

• change competitive outcomes among species

  • starfish removal led to mussel dominance

• cause trophic cascades

  • arctic foxes reduce seabirds→ changes in plant types

• be used in biocontrol

  • beetles controlling invasive weeds

why are parasites abundant and often specialists?

• depend on specific hosts for survival and reproduction

• specializing allows adapt to host defenses

• most hosts have multiple parasites— require host-specific complex

Compare and contrast ectoparasites and endoparasites

ectoparasites→ live outside the host (ticks/lice)— easier to disperse but exposed to environment

endoparasites→ live inside the host (tapeworms)— protected but harder to disperse and exposed to immune system

what are some host defenses?

• skin/exoskeleton (barriers)

• immune system (innate and adaptive)

• biochemical defenses

• behavioral defenses

• plants use chemicals, resistance genes, and immune responses

what are some parasite counter-defenses?

• avoid or suppress immune responses (plasmodium hides in RBC)

• use virus-like particles to destroy host immune cells (parasitoid wasps)

• adaptations for host entry and nutrient extraction

how can host–parasite interactions result in coevolution?

• reciprocal evolutionary change bt host and parasite

• seen in gene-for-gene systems (wheat and wheat rust)

why can host–parasite interactions result in life history trade-offs?

• adaptations to resist parasites may reduce growth or reproduction

• parasites face trade-offs bt virulence and transmission

how can parasites influence the population dynamics of hosts?

• decrease survival, growth, and reproduction

• cause population cycles

  • red grouse and nemotode in same environment→ cycling

  • red grouse + anti-parasite→ no cycling

• reduce geographic range

  • Fungal pathogen that causes chestnut blight from Asia wiped out most chestnut pop + reduced geographic range

how can simple models of host–pathogen dynamics be used to control the establishment and spread of diseases?

• track infection rates, recovery, and immunity

• predict/control outbreaks by adjusting variables (ex. transmission rate)

• aid in disease management and biocontrol

how can parasites affect the outcome of species interactions and community structure?

parasites alter:

• competition (weaken one species more than another)

• predation (sick prey easier to catch)

• community composition (ex. loss of shrimp shifts aquatic ecosystem)

how can climate change influence host–pathogen relationships?

• expand parasite ranges

• increase host susceptibility

• alter timing and intensity of infections (stress/temperature changes)

compare exploitation competition and interference competition

• exploitation comp→ indirect— species consume shared reosurces

  • plants using water or light

• interference comp→ direct— species actively prevent others from accessing resources

  • hummingbirds chasing rivals

how and why can competition vary in its intensity?

comp intensity varies with resource availability

→ more intense when resources scarce

ex. nitrogen limitation increases below-ground competition while light increases above-ground competition in plants

Describe the importance of competition within communities.

• competition influences community structure and species distribution

• comp determines which species coexist and how resources are partionined

Compare competitive exclusion principle & competitive coexistence.

• competitive exclusion principle→ two species using a limiting resources in the same way cannot coexist

• competitive coexistence: occurs when species use resources differently enough to avoid direct exclusion

What is resource (niche) partitioning?

resource/niche partitioning→ different species exploit different resources or use the same resource differently

ex. Jamaican lizards & different part of trees→ larger individuals on thicker and smaller on thinner branches

ex. cyanobacteria absorb different wavelengths

how can competition lead to character displacement and resource partitioning?

competition can drive evolutionary change→ reduces overlap in resource us

• character displacement→ species evolve differences in trait to reduce competition

  • ex. finches break size on Galapagos

• resource partitioning→ species use environment diff to reduce direct competition

Formulate the components of the Lotka–Volterra competition model (3).

• carrying capacities (K)

• growth rates ®

• competition coefficients (alpha & beta)

  • measuring effect of one species on another

Diagram and interpret the four competitive outcomes of the Lotka–Volterra competition model.

four possible outcomes:

1. one species always wins

2. the other species always wins

3. either species can win depending on starting conditions

4. stable coexistence (comp weak or equal)

how can herbivores or predators change or reverse the outcome of competition?

shift competition outcomes

predators reduce dominant competitor abundance— allowing weaker species to persist

ex. starfish (predator) stabilize mussel (prey) population— mussels can dominate ecosystem

how can the physical environment affect the outcome of competition and distribution of species?

environmental factors (light, moisture, temp) can favor one competitor over another

ex. disturbance in forest canopy opens light for sun-dependent plants

how can disturbances allow coexistence in highly asymmetrical competitive interactions?

disturbance→ disrupt dominance

ex. fugitive species (sea palm) thrive in disturbed zones where strong competitors (mussels) are removed

Compare mutualism and commensalism.

• mutualism→ both species benefit

  • bees pollinating flowers: food and reproductive aid

• commensalism→ one benefits, the other unaffected

  • birds nesting in trees

how can positive interactions form and evolve over space and time?

positive interactions evolve through repeated beneficial encounters

• overtime— mutualisms can become more specialized/obligate

• vary across environments— can be lost if costs begin to outweigh benefits

ex. fig and fig wasp→ trees rely on wasps for pollination, wasps depend on fig trees for nursery + food

how can positive interactions vary in their strength under different physical environments?

• more common in stressful environments

• less necessary in benign/resource-full conditions

Categorize different types of mutualisms.

• trophic→ exchange of energy/nutrients (mycorrhizal fungi & plants)

• habitat→ one provides shelter (shrimp provides shelter for the goby, goby provides warnings to the shrimp)

• service→ one provides a service life defense or pollination (ants defending acacia trees from herbivores and tree provides shelter)

why are mutualisms are not altruistic?

• each partner acts on own self-interest— interaction persist only if benefits>costs

• cheating (taking resources without giving back) is countered by penalties or partner choice

what are the consequences of positive interactions on the distribution and abundance of species?

mutualisms influence distribution & abundance

ex. coral reefs depend on coral-algae symbiosis

ex. deer disperse plant seeds to new areas

how can positive interactions increase species diversity in communities?

• enabling coexistence

  • cleaner fish reduce parasites on many species

• supporting foundation species that provide habitat for others

How can positive interactions affect ecosystem processes?

• mycorrhizae boost plant phosphorus uptake→ increase productivity

• cleaner fish removal leads to reduced species diversity on reefs

how do ecologists describe communities?

communities→ groups of interacting species occurring together in space and time

boundaries?

• Physical→ all species in a sand dune, mountain stream, or desert

• Biological→ all species associated with a kelp forest or a coral reef

why do ecologists use subsets of species to define communities? List some.

due to complexity, ecologist study subsets like:

• taxonomic groups (all bords)

• guilds (species using similar resource like pollinators)

• functional groups (species with similar roles— N-fixing plants)

Define and quantify species diversity and compare to biodiversity.

species diversity→ combines richness (# of species) and evenness (relative abundance of species)

biodiversity→ broader and includes genes, species, and ecosystems

rank abundance curve

→ plot the ‘proportion’ or relative abundance of each species relative to others in rank order

• show evenness

• flatter=more even

species accumulation curves

→ species richness plotted as a function of total # of individuals counted

• species richness increases with sampling effort

species composition

→ actual species present

• two communities can have similar diversity but very different species

importance? to understand community identity & function

Compare direct versus indirect species interactions.

• direct→ between two species (predation, competition)

• indirect→ mediated by a third species (trophic cascades)

how can species interactions vary in strength and direction, and how these attributes can be measured experimentally?

• strength→ magnitude vary (keystone predators like sea stars impact whole ecosystem)

• direction→ positive (mutualism), negative (competition/predation), neutral (no sig impact)

• measurement→ removal experiments

  • remove one species (interactor)

  • measure response (target)

  • difference= interaction strength

Compare foundation species, keystone species, and ecosystem engineers and the effects they have on communities.

• foundation species→ high abundance and big impact (ex. trees)

• keystone species→ low abundance, strong indirect effects (ex. sea stars)

• ecosystem engineers→ modify the environment (ex. beavers)

Define abiotic and biotic agents of change.

• abiotic agents→ non0living forces like floods, fires, storms, temperature extremes, or droughts that alter community structure

  • disturbance: events that physically injure/kill some individuals and create opp for others (short term like tsunami)

  • stress: factors that reduce growth, reproduction, or survival of individuals (long-term drought)

• biotic agents→ living factors such as predation, herbivory, disease, or the influence of keystone/ecosystem engineer species

Compare disturbance intensity with disturbance frequency.

• intensity→ how strong a disturbance is

  • how much biomass is removed

• frequency→ how often disturbances occur

  • wildfire every 5 vs 50 years

low freq & low intensity: community remain stable

high freq & high intensity: can reset succession repeatedly

intermediate levels? higher species diversity by preventing competitive exclusion + colonization

Compare primary succession with secondary succession.

• primary succession→ begins in newly exposed areas without soil— like lava flows or retreating glaciers

  • inhabited by early colonizers who are stress-tolerant and help build soil (moss, lichens)

• secondary succession→ occurs where disturbance partially destroys a community but leaves soil intact— fire, storm, logging

  • faster than primary succession bc seed baks, roots and soil organisms present

what is the early research and differential views of early ecologists with regard to succession?

• Frederic Clements (1916): viewed succession as predictable and orderly, ending in a climax community—a stable state.

• Henry Gleason (1917): argued that communities are individualistic, resulting from random colonization and environmental filtering.

• Charles Elton (1927): emphasized the role of organisms (e.g., herbivory, dispersal) in shaping succession.

What are the multiple models of succession? Compare them.

• facilitation→ early species modify environment to help later species (usually +/ -)

  • nitrogen fixation: higher soil N benefits later species

• inhibition→ early species hinder colonization by others

  • first species (green algae) prevent later species from settling in intertidal rocks bc settle quickly after disturbance

• tolerance→ all species can colonize early but later species dominate due to traits like slower growth and longevity

  • forest succession begins with forbs and grasses and later pins+oaks that outcompete early plants

Describe the 5 successional stages through the Glacier Bay (Alaska).

1. pioneer stage: begin soil formation with lichen, mosses, cyanobacteria

2. dryas stage: further improvement for later species with dryas app. (nitrogen-fixing)

3. alder stage: increase organic matter and closed canopy with alder trees

4. sitka spruce forest: more stable, complex forest forming with sitka spruce (outcompete alder)

5. western hemlock forest: dense, mature forest, extremely shade-tolerant with western hemlock trees

Summarize the results of experiments designed to determine the mechanisms of succession.

Chapin et al. at Glacier Bay

soil nutrients and organic matter increase with succession

→ spruce growth is affected by both positive (facilitation) and negative (inhibition) interactions with existing vegetation

Results? succession is driven by a mix of biological interactions (facilitation, inhibition, tolerance) and life history traits (growth rate, longevity, seed dispersal)

Define alternative stable states and stability.

• alternative stable states→ multiple community outcomes possible under the same environmental conditions

  • ex. coral reeds shifting to algae-dominated systems

• stability→

  • resilience: ability to bounce back after disturbance

  • resistance: ability to withstand change during stress

hysteresis

returning to original state may not occur even if original conditions are restored

[observed equilibrium of a state can not be predicted solely based on environmental variables but also knowledge of the systems past history]

ex. cheatgrass fire cycles

Describe how human activities have caused regime shifts.

regime shifts→ large persistent changes in ecosystem structure and function

human causes?

• climate change

• overharvesting

• invasive species

• habitat destruction

biogeography

study of the distribution of species and ecosystems across geographic space and through geological time

explain how patterns of species diversity and composition are connected across different spatial scales.

• global scale→ diversity shaped by evolutionary history, continental drift, and climate

• regional scale→ shaped by species pools (the species available to colonize local habitats)

• local scale→ influenced by biotic interactions (competition/predation) and abiotic filtering (soil/temp)

scales are nested— global patterns influence regional pools, regional pools shape local communities

Analyze the relative importance of species pools versus local scale processes in determining local community species diversity.

• species pools sets the upper limit on local diversity

• local conditions and interactions determines which species from the pool can persist

ex. tropical forest: hundreds of tress species but soil type, herbivory, light availability limit how many are found in particular patch

Describe the two major biogeographic patterns—biogeographic regions and latitudinal gradients in species diversity—at the global scale.

• biogeographic region: neartic, neotropical, paleartic, ethiopian, oriental, australasian

  • defined by continental separation and evolutionary history

• latitudinal gradient: species richness is highest at the equator and delcines toward poles

Explain the underlying forces thought to be important in creating biogeographic regions.

• contiental drift and plate tectonics

• historical climate and glacial events

• barriers— oceans, mountains, deserts

Outline the hypotheses (3) proposed to explain the latitudinal gradient in species diversity pattern.

1. tropical stability hypothesis: tropics have had longer, more stable climates, allowing more time for speciation

2. productivity hypothesis: high temperatures and moisture increase primary productivity— supporting more species

3. evolutionary rate hypothesis: warmer temps may increase mutation and speciation rates

Graph and explain the species–area relationship and know why it differs between islands and mainland areas.

SAR→ larger areas have more species due to greater habitat variety and lower extinction rates

S=cA^z

islands show steeper SAR curves than mainlands→ isolation limits immigration & smaller pops lead to more extinctions

Explain regional species diversity for islands and island-like areas using the equilibrium theory of island biogeography.

MacArthur & Wilsons theory proposes that island diveristy reuslts from a balance between: immigration rate (higher for near islands) and extinction rate (lower for large islands)

predictions?

• larger, near islands: more species

• small, far islands: fewer species

applies to trie islands and island-like habitats

how do regional species’ pools and dispersal abilities contribute to community membership?

• regional species pool provides the source of species that could colonize a local site

• dispersal determines which species can actually reach the site

• barriers (distance, isolation, human land use) limit dispersal

how do species interactions may act to include species in, or exclude species from, communities?

Biotic filter→ species must coexist with competitors, predators, mutualists, and pathogens

species can be excluded by strong competitors/predators

ex. Mussels outcompete barnacles unless predators (like sea stars) are present to reduce mussel dominance

resource partitioning

species use the same resource in different ways— allow coexistence

reduces niche overlap and competitive exclusion

ex. different warbler species forage on different parts of trees

Outline observations, experiments, and models that support resource partitioning as a mechanism of species coexistence.

• MacArthurs warblers: birds forage in different canopy zones

• phytoplankton paradox: many species coexist in nutrient-poor lakes—small scale resource variation

models show stable coexistence through slight diff resource use

Describe the role of disturbance, stress, and predation in mediating coexistence and promoting species diversity.

forces prevent competitive exclusion:

• disturbance opens space/resources (tree-fall gaps)

• stress limits dominant competitors (extreme cold/drought)

• predation/herbivory reduces dominant species (like mussels) allowing others to persist

Define and give examples of the intermediate disturbance hypothesis and its variations.

intermediate disturbance hypothesis: diversity is highest at moderate levels of disturbance

• low disturbance= dominance by a few species

• high disturbance= only fast colonizer survive

variations?

• predation-mediated coexistence (predators keep dominant competitors in check)

• positive interactions (help stress-sensitive species establish)

Define and give examples of lottery or neutral models.

lottery model→ species compete for space randomly, but all have equal chance of suces (ex. reef fish bc of limited space)

neutral model→ assumes species are functionally equivalent and random bird/death/dispersal drives diversity (diversity~chance not competitive ability)

Describe the relationships between species diversity and ecosystem functions from observations and experiments.

increased diversity → enhanced ecosystem function

where? primary productivity, nutrient cycling, resistance to invasion

ex. prairie experiments— more plant species led to higher biomass and more stable productivity

Compare the hypotheses given to explain species diversity and ecosystem function relationships.

complementarity hypothesis→ different species use resources in complementary ways leading to better overall resource use

sampling effect hypothesis→ more diverse communities are more likely to include high-functioning species by chance

both contribute to enhanced function with diversity

Describe the elements that make up a landscape and illustrate how they can influence ecological processes such as dispersal and ecosystem function.

landscape consists of a mosaic of habitat types (patches), the matrix (domant land cover), and boundaries between patches

these elements affect:

• dispersal→ movement of individuals bt patches (depend on connectivity/barriers)

• ecosystem process→ nutrient cycling, hydrology, and disturbance spread

ex. forest patches in a crop-dominated landscape influence how birds or seeds disperse

how can landscape structure be evaluated using the number and areas of the elements that make up the landscape?

• patch size, number, shape

• edge length, core area, connectivity

tools? GIS and remote sensing

larger, well-connected patches support more species and better ecosystem functions

benefits and drawbacks associated with using coarse-scale versus fine-scale characterization of a landscape.

• coarse-scale

  • pro? captures broad patterns, easier for large-scale planning

  • con? miss fine details critical to species

• fine-scale

  • pro? reveals microhabitat variation, important for species with small home ranges

  • con? more data-intensive/harder to scale up

Describe how disturbances can affect and be affected by the landscape structure.

landscape features→

• spread of disturbances like fire or disease (fuel continuity)

• recovery patterns post-disturbance (seed source proximity)

disturbance can modify landscape by:

• creating new patches (burns/clears)

• alter connectivity and heterogeneity

• feedback loops (fragmented forests burn more easily)

Describe the impacts of habitat fragmentation that lead to loss of diversity in landscapes.

smaller isolated patches support fewer species→ reduced gene flow, increase edge effects, increased local extinction

specialist and large bodied species are especially vulnerable

ex. forest fragmentation reduces bird and mammal diversity

Evaluate why fragmentation is more likely to impact higher trophic levels (predators) relative to plants and herbivores.

• require larger ranges

• depend on intact food webs

• more sensitive to edge effects

ex. carnivores like cougars or wolves disappear from small patches even if prey remain

List the factors that constitute a suitable core natural area that sustains diversity in a landscape.

• large size (support viable populations)

• minimal disturbance

• representative habitat

• connectivity (to other patches)

• environmental heterogeneity

ex. Yellostones’s large protected are supports wolves, bear, and elk

Describe the importance of buffer zones around a core natural area in designing nature reserves.

buffer zones→ reduce edge effects and human impact near core areas

how?

• allow controlled use (grazing, tourism) whole protecting the core

• help maintain core integrity, climate buffering, species spillover

Evaluate the importance of corridors in the context of environmental change.

corridors→ connect fragmented habitats, allowing gene flow, species movement, colonization

ex. wildlife overpasses/underpasses enables safe movement across highways

Evaluate how collaborative ecosystem management may lead to better solutions to preserving diversity than strictly science-based decisions.

collaborative ecosystem management leads to more inlcuive, accepted, adapted strategies

combines:

• scientific input

• stakeholder engagement

• cultural and local knowledge

ex. co-management of fisheries or forest resources in indigenous communities

Describe why iterative adjustments to land and marine reserve management policies are needed to help improve their effectiveness.

ecosystem=dynamic ~~ management=adaptive

monitoring and feedback help update strategies on new science, policy, and community feedback

adaptive management→ learning by doing and course correction

Describe the different biological levels of diversity associated with conservation biology.

• genetic→ variation within and between population

• species→ variety and abundance of species in an area

• ecosystem→ variety of ecosystems, habitats, and ecological processes

why is preserving biodiversity important?

• ecological function→ maintains productivity, nutrient cycling, pollination and stability

• human value→ food, medicine, recreation

• prevent secondary extinction→ loss of one species can impact mutualists, prey, and predators

what prompted the rapid development of the field of conservation biology? what institutions where created?

Drive? global biodiversity crisis: caused by human pop growth, human resource use, and invasive species

institutions?

• ESA: science-focused, objective

• Nature Conservancy: combines science with direct conservation action

Differentiate between the current anthropogenically enhanced rate of extinction and the long-term background extinction rate.

background: ~1 species every 200 years for mammals/birds

current: 1 species every year

100-1000X higher than historical average of extinction rates—caused by humans not natural

Describe the pathway to species extinction from changes in population growth to the disappearance of the species.

1. habitat loss/degradation

2. population decline

3. inbreeding and genetic bottlenecks

4. extinction vortex (combo of 3 above^)

5. species extinction

Describe the causes of diversity losses associated with habitat loss and degradation.

• conversion (tropical forests to agriculture)

• fragmentation (created edge effects)

• degradation (pollution, urban runoff, erosion)

Explain the underlying mechanisms determining how invasive species lead to diversity loss.

outcompete natives, spread disease, prey on or hybridize with native species

ex. white nose syndrome disease affects hibernating bats and cause invasive fungus→ dehydration, starvation and death by disturbing skin during hibernation

Explain the underlying mechanisms determining how overexploitation can lead to diversity loss.

selective pressures reduce size/reproductive rate

ex. overfishing of bluefin tuna declined population rapidly until restrictive laws were placed

Explain the underlying mechanisms determining how pollution can lead to diversity loss.

• eutrophication from nutrient runoff

• biomagnification of toxins

• plastics ingested by marine animals

• pharmaceuticals disrupt aquatic ecosystems

Describe how advances in molecular genetics have assisted with assessing genetic diversity in populations.

detect: inbreeding, bottlenecks, gene flow

ex. flroida panther genetic rescue: add Texas pumas increased diversity, tripled pop size, and reduced health defects

Evaluate the use of demographic models in projecting the fates of endangered species.

Population Viability Analysis (PVA): estimates extinction risk under different scenarios

• set harvest levels

• determine founding pop size

• identify vulnerable age classes

plan for: reintroduction, captive breeding, and management zones

why is ex situ conservation the best approach to saving a species once it appears destined for extinction?

ex situ= outside of natural habitat (zoo, botanical gardens)

last-chance species with tiny wild population→ protects vulnerable species by providing a safe space

challenges? expensive, reintroduction is difficult/impossible, limits genetic representation

why the rarity of a species may be both helpful and misleading as an indicator of its endangerment.

helpful? rare species often have small pops and narrow ranges

misleading? some species are naturally rare and not declining

What does the IUCN Red List consider?

• population size

• geographic range

• rate of decline

what are the potential benefits of using a surrogate species to help conserve habitat and other species found in that habitat?

• umbrella species→ wide-ranging, protect entire ecosystems (ex. butterfly)

• focal species→ represent varied ecological needs or threats (ex. grizzly bear→ large home ranges require extensive wilderness areas)

goal? improve efficiency by protecting multiple species indirectly

extinction vortex

self-reinforcing cycle that leads to the decline and eventual extinction of a population

Factors? Small pop size, inbreeding, genetic drift

edge effects

changes in biodiversity that occur along the boundaries between different ecosystems, known as ecotones