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Biology Exam 4
Terms in this set (96)
Individuals of the same species living in the same place at a given time
two reasons for population growth
birth or emigration
two reasons for population shrinkage
death or dispersal
number of individuals per unit area or volume
two basic population models and the distinction between them, also the important variables in both equations
exponential and logistical
the variable "k"
called carrying capacity, characteristic of the logistical population model, in which the population levels out at carrying capacity: the maximum number of individuals in a population that an area can sustain over a long period of time. function of how the organism uses the environment and the resources of the environment. those can change over time and so can the carrying capacity (humans have increased carrying capacity of earth to sustain our population through technology and new ways of exploiting new resources)
metapopulation and example
population of local populations that are born and die. local populations called habitat patches. connected through dispersal corridors. bay cherkerspot butterfly caterpillars feed on two types of plants that only grow on serpentine rock, so subpopulations are restricted to habitat patches based on the presence of serpentine rock.
models use emigration/colonization rates and extinction rates of local population patches to predict the persistence of the overall metapopulation
what is one way to cause extinction of a metapopulation?
cut off dispersal corridors
habitat patches that depend on colonization from other patches or populations
spatial structure of individuals in a local population. typically takes one of three forms (clumped, regular and random)
clumped dispersion results from? also, example from class
social structure of a population and/or habitat patches of varying quality (orcas)
random dispersion results from? also, example from class
territoriality and/or competition (seabirds)
regular dispersion results from? examples from class
random things like wind, currents, etc.
dandelions in a field randomly dispersed because their seeds are dispersed in the wind
planktonic larval dispersal in the ocean.
demography and example from class
quantitative study of determinants of population characteristics such as birth rates, death rates, movement, etc. as they depend on individual characteristics. complete census of an elephant population in a ugandan national park done. looked at distribution of ages in 1970 and then again in 2000.
in colloquial terms, what can demography tell us?
where a population is headed based on a characteristic like age or sex
What is a life table and why might you look at one?
life tables catalog rates of survivorship and mortality in cohorts of populations. used to keep track of demographic events and determine the rate at which these events occur. can be used to identify principal mortality factors at particular life stages to predict future population trends, and to develop strategies for managing populations of species of commercial or ecological value.
number of offspring per female
what determines fecundity? example
individual characteristics like age but also environmental factors. for instance, cactus ground finches on one island in the galapagos had zero fecundity for the two years following a drought.
demographic population model, uses and example
using some kind of population model coupled with demographic information to forecast population size/growth. used in the management of populations of interest (ecological or economical concern)
cod and haddock - shows the haddock population crashing over time and then in the 1990's moratoriums were put in place so their population started to increase again. the cod population crashed nearer to the beginning and continued to crash because fishing restrictions weren't put into place.
why do population outbreaks and crashes not happen very often?
because of density dependent growth, which allows populations to stay at some sort of equilibrium.
density-dependent growth factors
typically negative. negatively affect population growth as density increases. usually biotic factors like competition for resources, resources available, predation, disease)
density-independent growth factors
usually abiotic (like weather, and other things that don't affect the density of a population
optimal foraging theory
fitness depends on costs of pursuing, subduing, and handling prey against energetic and nutritional return from consuming it
density-dependent foraging behavior
predator efficiency tends to increase with density of prey available but it levels out because of constraints called handling time
time it takes for predator to capture, kill, eat and digest once prey has been spotted
learning that gets reinforced that helps predator detect prey
- convergence in appearance of two or more unpalatable species
three types of predator traits
behavioral, chemical, physical
The process of removing a chemical from the environment and sequestering it in an organic or physical structure
mimicry in which an edible animal is protected by its resemblance to a noxious one that is avoided by predators
describe why climatic temperature on Earth's surface varies with latitude
the angle at which sunlight strikes the earth's surface varies such that intensity of solar energy is highest at low latitudes and lowest at high latitudes. average climatic temperature reflects this latitudinal pattern.
at very high latitudes, biomes on earth can be classified as
the respsective responses of organisms to weather and climate are typically
behavioral and evolutionary
explain a key difference between the exponential and logistic model of population growth
the logistic model includes negatively density-dependent growht factors while the exponential model is free from this constraint. in the logistic model, the population grows exponentially at first, then its growth rate declines until it reaches zero (stable population size) at the carrying capacity
two key parameters in the metapopulation model and what the model predicts
1) rate of colonization of new habitat patches and 2) rate of extinction of local populations. the model predicts the probability of persistence of the metapopulation.
why is negatively density-dependent population growth so central to population ecology?
negatively density dependent population growth is what keeps population sizes within sustainable limits. except for unusual conditions, populations fluctuate around some equilibrium size due to negatively density dependent population growth
distinction between interference and exploitive interspecific competition
interference competition refers to direct interactions (physical or chemical) between competitors that limit access to resources that are being competed for (grizzly bear physically tries to chase off wolves or wolves might successfully defend their kill by chasing off the bear, whereas in exploitive competition indirect interactions between species lead to a depletion of available resources used by the competitors (wolves preemptively took care of that particular food source and grizzly bears never even encountered it)
character displacement and example
evolutionary divergence of traits used to exploit a resource (when species are competing with one another, the more strongly they're competing with each other, the worse the effects for them). traits to reduce the amount of competition. ex: character displacement in wing morphology of the cactus finch. cactus finch occurs on some galapagos islands. carpenter bees present on 5/7 of these islands. both the finches and bees feed on the cactus flower nectar (major limiting resource). on islands with bees, cactus finch has evolved shorter wings so they can more efficiently get nectar from these flowers. where bees are present, average wingspan of finch is longer so that they can more easily take advantage of other resources as well.
describe the role of abiotic effects and interspecific communication in the habitat partitioning of the rock barnacle and poll's stellate barnacle
desiccation and interspecific competition jointly cause the habitat partitioning (or intertidal zonation) of these species. the rock barnacle inhabits a lower intertidal zone than the stellate barnacle because the rock barnacle cannot tolerate the desiccation of the upper zone. the stellate barnacle inhabits a higher intertidal zone because it is more tolerant of desiccation, and restricted to that habitat zone from the competitive dominance of the rock barnacle. the stellate barnacle can persist in the lower zone if it does not compete with the rock barnacle. (interference competition because there's a direct interaction as one species is overgrowing the other one -- and it's limiting access to resources for the stellate barnacles)
warning potential predators of toxicity (coloration)
types of crypsis
chemical, visual, acoustic
organisms living in a particular area interacting with each other and the physical environment (a little bit broader than ecological community because its looking at interactions with the abiotic environment, too)
feed on dead bodies and waste products of other organisms - ex: fungi, many bacteria, vultures, earthworms
energy flow through an ecosystem quantified as biotic production
Amount of carbon per unit area (g/mxm)
biotic production looked at as a rate (carbon/meter squared/year)
gross primary productivity
(GPP) - rate at which all primary producers in the ecosystem turn solar energy into stored chemical energy via photosynthesis
net primary productivity
(NPP)- rate at which energy is incorporated into the primary producers bodies through growth and reproduction
equation for net primary production
NPP = GPP - R (energy lost through respiration)
ecological efficiency and its three components
rate of energy transfer from one trophic level to the next
1. heat loss (energy consumed for respiration and other metabolic processes)
2. biomass unavailability - energy not consumed form lower trophic level because it is inedible or inaccessible
3. indigestibility - energy is not assimilated from consumed biomass because it is indigestible
what accounts for inequality amongst species?
traits of species and their abundance
three major kinds of species
dominant species (large effect due to high abundance), keystone species (have a disproportionately large effect on ecosystem relative to their abundance - ex: sea star of PNW consumes mussels and thus frees up space for other species to occupy ), ecosystem engineers (altering physical environment - ex: beaver's dam changes flowing water to still water)
change in species membership of an ecosystem over time
ways in which herbivores deal with protein limitations
1) selective feeding (only eating certain parts of the plant)
2) compensatory feeding (taking in tons of food)
resistance vs. tolerance
resistance - traits that exclude many species that might otherwise want to feed on plants (prevents an attack in the first place)
tolerance - being able to withstand feeding of herbivores and regrow
which areas have the highest primary production?
along continental coasts where nitrogen levels are the highest
four compartments of global ecosystem
4) fresh waters
pattern of movement and transformation of a chemical element through organisms and reservoirs (pools) in the physical environment
buildup of carbon dioxide that traps heat in the atmosphere
briefly compare antagonistic and mutualistic species interactions
in antagonistic species interactions, the population size of one species (predator or parasite) increases and the population of the other species (prey or host) decreases. in mutualistic interactions, the population sizes of both species increase.
define aposematism and briefly explain its role in batesian and mullerian mimicry
refers to unpalatability combined with warning signals to potential predators. in batesian mimicry, the model is aposematic, while the mimic is not (because it is palatable). in mullerian mimicry, all species involved in mimicry are aposematic.
describe the population dynamics that can arise from specialized predator-prey and parasite-host interactions
specialized predator-prey and parasite-host interactions can cause cyclical population fluctuations in interacting species. the population cycles are typically coupled, but with a short lag between cycles.
briefly describe two ways in which antagonistic interactions can affect the species membership of an ecological community
antagonistic interactions can reduce species membership in an ecological community through predatory or parasitic exclusion of species. can also increase species membership in a community if the predator or parasite controls populations of prey or hosts that would otherwise exclude another species from the community. for example, in a trophic cascade (such as a wolf) can control an herbivore population (such as an elk), thereby allowing a viable population of plant (such as aspen tree).
in highly species-specific interactions, coevolution can cause...
co-cladogenesis, escalation of traits possessed by interacting species, like an arms race, and evolutionary transitions between antagonism and mutualism
briefly explain and give an example of "food for defense/protection mutualism"
in a food for defense/protection mutualism, one species gains food from the other, while the other species gains defense or protection from its enemies. for example, ants commonly provide protection to either plants or sap-feeding insects in response for nutrient-rich food rewards (ex. food bodies, honeydew, extrafloral nectar). the acacia-ant example also works here, but there is additionally a shelter benefit provided to ants by the acacia plant.
characteristics of microparasites
extremely small body size relative to host, undergoing multiple generations and population evolution within a single host, infections not typically resulting in death of the host
explain why the mutualism between animal seed dispersers, such as many birds, and woody trees is so important to the plant community structure of rainforests
animal seed dispersers are likely to transport seeds much farther away from a parent plant than wind, gravity or water dispersal of seeds. in tropical rainforests, this is critical because a seed's chance of survival, growth, and reproductive maturity is much greater when it is far from a mature plant of the same species. the distance-dependend mortality effect is due to host-specific parasites and herbivores that occur at much higher densities in the vicinity of mature plants. in recent years, the main culprits are parasitic fungi in the soil surrounding mature individuals of their specific host trees.
compare the coevolutionary dynamics of grazing/browsing herbivores and plants to those of dietary specialist herbivores and their host plants
the coevolutionary dynamics of grazing/browsing herbivores are of a diffuse nature. that is, reciprocal adaptations result from collective, rather than specific interactions between herbivores and plants. on the other hand, specialist herbivores and their host plants are commonly engaged in pairwise coevolution, akin to that of parasite-host interactions. reciprocal adaptation occurs via natural selection imposed by one species on the other.
herbivores counter the chemical defenses of their host plants by...
compensatory feeding, detoxification of ingested plants secondary metabolites, and specialized mouthparts and large mandibular muscles
briefly explain induced chemical defense in plants
plants can respond to herbivory by increasing their chemical defenses or resistance. this occurs via the plant's recognition of herbivore feeding damage (often due to salivary proteins), triggering a biochemical pathway mediated by jasmonic acid (jasmonate) that ultimately results in increased expression of genes coding for resistance factors, such as protease inhibitors, in the plant's tissues being attacked.
four essential components of a food web
source of energy, primary producers, consumers, detritivores
in food webs, trophic efficiency is limited by
energy lost due to metabolic activity, food not consumed, and food not assimilated into biomass of the consumer
list the four compartments of the global ecosystem
atmosphere, oceans, fresh waters, land
a species that has large influence on ecosystem structure and dynamics due to alteration of the physical environment
compare and contrast the factors living net primary productivity in terrestrial versus marine ecosystems
in terrestrial ecosystems, NPP is limited primarily by temperature and precipitation on a global scale (although other factors can be limiting at a more local scale). in marine ecosystems, nutrients, and especially usable nitrogen, limit NPP.
briefly explain two mechanisms to explain the frequently observed relationship between species richness and ecosystem dynamics
niche complementarity among species in an ecosystem can cause a relationship between species richness and ecosystem dynamics. this means that more species in the community can consume more of the available resources in the ecosystem than can a single species or small number of species. a second mechanisms is the driver-passenger hypothesis. here, species in the community have unequal effects on the ecosystem dynamics. drivers have large effects, while passengers have negligible effects. this mechanisms could cause a positive relationship between species richness and ecosystem dynamics if more driver species occur, by chance, with greater species richness.
briefly explain the greenhouse effect
the greenhouse effect occurs as earth's atmosphere traps heat energy from solar radiation hitting the Earth's surface. the chemical composition of the atmosphere determines the heat-trapping capacity, with water vapor and carbon dioxide playing a large role. in addition, methane and nitrous oxide exert a large effect, despite their relatively small concentrations.
briefly explain one positive and one negative effect of anthropogenic nitrogen fixation
anthropogenic nitrogen fixation has increased net primary production in human agriculture through the use of chemical fertilizers. in doing so, it has increased the global food supply for human beings (so-called green revolution). the downsides of the manufacture and use of nitrogen fertilizers include increased greenhouse gas emissions into the atmosphere as well as nitrogen pollution in terrestrial and aquatic ecosystems. in the latter, nitrogen fertilizer runoff causes "dead zones" due to the anoxic conditions resulting from eutrophication (extreme algal blooms) and rapid microbial decomposition of unconsumed biomass.
intrinsic rate of increase in the exponential population model
a group of individuals born within the same time frame, or age class
proportion of original cohort to survive to age x
proportion of individuals of age x who die before reaching age x + 1
intraspecific competition and some effects
individuals of the same species (within the same population) competing with each other for resources (this is a negative-dependent density factor)
1) competition of different phenotypes leads to adaptive evolution
2) intraspecific competition for resources affects population growth
3) sometimes spatial arrangement of individuals in a population follows intraspecific competition. (leads to a more regular dispersion pattern)
interspecific competition and consequences
competition between different species of organisms. has a negative effect on the population growth of both species. (ex: grizzly bear attempts to take over kill of wolves). can lead to character displacement, competitive exclusion,
examples of how density dependent changes in survival to reproductive age via interspecific competition play out in different organisms
1) bird population - # of
limit population growth if not enough are required
result of competition. competition limits how much food they can acquire in any given place. so, within each lizard species, smaller (younger) and larger (older) exist. small ones eat smaller insects, larger eat larger. they can coexist in the same spatial area if there's this difference in body size. when you have different species they tend to partition themselves on different parts of the tree.
how communities of organisms are structured
groups of species that exploit the same resource, but in lisghtly different ways, making the resource less likely to be preempted
competitive exclusion principle
not all species can coexist. species competing for the same resource in the same way cannot coexist for long -- one or both of those species will become locally extinct. (paramecium species)
set of conditions (both biotic and abiotic) under which a population can persist. same ecological niches allow two of the paramecium species to coexist.
The process by which natural selection drives competing species into different patterns of resource use or different niches. Coexistence is obtained through the differentiation of their realized ecological niches
one that a species can occupy in the absence of other competition that might exclude that species from occupying that niche (kind of a potential niche of a species) (defined by physiological capabilities of species)
the actual niche that a species occupies in an ecological community (defined by its interactions with other species)
Competitive ability and stress tolerance (rock barnacle is a superior competitor but its weakness is its intolerance to desiccation)
set of physical and biological conditions a species requires to survive, grow, and reproduce
Recommended textbook explanations
Miller and Levine Biology
Joseph S. Levine, Kenneth R. Miller
Johnson, Peter H. Raven
Biology The Dynamics of Life
Modern Biology: Student Edition
Janet L. Hopson, Postlethwait
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