Other questions Flashcards
What are indirect effects in a food web?
The impact of one organism or species on another that is mediated or transmitted by a third
What is a species interaction?
The outcome of two individuals coming in to contact
What is interaction strength?
The degree to which a species location in a food web structure is dependent on a given interaction with another species.
Or, the strength of an interaction is the relative change caused by severing that interaction.
What is a classic example of indirect effects in a food web?
The removal of otters from the kelp forest community lead to a loss of kelp through an overabundance of sea urchins.
How has research on trophic cascades advanced our knowledge of community ecology?
Trophic cascades help model the combined direct and indirect effects of a community, as well as the transition between community states.
What is top down forcing? Give a strong piece of evidence for it.
Predators shape community structure. E.g. otters
What is bottom up forcing? Give a strong piece of evidence for it.
Resources can limit the abundances of species at higher trophic levels. E.g. seagrasses
Imagine you have a long time series of monitoring data from the same transect on primary producer, herbivore, and predator abundance. Explain how you might infer if the system was under top-down or bottom-up control.
You could track the relative abundances of each and look for time lags in response to stochastic events that affect the primary producers and predators.
What is the functional response in consumer-prey relationships?
Can be Type I, II or III.
Type I: Linear density of prey: prey consumed
Type II: Decelerating intake rate, which follows from the assumption that the consumer is limited by its capacity to process food (rectangular hyperbola)
Type III: Accelerating intake rate
Why is ocean acidification worse in colder waters?
CO2 is more soluble in cold water,
Describe the Lotka Volterra model.
A pair of first-order, nonlinear, differential equations frequently used to describe the dynamics of biological systems in which two species interact, one as a predator and the other as prey.
What is the difference between a fundamental and realized niche?
Fundamental niches represent all the environmental conditions where a species is able to live, and the realized niche is where the species actually lives. Other names for these niches are precompetitive and postcompetitive, respectively.
Describe the three survivorship curves.
Type I or convex curves are characterized by high age-specific survival probability in early and middle life, followed by a rapid decline in survival in later life. They are typical of species that produce few offspring but care for them well, including humans and many other large mammals.
Type II or diagonal curves are an intermediate between Types I and III, where roughly constant mortality rate/survival probability is experienced regardless of age. Some birds and some lizards follow this pattern.
Type III or concave curves have the greatest mortality (lowest age-specific survival) early in life, with relatively low rates of death (high probability of survival) for those surviving this bottleneck. This type of curve is characteristic of species that produce a large number of offspring (see r/K selection theory). This includes most marine invertebrates. For example, oysters produce millions of eggs, but most larvae die from predation or other causes; those that survive long enough to produce a hard shell live relatively long.
What is life table analysis?
A table which shows, for each age, what the probability is that a person of that age will die before his or her next birthday.
What is the source-sink model?
In this model, organisms occupy two patches of habitat. One patch, the source, is a high quality habitat that on average allows the population to increase. The second patch, the sink, is very low quality habitat that, on its own, would not be able to support a population. However, if the excess of individuals produced in the source frequently moves to the sink, the sink population can persist indefinitely.
What is Leibig’s law of the minimum?
Growth is dictated not by total resources available, but by the scarcest resource (limiting factor)
What is an optimal foraging or migration model?
Method of obtaining food or migrating that maximizes the benefit for energy/time expendature
What are the costs and benefits of social groups?
Benefits: foraging efficiency, reduced predation, access to mates, help from kin
Costs: competition for food, increased disease transmission, attracting predators
How does behavioral ecology fit into natural selection?
Survival and fitness depends on behaviors
Shelford’s Law of Tolerance
geographical distribution of a species is controlled by the environmental factor for which the organism has the narrowest range of tolerance.
What kind of experiments help discern a species range?
Transplant
What two forms do competition take?
Direct/Indirect or Resource/Interference
Direct if trying to use a common resource in short supply
Indirect if one organism seeking a resource is harmed by another in the process, even if not in short supply.
What are the major abiotic limitations to the distribution of plants and animals on land?
Temperature and moisture
What is Rapoport’s Rule?
Polar species tend to have larger ranges
What is generally true of the relationship between distribution and abundance?
They are positively correlated - widespread species also tend to be more abundant. Hanski’s rule.
When modeling populations, its important to distinguish between ______ and _______ fertility/longevity
realized and potential.
What is the competitive exclusion principle?
complete competitors cannot coexist
What is a functional response?
The change in predator consumption in relation to the density of prey species
What is a limiting factor in population regulation? What is a regulating factor in population regulation?
If a change in the factor produces a change in average or equilibrium density. E.g. a disease is a limiting factor in deer if more deer are present when disease is absent
If the percentage mortality caused by the factor increases with population density. E.g. disease is a regulating factor if it causes a higher fraction of losses as deer density increases
What is the allee effect?
small populations can suffer reduced population growth> produces instabilities that can lead to local extinctions.
mechanisms: not enough mates
Losses due to harvesting of an organism must be compensated by three things…
increased growth, increased reproduction, decreased natural mortality
What do yield models assume and when does this break down?
Equilibrium, they fail when there are changes in conditions, weather, predators, disease, etc.
What are three stochastic forms of variation that contribute to extinction risk?
demographic, genetic, environmental
What effects does reduced connectivity have on population dynamics?
Affects rates of dispersal and immigration
What is the neutral theory of biodiversity? What are its assumptions?
The differences between members of an ecological community of trophically similar species are “neutral”, or irrelevant to their success. This implies that biodiversity arises at random, as each species follows a random walk.
: that species are ecologically equivalent
: communities are saturated with species and in equilibrium
What is the gradient of diversity? What are some explanatory mechanisms?
The increase in species richness or biodiversity that occurs from the poles to the tropics.
A combination of energy/climate and area processes likely contribute to the latitudinal species gradient.
What are six factors that affect biodiversity?
: evolutionary speed : rapid evolution of new spp
: productivity : richness limited by production partitioning among spp
: disturbance : moderate disturbance slows competitive exclusion
: geographic area : larger/more complex areas make more niches
: interspecific interactions : competition affects niche partitioning and predations slows competitive exclusion
: ambient energy : fewer species can tolerate unfavorable conditions
What is another core community structure pattern?
That most communities have few common species and many rare ones.
What is a keystone species
species that occupies a role of critical importance to a community
What is a dominant species?
One that controls the occurrence of other species
What is fishing down the food web?
Fisheries being depleted of apex predators so catches become increasingly dominated by lower trophic level species
What is the difference between local and global stability?
Local refers to system returning after small disturbance, global refers to system returning after large disturbance.
What is the green world hypothesis?
Hairston, Smith and Slobodkin argued that predators reduce the abundance of herbivores, allowing plants to flourish. The green world hypothesis is credited with bringing attention to the role of top-down forces (e.g. predation) and indirect effects in shaping ecological communities.
What is a trophic cascade?
Impacts flow down the food chain as a series of positive and negative impacts on successive trophic levels
What is island biogeography theory?
Predict species richness based on island size (area) and isolation (distance). This theory does not try to predict species composition or abundance. It also considers species richness to be in dynamic equilibrium between immigration and extinction. Extinction and colonization rates are affected by island size and distance. Larger islands have more species and closer islands have more species. Species richness depends on size and distance. The theory also explains that more species means lower colonization rates and higher extinction rates.
What is an example of a system with multiple stable states?
Coral reefs in the Caribbean can phase shift to algal dominance, both are stable.
What is the species-area curve?
Shows the relationship between species and area, often used to refer to biodiversity increase with island size.
What is the primary limiting factor on productivity in marine environments?
Nutrients, nitrogen then phosphorous.
What is the metabolic theory of ecology?
Posits that the metabolic rate of organisms is the fundamental biological rate that governs most observed patterns in ecology. In MTE, this relationship is considered to be the single constraint that defines biological processes at all levels of organization (from individual up to ecosystem level), and is a macroecological theory that aims to be universal in scope and application.
What does metabolic rate scale to the power of? What is this called?
3/4, a power law
What are the implications of MTE on population growth?
The optimal population growth rate for a species is therefore thought to be determined by the allometric constraints outlined by the MTE, rather than strictly as a life history trait that is selected for based on environmental conditions.
What are the implications of MTE on ecosystems?
The average production to biomass ratio of organisms is higher in small organisms than large ones. This relationship is further regulated by temperature, and the rate of production increases with temperature. As production consistently scales with body mass, MTE provides a framework to assess the relative importance of organismal size, temperature, functional traits, soil and climate on variation in rates of production within and across ecosystems.
What are ecosystem services of coral reefs?
coastal protection, fisheries nurseries, aesthetic beauty
What are weak effects?
When an interaction is not critical to the survival or fitness of another species, but they do interact.
More technical: When the removal or addition of a species
failed to cause a statistically discernible mean change in the abundance of a target species
Communities are structured by primarily weak interactions and some strong ones but weak effects, counterintuitively play a critical role in maintaining food web structure to their role in stabilizing.
Describe what would you might believe would happen to species interactions (interaction strengths) if nutrients and light weren’t limited in an environment and the temperature increased. In and out of an equilibrium?
What happens to the carrying capacity in each situation
.
Are positive interaction predictable features of natural communities?
We expect to see more positive species interactions in high stress environments that have higher consumer pressures, and less where the physical environment is benign and consumer pressure is less.
There are probably many exceptions to this.
