Ecology Test 2
|population||a group of potentially interbreeding organisms at the same time and place, that share a common gene pool.|
|population growth rate||change in number over time, as a function of (birth + immigration) - (death + emigration).|
|Population structures|| -age class structure|
-spatial structure ( pattern of how individuals are distributed through the range)
|Population ecology attributes (6)|| -population|
|The Niche Concept||organisms will only live in ecologically suitable habitats|
|fundamental niche||describes the abiotic conditions organisms can tolerate|
|realized niche||includes biotic effects, like distribution of food, competitors, and predators|
|limiting variable||something that shifts tolerance to intolerance|
|Regular dispersion||variance is less than the mean, can be zero if equally dispersed. Usually caused by intraspecific competition, such as allelopathy or territoriality.|
|Clumped dispersion||variance is greater than the mean, usually caused by sociality or common response to clumped resources.|
|Random dispersion||Variance ='s the mean. Rather unusual, just because clumped resources and competition are so common. But previously clumped or regular distributions can degrade to random over time, such as when seedlings (clumped) grow up and compete (regular) and then die of other causes.|
|metapopulation model|| -equal habitat quality and adapted local populations. |
This model describes the dynamics among sub-populations connected by migration. Populations inhibit equivalent habitats, and the dynamics are governed by population sizes (which determine the likelihood of extinction and the number of migrants leaving), and proximity to other habitats (which determines the probability of donating and receiving other migrants).
|source-sink model||-variable quality habitats and migration between.|
This model adds one piece of complexity, recognizing that the quality of habitats may vary. So, in accordance with the 'habitat selection' model, populations in high quality habitats will typically be large, and will typically be donors ("sources") of migrants.. whereas populations in marginal habitats will be smaller and will be recipients ("sinks") of migrants. Now, migration rates not only depend on distance but also on relative habitat quality and population size.
|landscape model||variable quality habitats, migration dependent on connectedness. |
-This model adds another layer of complexity, and considers the effects that variation in the matrix can have on both patch quality and migration. The matrix can influence patch quality by being a source of other species that can visit the matrix- either by providing food (like seeds blown into the patch from the outside) or competitors or predators. Also, the matrix can affect migration rates between patches, because it may be a tolerable "corridor" or truly an impermeable barrier. There is a whole disciple of "landscape ecology" that looks at the effects of the distribution and connectedness of patches and habitat types on populations and communities.
|Macroecology||deals with large scale patterns in ecology- such as relationships between body size and species ranges. It as a fairly new subdiscipline (Brown 1984) that takes a very top-down approach- looking for important biological insights by looking at relationships across large taxonomic and geographical scales.|
|Species with high local abundances have large ranges||There is considerable variation in this relationship (it only explains 13% of the variance in range size) but is still strongly significant. Brown explained it this way: generalist species that exploit a wide range of resources can reach high abundances in the middle of their range (there is more food), and should be able to spread out over a greater range of habitats (where they can eat this or that).|
|Large organisms have lower population sizes than small organisms.||Obviously, there are some energetic constraints here. However, Brown found an interesting relationship: biologically similar organisms (mammals, for instance) that differ in size show a fairly constant amount of food used/ unit area- even though metabolic efficiencies increase with body size. This is the energy equivalence rule.|
|energy equivalence rule||biologically similar organisms (mammals, for instance) that differ in size show a fairly constant amount of food used/ unit area- even though metabolic efficiencies increase with body size|
|The shapes of ranges||-in the US, abundant species have ranges running E-W; rare species have ranges running N-S. |
-Brown hypothesized that species wit large ranges were generalists, able to adapt to a variety of habitats. Rare species were specialists, with narrower niche species limited to a particular elevation, for instance.
-Brown tested this idea by looking at Europe, where it was the opposite.
|static life table||measure parameters over different age classes for one time period|
|dynamic ("cohort") life table||follow a group through their life|
|stable age class distribution||the proportional representation of each age class equilibrates, and each age class grows at the same rate.|
|population's growth potential||a function of the population's survivorship and fecundity schedules, and is calculated as Net Reproductive Rate (Ro) and intrinsic rate of increase (r)|
|Malthus||all populations have the capacity to expand exponentially. Even those with a slow growth rate because of delayed reproduction and low fecundity, like large mammals, can increase to huge populations rapidly if unrestricted.|
|selection|| "differential reproductive success"|
-organisms (or subpopulations) that reproduce the most will dominate the population over time
-selection will favor a particular survivorship and fecundity schedule in a given environment
|carrying capacity|| equilibrial density where birth rate = death rate. |
-dependent on the environment
|Logistic Growth Curve equation||dN/dt=rN(K-N)/K|
-when pop. is small, (K-N)/K goes to one and the growth rate approximates the exponential max of rN.
-when the population is large and almost as large as K, then (K-N)/K goes to zero, and the population does not grow... it has reached equilibrium where b=d.
-when pop. is larger than carrying capacity, then (K-N)/K becomes negative and the population declines in size
|Discrete growth||-roughly speaking, the change in population size will be a function of its intrinsic rate of growth (r) and the size of the current population relative to the carrying capacity|
|Continuous growth||-should b able to match reproduction to resources more closely, but there are "time lags" due to the biological processes of metabolism and development.|
If reproductive potential and time lag are low, then the potential to overshoot is small.
As either or both of those increase, then the magnitude of overshoot increase. When the product Rt>1.6, there are huge swings in the population size.
|predation||capture, killing, and consumption or an individual prey item (even "seed predation")|
|parasitism||consumption of a portion of the host by internal or attached parasite- usually non-lethal in itself|
|pasasitiodism||consumption and death of host by internal parasite|
|herbivory||consumption of plant tissue, either killing the plant (predation) or not (parasitism). Grazing removes tissue from herbs, browsing removes tissue from woody vegetation (even leaves from trees = browsing)|
|Species interactions (5)|| -mutualism (+,+)|
-commensal (+, neutral)
-consumer (+, -)
-amensal (-, neutral)
|Responses to consumer-resource interaction (3)|| -structural/morphological|
|types of competition (2)|| -exploitative/'scramble'- organisms remove what they can, and neither may get enough|
-territorial/'contest'- competition for access to the resource, with 'winner take all'
|Responses to competition (2)|| -competitive exclusion (one species wins)|
-coexistence by resource partitioning
|Types of mutualisms (3)|| -trophic: involve species with complementary feeding relationships and they share food|
-defensive: one species provides defense to another, in exchange for some service or food
-dispersive: one species disperses pollen or fruit in exchange for food
|time lags||time lags between birth and reproduction in both populations. So, a prey population experiencing heavy mortality from predators will continue to decline even after the predators have declined, because many of the prey individuals are pre-reproductives and must mature before they can breed.|
|Competition||consumers using the same resource can reduce the availability of that resource to the point where population growth becomes limited- affecting either mortality or birth rate.|
|competitive exclusion principle||two species cannot coexist if their requirements are the same (same niche)- coined by Gause in the 30's.|
|a- "conversion term"||per capita effect of N2 individuals in terms of N1 individuals|
|Tilman models||competition by exploitation of resources|
-species in single-species treatments are monitored for the rate at which they reduce mineral nutrients, and the amount of nutrients they need to sustain a population growth (isoclines).
-then, based on a combined analysis of two species' isoclines, we should be able to predict the outcome of competitive interactions based on the ratio of resources in the environment, the rates at which the species consume these resources, and the minimum required amounts that each species needs for population growth
|Problems with Lotka-Volterra Models|| -not totally predictive in the case of two species; you have to do the competition experiment to define the a's under one condition. |
-The nature of the competitive interaction is undefined... what are they competing for?
|contest (or interference) competition||is for access to the resource, as in intrasexual competition among one sex for access to members of the opposite sex, or in territoriality or allelopathy|
|scramble (or exploitative) competition||direct competition for the resource, in which whoever gets the resource reduces the amount available to others by just that amount. Feeding frenzies are a nice example.|
|outcomes of competition||-negative effects: decrease in birth rate, growth rate, survivorship, and population size.|
-possible competitive exclusion of one species- and thus a restriction in its spatial/ temporal range
-resource partitioning- a change in the range of resources used by one or both species
-adaptation over time to the presence of a competitor
|character displacement||morphological change initiated by competition|
|Dynamics of mutualisms (4)|| -fitness benefit to both populations|
-diffuse (many partners) or species specific (one partner)
-faculktative (not necessary) or obligate (necessary)
-strength of any feedback loop depends on the degree of "obligateness"
|Gaia hypothesis||life has constructed an environment that is suitable for life- through feedbacks in the hydro- litho- and atmospheres.|
|Types of mutualisms (3)|| -trophic|
|Trophic mutualisms and examples|| -help one another get food|
ex. 'gut endosymbionts, plants and N-fixing bacteria, plants and fungi, algae and fungi, mixed foraging flocks,
|Defensive mutualisms and examples|| -trade protection for food|
Animals and Food sources
-leaf-cutter ants and their fungal gardens
-ants and aphids
|Dispersive Mutualisms and examples|| -trade food for transport|
ex. pollinations (bees, wasps, ants, butterflies, birds, bats, etc.)
seed dispersal: animals eat the seeds, digest the fruit, and pass through the gut or are regurgitated
|coevolution||-when species are involved in the 'evolutionary race dance' with another species, evolving in response to one another|
|types of coevolution in consumer-resource relationships|| -capture and evasion|
|batesian mimicry||palatable mimic mocks an unpalatable model|
|mullerian mimicry||multiple unpalatable species converge on one recognizable morphology, in a sense of mimicking each other. This is reinforced because the predators only need to learn one, and they then avoid all of these equally unpalatable species|
|stable class distribution||the proportional representation of each age class equilibrates, and each age class grows at the same rate|
|Prey Population Growth||rate of change = intrinsic growth rate - death by predation.|
dV/dt = rV - cVP
cVP = number dying by predation, which is a function of the encounter rate, which depends on the population sizes of both species (V)(P), and the 'functional response' or 'capture efficiency' ... what fraction of those encounters end in the death of the prey.
|Predator Population Growth|| rate of change = birth rate (~ food supply) - death rate|
dP= a(cVP) - dP
a = metabolic conversion rate of food to offspring, and cVP = number of prey caught.
|Type II Functional Response||in which the percentage of prey taken declines as prey population increases. This could be explained by satiation (predators are full and so don't kill prey at the same rate), or by predators becoming limited by handling time - predators simply cannot capture and kill prey any faster, regardless of how many more prey there are. Both of these will cause the predation rate to decline, and the number of prey captured to equilibrate, as prey population size increases.|
|Type III functional response||where there would be low efficiency at low prey densities... maybe because the predator fails to develop a search image, doesn't encounter the prey often enough to know it is food, or does not encounter the prey often enough to develop an efficient handling strategy (learning). Or, when one prey is at low density, a predator may switch to another, more abundant prey.|
|Maximum Sustainable Yield||The maximum number of prey items that can be removed without causing a decline in the growth rate of the population|