11/8 quiz Flashcards
what are the two ways predators respond to prey?
numerically or functionally
what is a numerical predator response?
predator birth rates increase and death rates increase with increased food (prey)
numerical increase in predators
this is what we’ve been talking about in class so far!
what is the functional predator response?
rate of consumption increases, typically as prey increase
how they eat their food changes as prey increase
what are the different types of functional responses?
I, II, and III
what is a I functional predator response?
increase in prey has a linear increase in number of prey consumed
rare in nature
what is a II functional predator response?
predator consume more prey as prey density increases but eventually slows and stops as animals become full
what is a III functional predator response?
initially slow start as prey numbers increase but then quick increase in number of prey consumed until slowing and levelling off
describe the type I functional predator response in terms of prey proportions
line stays straight
same proportion of prey are eaten regardless of availability
describe the type II functional predator response in terms of prey proportions
as prey increase, the proportion eaten slows as predators get full, regardless of availability
think about instantaneous rates as plot approaches levelling off
graph appears like a logistic growth curve
describe the type III functional predator response in terms of prey proportions
starts low bc low prey availability, but increases as predators get better at catching them and their density increases
what is optimal foraging theory?
organisms will maximize energy obtained when food is available
what are tradeoffs in optimal foraging?
time, quality, and risk
need to compensate for energy lost while catching prey
organisms that have to travel far for prey will obtain ___ amounts of prey in one go
large
compensating for distance
we can model oscillations of predator prey population sizes using…
zero-growth isoclines
lotka-volterra models give us ___ ___ we can test
simplifying assumptions
coexistence is determined by ___ ___
environmental factors and interactions
what is succession?
the change in species composition over time as a result of abiotic and biotic agents
what is the climax stage of succession?
the theoretical stable end point after a series of changes
this is ideal forms of each biome
ecological communities face both species ___ and ___ changes over time
richness and composition
what is primary succession?
new slate
newly formed substrates that are not yet modified by organisms
ex: lava flows, landslides, new islands, etc.
what is secondary succession?
following disturbance when soil is altered but not completely destroyed
ex: in large clearings or after fires
what is the term for a succession stage?
seral stage
what is the series of events in the theoretical model of succession?
climax + disturbance -> some life -> secondary succession -> intermediate stage -> back to climax
or
climax + disturbance -> no life -> primary succession -> pioneer stage -> intermediate stage -> back to climax
what is a climax community?
the endpoint of succession where the community is at a steady state
think the biomes
what are disturbances?
any event that disrupts a community’s structure and makes changes to the availability of resources or the physical environment
initiate change in the community
disturbance scales can…
vary
think canopy gap vs glacier retreats
what are key characteristics of disturbances?
size, intensity, and frequency
what is a ecological pioneer?
things that get there first after significant disturbance, start of primary succession
what can disturbances cause?
disruption of resource
influence growth and death rates
** many species are adapted to this
how does successional sequence affect frequency of disturbance?
early stages aren’t flammable as there isn’t much fuel on the forest floor
mid- to late stages are vulnerable to wind and insect pests that makes them prone to fires
how long does it typically take to complete a successional sequence?
about 300 years
what are the two community responses to disturbance?
resistance or resilience
what is resistance to disturbance?
how well a community can withstand a disturbance
what is resilience to a disturbance?
how quickly the community can recover from a disturbance
community stability is a function of…
disturbance’s size and relative frequency in the region
imagine blue/green/yellow graph
disturbance can also ___ ecosystems
maintain
prairies are maintained by fires to prevent other species, like trees, from dominating
what are exogenous disturbances?
ones that come from outside the ecosystem
ex: hurricanes
what are endogenous disturbances?
come from within the ecosystem
ex: herbivory by geese destroyed grassland
what can contribute to teh successional trajectory of an ecosystem?
amount and type of herbivory
wildebeest clear out tall grasses, leave room for gazelle prey species to grow
elephants grazing on African forests prevent tree growth despite it being a good area for it (and fire)
disturbance is a ___ and ___ part of all ecosystems
natural and necessary
disturbance starts and often determines…
the outcome of succession
which species are left to restart from
what results from primary succession?
extremely harsh environment
very little soil development
low nutritional availability or organic matter
what’s an example of primary succession?
krakatau after volcanic eruption
lichens began by breaking down rocks, provided surface for moss to grow and trap soil, soil accumulation allowed for seedlings to establish
which species colonized krakatau first?
sea and wind dispersed
established plants and then animals came and dispersed a lot more
what’s another example of primary succession?
grasses invading sand dune
stabilizing them and accumulating organic nutrients
grasses replaced by shrubs
shrubs replaced by trees
what results from secondary succession?
pre-disturbance remaining biota (adults, seed bank, root stock)
soil intact
higher nutrient availability
what remains during secondary succession because soil is intact?
seeds and root tissue persist from pre-disturbance organisms
what is an example of secondary succession?
NC forests cleared for timber or agriculture
regenerating forests go through a consistent and predictable pattern of succession
what are adaptations to early/late successional species?
number of seeds
seed size
dispersal method
seed viability period
what characteristics do early successional plants tend to have?
lots of small seeds
dispersal by wind or stuck to animals
long viability period or latency in soil
what characteristics do late successional plants tend to have?
few large seeds
dispersed by gravity or when eaten by animals
short seed viability period
why do plants have adaptations for early/late successional periods?
early want to grow a lot of plants and spread them far because they don’t know where good conditions will be
late can spend more energy on building up seeds and not having them travel super far because they know the conditions where they are are good
think dandelion vs oak tree (acorns)
succession usually focuses on plants, but it also impact ___
animals
think different birds can use different trees that develop over different periods of succession
what are the mechanisms to succession?
facilitation, inhibition, and tolerance
what is facilitation?
stages pave the way for the next one
ex: nitrogen fixing species add nitrogen to soils, which allows other species to live there
what is inhibition?
one species prevents others to establish themselves
succession becomes dependent on which species arrive first
ex: black walnuts make soil harder for other species to grow in around them
what is tolerance?
species are unaffected by each other
succession is dependent on dispersal abilities of an individual species and environmental characteristics
we can get different __ after different ___
ecosystems after different successions
there are about 10-13 million species on earth (not including bacteria), which are the main ones?
beetles, mites, and algae have a lot of species richness
still a lot of unknown though
what is biodiversity?
amount of variation of life forms in a given area
what are the components of species diversity?
species richness and evenness
what is species richness?
a count of all the species in a community
what is species evenness?
a measure of how common or rare each species is relative to the others in a community
how can we tell if we’ve done a good job at capturing species richness data?
species accumulation curve, see if we’ve levelled off yet
if not, need more samples
most species are pretty ___
rare
how do we calculate species abundance and evenness?
shannon-weaver diversity index
more abundance and evenness -> greater S-W index
what are the scales of species diversity?
alpha, beta, and gamma
what is alpha species diversity?
species richness of a single community in one place
usually user designed/divided (like by city, region, etc.)
what is beta species diversity?
species richness across several adjacent communities
ex: lake forest vs. libertyville
what is gamma species diversity?
species diversity among a group of different communities on a landscape scale
ex: east coast vs west coast
where are most species located?
around the equator due to latitudinal diversity gradient (except for gap due to desert having no trees)
higher latitude =
lower number of species
within a given latitude, biodiversity also varies due to…
temperature, precipitation, complexity of topography and habitat, and productivity
more elevation shifts (topography) -> more biodiversity and different habitats
also history (think mountains and glaciers)
what are the three types of hypothesis to explain patterns of biodiversity?
environmental, species-interaction, and null
what are the environmental hypotheses?
favorableness
time since perturbation
productivity
environmental heterogeneity
intermediate disturbance
what is the favorableness hypothesis?
more favorable environments will have higher biodiversity
what is the time-since-perturbation hypothesis?
environments that have not been disturbed for long periods of time will have higher biodiversity
how do the tropics use the t-s-p hypothesis?
tropics = older and more climatically stable, less disturbed (no ice ages)
more time for speciation and less extinction -> higher diversity
how do the tropics use the favorableness hypothesis?
enviros are more favorable in tropics -> less extremes -> less extinction -> higher diversity
lack of drought, frost, climate fluctuations, etc.
what is the productivity hypothesis?
environments with higher primary producer activity can sustain more species and larger populations of each species (smaller pops are more likely to become extinct)
how does the productivity hypothesis apply to the tropics?
tropics have high productivity and energy input (solar)
high amounts of primary producer output -> more resources -> more species supported
not a perfect solution, ex: desert has low prod but high div while marsh has high prod and low div
what is the environmental heterogeneity hypothesis?
environments with more types of habitats will allow for more species to coexist
how does the environmental heterogeneity hypothesis apply to the tropics?
tropics have high structural complexity and therefore more niche space
more places to hide, resources, etc.
disturbance creates…
gaps in the environment
this allows new species to colonize
resets areas
what is the intermediate disturbance hypothesis?
intermediate levels of disturbance promote diversity
too much disturbance will only allow for species that can tolerate a lot of stress while too little disturbance will allow top competitors to cominate
what are the different species interactions hypotheses?
niche diversity, overlap, and breadth
what is a niche?
the range of environmental conditions and resources that individuals of a species can persist in
competing species can coexist if they…
partition the niche
can’t coexist if there’s strong overlap
what is the niche diversity hypothesis?
environments with wider “niche space” (variety of resources) can support more species and will have higher biodiversity
expanding x-axis
what is the niche overlap hypothesis?
environments where species can tolerate more competition will have higher biodiversity
cram them closer together
what is the niche breadth hypothesis?
environments where species have narrower niches (specialists) will have higher biodiversity
this is niche partitioning
how do these species interaction hypotheses contribute to tropics have higher amounts of biodiversity?
there is more variety of roles in tropic regions (think bats in cameroon vs canada) than in higher latitude regions
competition isoclines show…
the more similar species are, the harder it is for them to coexist
must either partition or outcompete
what are key characteristics of a community?
how many resources there are?
how do species share those resources?
how much variety is there in the range of condition and resources the species can use?
what are the null models?
area and mid-domain
what is the area hypothesis?
larger areas have more species
bc the area itself is a resource
how does the area hypothesis contribute to the tropics?
widest part of earth is at the equator
how does the mid-domain hypothesis contribute to the tropics?
tropics are in the middle of earth, so the most overlap occurs there
statistical outcome related to how species ranges overlap
what is the mid-domain hypothesis?
most overlap will occur in the middle of an area because we are bound to its limits
what are some reasons the greater biodiversity in the tropics is still unresolved?
some answers cannot explain all cases
some answers explain only a small fraction of cases
probably a combination of factors that cause higher biodiversity
what comprises biodiversity?
number of species and their relative abundance
what complicates sampling of species diversity?
differences in species abundance, taxonomic confusion (inability to know how many species there are and if we’re understanding their niches correctly) and cryptic habits
species diversity increases with…
the complexity of the habitat and potential biotic interactions
