Ecology Flashcards
What are the three cells and their intermediate points in order from the north pole to the equator?
Polar Cell
- polar front
Ferrel Cell
- subtropical high
Hadley Cell
- equatorial low
- Pressure ____ at high altitudes
- Warm air holds ____ water than cold air
decreased
more
What is the coriolis effect?
The Earth’s rotation causes moving bodies at its surface to be deflected, means that wind-driven ocean currents turn right in the Northern Hemisphere, and left in the Southern Hemisphere.
How do rain shadows occur?
Humid damp air rises from the ocean and begins ascending a mountain. The higher the air rises, the colder and less pressured it becomes and it begins to dispel it’s water. By the time passes the apex of the mountain and begins falling as it warms itself it draws up the moisture from the ground. Thus the ocean-facing side is very wet and the opposite side will be dried
Describe the continental effect
- a phenomenon that causes temperatures in inland areas to fluctuate more than temperatures near to large bodies of water.
- landmasses cool air faster than coastal areas, the costal areas see cooler summers and warmer winters,
- the more inland you get the more oppositely the effect self imposes
What are the characteristics of a tropical rainforest?
- High heat
- High precip.
- High biological diversity
What are the characteristics of a temperate forest?
- Medium heat
- Medium precip.
- High biological diversity
What are the characteristics of a boreal forest?
- Colder heat
- Medium precip.
- Medium biological diversity
What are the characteristics of a temperate grassland?
- Medium heat
- Low precip.
- Medium biological diversity
What are the characteristics of a tundra?
- Dry
- Cold
- Somewhat biologically diverse
What are the marine zones?
- Photic (100-200m depth)
- Aphotic (depth where light doesn’t reach)
- Benthic (along the bottom)
- Neritic (shallows)
- Intertidal zone (shore)
- Oceanic (length past the shallows)
Describe the Hutchinsonian niche
- Describes fundamental characteristics of any species: the global maximum population growth rate (rmax); the niche optimum (the environment for which rmax is reached); and the niche width (the environmental range for which intrinsic population growth rates are positive
Difference between fundamental and realised niche
- Realised niche: set of environmental conditions where the species occurs
- Fundamental niche: set of environmental conditions that the species can tolerate
What is the optimal foraging theory and it’s equation?
- Animals choose the most energy-efficient prey
- P = E / (S+C)
where P = net energy gained, E = energy gained from consuming prey, S = energy required to search for prey, C = energy required to digest the prey
What are the assumptions of the mark-recapture method and the equation?
- No immigration or emigration
- All members mix randomly
- Marks remain between samples (don’t fall or rub off)
- IC / Pop. size = RM / CR
What are the assumptions of the geometric growth model and what is the equation?
- Basic form of future population estimation
- Nt = (λ^t)(N0)
If λ > 1, population _____
If λ < 1, population _____
increases
decreases
What are the assumptions of the logistic growth model and it’s equation?
- Closed population
- Changes in abundance are concentrated around a discrete time (breeding season)
- Per capita birth and death rates are independent of the environment or pop. size
- All individuals are treated equally (age, sex ignored)
- ΔN/Δt = rN(1 - (N/K))
Where N = pop density
r = intrinsic per capita rate of increase (=ln(λ))
K = carrying capacity
Describe the exponential continuous-time population growth model?
- Species produce offspring randomly
- Closed population
- Per capita birth and death rates are independent of the environment or pop. size
- All individuals are treated equally (age, sex ignored)
- The continuous-time model is Nt = N0 e^rt , where Nt is the population abundance in the future, N0 is the population abundance in the first year, e is the natural logarithm, r is the instantaneous per capita rate of population growth (r = (B - D)/N0), and t is time. Produces exponential growth
Describe the logistic continuous time model for population growth?
- includes a carrying capacity term
- dN/dT = N(rmax)((K-N)/K)
dN/dt is the change in population density over time, N is the population density, rmax is the intrinsic rate of increase, and K is the carrying capacity. - The (K − N)/K slows population growth as the population density approaches K.
- The population density levels off at the carrying capacity, produces a stable equilibrium.
Describe discrete time population growth?
- Assumes the population can overshoot the carrying capacity and then quickly return to that value.
- Nt+1 = Nt + Nt(rdis)((K-Nt)/K)
where Nt+t is the population density at the next time step, Nt is the current population density, rdis is the maximum per capita rate of population change, and K is the carrying capacity.
- If rdis < 1, the equation leads to _____ _____
- if 1 < r < 2, it leads to ____ _____
- if 2 < rdis < 2.57, it leads to ___ ___ ___
- if rdis > 2.57, it leads to ____ ____
- monotonic damping
- damped oscillations
- stable limit cycles
- chaotic dynamics
Describe negative-density dependent
- Intraspecific resource competition
- Pops have higher per capita growth rate when small
- Is known the be wrong because the less individuals in a population, the less fit it is
Describe the allele effect
- Contrast to negative-density dependence
- Populations at low numbers are affected by a positive relationship between population growth rate and density
- Low density makes it harder to find mates, fend off predators, environmental conditioning
Difference between Environmental and demographic stochasticity?
- Environmental stochasticity is the change in the average birth and death rates from one time period to the next because of random changes in environmental conditions
- Demographic stochasticity is when no change happens in the average birth and deaths from one period to the next, but individuals don’t follow averages. Just by chance, we could have a lower or higher number of survivors, births etc than the expected base average
When and why would you use age-stage pop. dynamics?
When a species has distinct life stages which each have unique rates of survival and fecundity.
What are the three types of survivorship curves?
- Type I: high early survival until a certain age, and then survival declines rapidly (e.g., humans, elephants, whales)
- Type II: constant survival throughout its lifetime (e.g., some seabirds and reptiles)
- Type III: very low initial survival during early stages until a certain age is reached, and then high survival till death (e.g., trees, amphibians, insects, marine invertebrates)
What are the assumptions of a metapopulation?
- all patches are equally accessible to dispersers, regardless of habitat barriers or distances between patches
- each habitat patch may either be unoccupied or occupied and at carrying capacity
- if a disperser arrives in an empty patch, it may found a new population, which then grows to carrying capacity;
- if it arrives in an occupied patch it has a negligible impact on the population dynamics of that patch
Describe the “flickering light” phenomenon seen in Levins metapopulation model
- All patches have an equal chance of being populated, as well as extinction and colonisation rates being constant
- Because of this the patches, from moment to moment will show newly colonised, newly extinct and declining populations
What is the equation for metapopulation prediction?
Δp/Δt = cp(1-p) - ep
where p = patches occupied
c = colonisation rate
e = extinction rate
Note:
- when c>e the metapopulation reaches an equilibrium where a constant proportion of patches are occupied
- when e>c eventually metapopulation goes extinct
Describe C3 photosynthesis
Activated electrons from sunlight provide energy to build sugars that contain energy-rich bonds. The sugars then head off to the rest of the plant to power the plants respiration, reproduction and assimilation. Water is used at the beginning when carbon dioxide is combined with RuBP to create two molecules of PGA which is the basic building block for glucose and other sugars. The essential enzyme for this conversion is not very good at its job. Sometimes CO2 gets too low or when temps are high RuBP tends to grab O2 instead of CO2 because it’s retarded, and that wastes time. This leads to photorespiration where O2 gets combined with sugars and slows down the energy capture rate as well as reduces photosynthetic efficiency
Describe C4 photosynthesis
Done when water levels are low, thus the emphasis is limiting the amount of water loss experienced from leaving the stomata open. In this process CO2 combines with a three-carbon compound called phosphoenolpyruvate (PEP). This combination ends with a four-carbon compound which heads off to the bundle sheath cells away from the stomata. Then within the sheaths the compounds break down again to feed CO2 through the Calvin Benson cycle to create the sugars. The CO2-rich environment in the interior bundle sheath cells reduces photorespiration, and the low concentration of CO2 in the mesophyll cells speeds up CO2 acquisition and leads to less time with open stomata (because gradient is stronger, so efficiency increases). There is a little loss of energy in the extra step, but water efficiency is much greater
Describe Crassulacean Acid Metabolism photosynthesis
Involves a temporal separation rather than a spatial separation between getting CO2 and making sugars. In this case the plants only open their stomata at night. CAM photosynthesizers combine CO2 and three-carbon compounds into four-carbon acids. During the day when the stomata are closed the acids are broken down into CO2 for the carbon-benson cycle and three-carbon compounds are recycled for tomorrow night’s CO2 collection.
What is the difference between interference and exploitation competition
- Interference competition occurs when one species directly interferes with the ability of its competitors to access a limited resource
- Exploitation competition occurs when one species reduces the availability of limiting resources to another species, simply by using it. Species compete indirectly through their mutual effects on the availability of a shared resource
Describe the principle of competitive exclusion
- When two species overlap substantially in their resource use,
even a slight advantage in acquiring the resource by individuals of one species will impose fitness costs
on individuals of other species that drive them to extinction.
When isoclines do not cross, it implies ____ _____results. Depending on which isocline is _____ the other, either species 1 or species 2, always drives the other to extinction
competitive exclusion
above
When isoclines cross it implies that competitive exclusion occurs, but which species wins depends on ____ ___ ____. Or if all arrows point to the point of intersection, where stable equilibrium occurs, then coexistence occurs but each species is ____ ____ ____ ____
where you start
below their carrying capacity
Describe the Ghost of Competition Past
Past competition may explain many current ecological patterns, but in most cases we will never know
Describe Resource Partitioning
Species use a limiting resource in a different way (e.g one uses the tree trunk for shelter, one uses the branches for a nest and one eats the insects living in the tree)
Describe Character Displacement
An adaptive shift in a population-level mean trait of a phenotype for a trait that is critical to resource acquisition and other competitive interactions
Faster resource consumption ____ carrying capacity
lowers
How can parasites affect population dynamics ?
- Parasites can reduce their hosts rates of survival, reproduction and population growths.This means they can regulate a hosts pops dynamics and drive host pops extinct, reducing their geographic range
What causes subsequent “waves” of infection during an epidemic?
- Transmission rates increase again after the previous wave (e.g due to relaxing physical distancing)
- Enough susceptible people remain in the population after previous waves or are newly introduced
What are the two ways to keep the density of susceptible individuals below the threshold
- Decreasing transmission rate (β) (aka “flattening the curve”) increases the threshold ST = m/β. This can, for example, be accomplished by increasing hygiene, physical distancing, or by quarantine measures. Increasing recovery rates (m), for example through better treatment, also increases the threshold ST = m/β.
- Increasing recovery rates
Describe the the life-lunch principle
the stakes are higher for the resource species in a consumer-resource encounter: it might lose its life, while the consumer might just lose out on a meal if unsuccessful
What are the three levels/types of defenses that animals have?
- Primary Defenses (prevent being found by the consumer)
- Secondary Defenses (deter consumers from attacking)
- Tertiary Defenses (escape or fight back when attacked)
What’re the assumptions of the Lokta-Volterra Predator-Prey Model for Stability
- closed populations
- no regulation of prey via density dependent factors:
negative (e.g., intraspecific competition) or positive (Allee effects) - The prey grow exponentially in the absence of predators
- Predators capture a constant fraction of the prey that they find regardless of how many prey they encounter
Describe bottom-up control ecosystems
- Control of the energy flow in a food web by organisms at the basic trophic level (autotrophs).The autotrophs act as gatekeepers to the upward flow of energy, thereby constraining the abundance of species at higher trophic levels.
- The effects of bottom-up control can often be seen by enriching the lowest trophic level and observing the effects on biomass across upper trophic levels.
Describe top-down control ecosystems
- Control of the energy flow in a food web by organisms at the upper trophic levels. By eating organisms at the lower trophic levels, the species at the upper trophic levels control the biomass and abundance of lower levels.
- The amount of nutrients present in lakes can determine the state of an aquatic body. Increasing limiting nutrients, such as phosphorus (P) and nitrogen (N), can result in massive algal blooms. Decomposition of these algae by bacteria depletes the dissolved oxygen in the water and can lead to hypoxia and high zooplankton & fish mortality
What are two methodologies that exist for determining a species’ diet?
- Direct observation was key in many classical studies
- Gut content and faecal analyses can provide more complete documentation of a species’ diet, as well as other information such as on the species’ parasites.
What are stable isotopes and how do they relate to ecology?
Stable isotopes are variants of chemical elements that have differing numbers of neutrons in the atomic nucleus that do not decay radioactively over time. Using a mass spectrometer, ecologists can measure the ratio of different isotopes in tissue samples. As stable isotopes are preserved through trophic transmission, these ratios can be used to determine an individual’s diet, days, weeks, or even months into the past depending on the tissue sample.
What does the measuring the carbon isotope ratio 13C:12C in tissue samples indicate?
The individuals carbon source (e.g food)
What does measuring the nitrogen isotope ratio 15N:14N in tissue samples indicate?
An individual’s trophic position
Note: 15N accumulates in higher trophic levels (~3.4 additional units of 15N per trophic level)
Describe foundation species
Species that have a large effect on community structure, function, and/or diversity that is proportional to their biomass and/or abundance
Describe keystone species
Species that have a disproportionately large effect on community structure, function, and/or diversity, relative to their own biomass and/or abundance
What three points make up the United Nations Environment Programme’s Convention on Biological Diversity’s definition of “Species Richness?”
- The total number of species on Earth (global species richness)
- The evolutionary diversity represented by these species
- The diverse communities and ecosystems that these species build
What holds more species; a heterogenous or homogenous habitat?
a heterogenous habitat. Heterogenous implies difference among species, homogenous implies it is mostly one or few species that make up the habitat
What are three ways to describe species richness across different habitats?
- y-diversity:
* Species richness of an
entire region that is
made up of small
habitats. y = avg # of
spec - a-diversity:
* a = avg # of spec found
in the small habitats of a
region - B-diversity:
* A measure of
heterogeneity of
community compositions
among localities
* B = y/a
What are five challenges for estimating?
- A historical reliance on physical and morphological characteristics often led to morphs of a single species being described as separate species.
- A historical reliance on physical and morphological characteristics often led to individuals of different species being classified as morphs of the same species.
- Biases exist with respect to which species and/or environment are studied
- Many species are hard to find and researchers are limited by logistic, time, and funding constraints.
- Many species are going extinct before they are described.
In most communities, ____ species account for most individuals; ____ species can be considered rare
a few, most
How do we know when our sampling efforts have captured a community’s species richness and composition adequately?
Species accumulation curves are initially steep but then level off once most species have been identified (the more you sample, the less likely it is that you see something new). Levelling off of the species accumulation curve can indicate adequate representation of the community in the samples
Describe species-area relationships:
The number of species that are found will increase with the area that is sampled: steeply first, and then more slowly as the probability increases that sampled species have already been observed in previous areas
S= cA^z
log S = log c + z log A
S = # of species in a given area
A = Area
C = avg. # of spec per unit area
z = slope of log-log transformed species-are relationship
Two communities may have the same ____ ____ (the number of species in a community), but differ in their composition. ____ ____ describes how evenly individuals are spread among species by considering the relative abundances of each species compared to one another.
species richness
Species evenness
Define the Shannon-Weiner Diversity Index
Determines the proportional abundance of each species in a community. The population of each species is compared to the total. This can then rank the ratios from highest to lowest to determine whether there is large variability (species richness) and even proportionality (species evenness)
What is the Shannon-Weiner Diversity Index equation?
What is a downside of the Shannon-Wiener Diversity Index?
Two communities could have identical species richness and evenness but completely different species compositions and functions. It matters which species are present in a community; simply tallying up species richness / evenness might miss key details
The ____ of a rank abundance curve indicates species richness and its ____ measures evenness
length
steepness
How would you measure phylogenetic diversity?
- By adding up all branch lengths within a phylogeny to create a single number that can be compared across locations and through time.
A set of species that are evolutionarily very different from one another will have a ____ PD score that a set of closely related species
higher
What are Functional traits?
Characteristics of species that describe their ecological roles in a community.
What do Functional diversity dendrograms do?
- Graphically depict the relationships among a set of species in terms of their functional traits
- Adding up the length of all branches produces a metric that can be regarded as an estimate of a community’s functional diversity (FD), as measured through functional richness (the number of traits present in a community) and functional evenness (the proportion of individuals in each functional group)
What are the three hypotheses that address the latitudinal gradient in diversity?
- Hypothesis 1: Large, thermally stable areas result in larger population sizes and larger population ranges, which decreases each species’ extinction risk and increases the rates of speciation
- Hypothesis 2: Species diversity is larger in the tropics than in higher-latitude areas because the tropics have been climatically stable for longer periods of time, thus giving species more time to evolve.
- Hypothesis 3: Species diversity is larger in terrestrial tropical systems than in temperate ones, because terrestrial productivity is generally highest in the tropics: high productivity promotes higher carrying capacities and thus larger population sizes and decreased extinctions risks.
Describe The Effects of Island Size and Distance to the Mainland on the Island’s Species Richness:
- Bigger island = more species richness
- Closer island is to mainland = more species richness
- Rate of colonization
decreases when island
species richness is high - Rate of extinction increases with
higher species richness
Define primary succession
- Succession that begins in/on substrates that contain no organisms and no organic material.
- Tends to be slow, as the first colonists must arrive from elsewhere, and it is only through the actions of these species that the environment becomes suitable for the establishment of species in later series
Define secondary succession
Occurs following a disturbance where some, but not all, organisms have been destroyed. E.g forest fires
What are the differences between r and k selected species?
R-Selected:
- Generally small, fast-growing organisms that live in unstable environments and produce a large number of offspring
- Early colonisers
K-selected:
- Typically large, slow-growing organisms that live in stable environments and produce only a few offspring that they can give a lot of care to
- Later colonisers
What takes longer, primary or secondary succession?
Primary
What are the three Connell & Slater succession models?
- Early succession: Facilitation likely most important, especially when physical conditions are stressful
- Mid succession: Mixture of positive and negative interactions
- Late succession: Bigger, long-lived species; competition most important
What are community assembly rules?
- How the timing of species arrival or the initial suite of colonising species can determine the species composition of the community. - - At least some such rules must exist (e.g., obligate parasites cannot establish without their host; specialist predators cannot establish without their prey; obligate mutualists cannot establish without their mutualistic partner)
What did James Drake’s experiments on microcosms show?
- Widely differing community compositions can be achieved by solely altering the sequence of colonisation
- Variability among replicates was low, suggesting repeatable mechanisms at play
- Some sequences can lead to community compositions that prevent any further colonisation
Define restoration ecology
Aims to manage, via “large-scale experiments”, highly degraded or newly established sites by providing conditions that make sites physiologically tolerable for a diverse array of species to accelerate succession towards a desired endpoint community,
Describe the intermediate disturbance hypothesis
Suggests that species diversity will be greatest at intermediate levels of disturbance:
- A stable environment leads to competitive exclusion by dominant species for many other species and limits diversity (mostly K-selected species will persist)
- High mortality through disturbance excludes many species and limits diversity (mostly r selected species will persist)
- Note: Not very accurate
Describe the facilitation model of succession
Early species modify the environment in ways that benefit later species. The sequence of species facilitation leads to a climax community.
Define climax community
The final stage of ecological succession attainable by a plant community. As plant succession occurs, so does animal succession. As pioneer species establish that life can exist in the area, more advanced plants and animals will move in and become established as well
Describe the tolerance model of succession
Early species modify the environment in ways that neither benefit nor inhibit future species.
Describe the inhibition model of succession
Early species modify the environment in ways that inhibit future species. Requires some form of disturbance for succession to continue
We refer to systems as ____ if they have two stable equilibria to which the system can be attracted. ____ occurs when a larger perturbation is needed to shift a system from equilibrium A to B, than it is to shift from equilibrium B to A
bistable
hysteresis
What are some negative ecological impacts of climate change?
- Species with short generation times may be able to adapt to a changing climate, but for species with long generation times, environmental changes often outpace their ability to adapt. New “hybridization zones” may also arise due to the altered ranges of species, leading potentially to the rise of new species.
- Climate change is shifting seasonal patterns around the globe, driving changes in phenology (the timing of periodic biological phenomena that are correlated with cyclic or seasonal events). If the timing of events shifts in different manners for interacting species, phenological mismatches may occur.
What is the dilution effect?
Suggests that higher biodiversity leads to reduced disease. This effect may have large consequences for human health if tropical, mosquito-borne diseases were to establish in temperate regions.
How does land use impact ecology?
- By far the biggest threats to ecosystems
- Habitat degradation: Changes that reduce the quality of a habitat.
- Habitat loss: When a natural habitat becomes incapable of supporting its native species
- Habitat fragmentation: When continuous habitat is broken up into smaller pieces. Aside from leading to smaller habitats, habitat fragmentation tends to increase the number of contact edges between habitat and non-habitat, leading to an increased vulnerability to edge effects
What are the negative impacts of overexploitation on ecology?
- Unsustainable exploitation can lead to abundance declines or extinctions of the resource species
- Exploitation (~harvesting): the destructive use of animals, plants, and their products for various consumptive (e.g., food, medicine) and non-consumptive (e.g. trophy hunting) purposes. Nt+1 = r Nt - e Nt ; e < r
- Overexploitation (~overharvesting): harvesting wild organisms at rates that are faster than the rates at which they can recover. Nt+1 = r Nt - e Nt ; e > r
Describe invasive species impact on ecology
- Managers try to control invasive species by chemical, biological, and physical means. A combination of approaches often works best.
- Controlling an invasive species early maximises the chances of success and minimises the costs: due to low initial densities and localised populations, Allee effects, demographic stochasticity, environmental stochasticity, and other mechanisms, increase the chances of eradication
Define the greenhouse effect
Warming of the earth by atmospheric absorption and re-radiation of infrared radiation emitted by earth’s surface. This effect is due to greenhouse gases in atmosphere, primarily water vapor (H2O), carbon dioxide (CO2), methane (CH4) and nitrous oxide
In hierarchical sampling designs, if there are four sampling sites, how many quadrats will there be in total?
1 sample site = 3 fields
1 field = 3 transect lines
1 transect line = 5 quadrats
Thus
4 sample sites = 12 fields = 36 transect lines = 180 quadrats
______ disturbances are naturally occurring
disturbances including fire, rainfall variability, and herbivory. Grasslands are adapted and to
some degree depended on these disturbances since they are natural phenomena.
endogenous
_____ disturbances are usually anthropogenic in origin and
disrupt the soil surface, this includes afforestation, agriculture, and urbanisation
exogenous
Match the following components of Intermediate disturbance
hypothesis with their associated phenomena:
- Mild Disturbances
- Intermediate Disturbances
- Frequent Disturbances
A. Keeps strong
competitors from excluding
weak competitors but not
much disruption for species
that need a stable
environment
B. Competitive Exclusion
C. Exclude all but the species
adapted to disturbance
I. K selected persist
II. R selected persist
III. Both persis
- B I
- A III
- C II
What’s the difference between abiotic and biotic disturbances?
Biotic:
- Living caused disturbances (grazing, disease)
Abiotic:
- Non-living caused disturbances (weather, fires)
What is the difference between natural and unnatural disturbances?
Natural:
- Occur naturally (weather, herbivory)
Unnatural:
- Occur unnaturally (anthropogenically)
Lokta volterra equation for spec 2 on 1
Predator detection equation
A predator moving at velocity v [units: km/h], and with a max. detection distance d [units: km], covers 2/ km2 /h.
If prey are distributed randomly with density N [number of prey per km2 ] the predator will encounter 2/N prey per hour.
Assuming that a successful attack occurs in p per cent of all encounters, each predator takes p2dvN prey per hour
Since there are P predators, the total loss rate of prey becomes (p2dvN)*P
Lokta volterra equation with allee
What are the predator-prey zero growth isocline equations
