Test 3 Flashcards
How would you assess the importance of density-dependent processes in bighorn sheep?
A. look at correlations between sheep populations and rainfall
B. look at correlations between reproduction/mortality and rainfall
C. look at correlation between reproduction/mortality and sheep population size
Look at correlations between reproduction/mortality and sheep population size
Stable populations fluctuate within relatively ___ limits
narrow
Population stability is achieved by the sum of both
density-independent and density-dependent regulatory factors
T or F? The population may be stable but not necessarily at equilibrium
T
Equilibrium implies regulation via
density-dependent factors
T or F? Density-dependent control always results in stability
F
What is a metapopulation?
a group of populations in a landscape composed of habitat of varying quality and linked by migration
The metapopulation is comparatively ___ because it’s composed of a set of populations that fluctuate independently
stable
Life history comprises:
- the pattern of development and growth
- life span
- the timing and quantity of reproduction
Selection’s perfect organism would
- be mature at birth
- continuously produce lots of high-quality offspring
- live forever
The amount of energy that is available to an organism over the course of its life is
finite
Finite energy drives the importance of trade-offs in the evolution of organismal life histories
principle of allocation
Life span (i.e. senescence) is influenced by an organism’s ability to keep itself going at the expense of
decreases in potential reproduction
What are the trade-offs of reproduction?
- when is sexual maturation optimal?
- what is the optimal number of offspring to have?
- what is the optimal parental investment for each offspring?
Life history traits are optimized by
natural selection to maximize parental fitness
Adaptive life history strategy evolves as
the life history traits evolve in response to ecological conditions
Life history traits do not evolve in isolation and are linked via
energy trade-offs (principle of allocation)
Investment in each life history trait has a
benefit and a cost to the organism
For each life stage, there is an optimal
investment into a certain life history trait
Investment beyond the optimum investment into a certain life history trait,
reduces fitness by limiting energy available for other important functions
What is teleology?
the idea that purpose exists in evolution in the same sense that it does for human intention
T or F? Evolution has no pre-designed or intentional goal
T
T or F? “Strategy” implies a conscious choice by the organism
F
Optimal life history does not mean the best possible, it means
the best of those existing in a certain population under certain environmental conditions
-life history strategy only needs to be “good enough”
T or F? Trade-offs mean that it is the overall strategy rather than a single life history trait that determines fitness
T
The components of the life history strategy evolve as
an integrated unit
Reproductive vale (Vx) of an organism is
the expected reproductive contribution of an individual of age x to the next generation
Vx
- changes over the course of the life span
- is closely tied to fitness
Lt/Lx is
the probability of an individual of age-class x surviving to a given future age-class
Lt/Lx is determined by
the interaction of the Lx and bx columns
Vx often increases with age to a maximum just as the organism enters
its reproductive years
As birth rate and survivorship decline with age,
Vx declines
Optimal life history strategy formula
Vx = t=tmax
Σ (Lt/Lx) (bt)
t=x
The life cycle comprises three key developmental features
- the process by which an embryo becomes an adult
- the presence of dormant stages during development
- the development and constancy of the organism’s sex
What is a simple life cycle?
juveniles develop from the fertilized egg, grow into adults whose gender is determined genetically, live out their lives as active adults, and eventually die
-ex: humans
A complex life style includes:
- changes in the body plan, (including resting stages)
- change in the individual’s gender
- ex: amphibians, insects
What is direct development?
when the adult develops directly from the fertilized egg without the larval stage
What is metamorphic development?
development that includes a larval stage that is often radically different from the adult individual
What are the costs of metamorphosis?
- significant energy expenditure
- vulnerability to predation at certain stages
What are the advantages of metamorphosis?
- specialization on different functions of different life stages
- exploitation of different ecological niches
- reduced competition among larvae and adults
What is neoteny?
the development of sexual larval forms that no longer metamorphose into adults
-ex: salamanders
Where is neoteny most common?
in extreme environments or where larval habitats are more productive
What is a resting stage?
developmental stage in which the organism is dormant, inactive, and often resistant to harsh environmental conditions
-ex: seeds, spores, cysts
In a simple life cycle, an individual’s sex
is determined early in development and remains constant throughout life
In sequential hermaphroditism,
sex changes during the life span
What is protandrous sequential hermaphroditism?
when an individual is first male and then female
What is protogynous sequential hermaphroditism?
when an individual is first female and then male
What is senescence?
late-life decline in fertility and probability of survival
What does the rate-of-living theory suggest?
- bodies wear out
- eventually bodies accumulate damage: errors in DNA replication and translation, build up of poisonous metabolites
- Organisms are adapted to resist wearing out as long as possible, but there isn’t the genetic variation to extend life further
What predictions does the rate-of-living theory make?
- aging should be correlated with metabolic rate
- there should not be the opportunity to select for longer life spans
- BOTH PREDICTIONS DON’T HOLD IN GENERAL
Life span is NOT correlated with
metabolic rate (higher metabolic rates doesn't mean shorter lives and lower metabolic rates doesn't mean longer lives)
T or F? Longer life span can be selected for
T
Rate-of-living can be thought of as
“the result of intrinsic physiological limits on cells and tissues”
What does the LIMITING SOMA THEORY (hypothesis 1) suggest about why organisms age?
- limiting resources devoted to reproduction result in decreased somatic maintenance
- mutation that diverts energy toward early reproduction diverts energy away from maintenance and repair
What is another hypothesis (hypothesis 2) about why organisms age?
- the intensity of natural selection declines with age
- genes whose main effects occur after the peak in Vx are not subject to the same intensity of selection as those that occur when Vx is high or increasing
- deleterious mutations then accumulate and cause senescence
What does the evolutionary theory of aging suggest?
deleterious mutations with effects that begin late in life are harder to remove from the population
What does hypothesis 3 suggest about why organisms age?
- pleiotropic effects of genes: the action of a single gene that affects several phenotypic traits
- genes that benefit younger individuals whose reproductive value if high will be selected for even if they have deleterious pleiotropic effects that occur in old age
Why is reproductive effort a cost that must be budgeted?
- energy spent on reproduction can’t be spent on other functions
- early reproduction can shorten lifespan
If trade-offs are optimized, reproductive effort should be ,maximized to
get the most offspring into future generations
T or F? Higher reproduction increases fitness
F; larger clutches in pairs of pied avocets led to higher chick mortality, decreasing net reproductive rate
Are there adaptive reasons to produce fewer offspring than physiologically possible at any one time?
yes
T or F? There is usually very little variation in offspring size in most species
T
What are iteroparous organisms?
organisms that reproduce multiple times
What are semelparous organisms?
organisms that reproduce just once
What are conditions that favor iteroparity?
high adult survivorship and low juvenile survivorship
What are conditions that favor semelparity?
low adult survivorship and high juvenile survivorship
What are characteristics of competitive plants?
- experience low stress and low disturbance
- are more limited by competition between individuals than external factors
- produce few well-provisioned seeds that allow seedlings to compete strongly
What are characteristics of stress-tolerant plants?
- inhabit physically demanding habitats where stress is high and disturbance is low
- challenged by slow growth
- show iteroparity and greater allocation to survival
What are characteristics of ruder plants
- inhabit environments with low stress and high disturbance
- adapted to rapidly exploit ephemeral conditions
- show high growth, short life span, semelparity, and long resting stages
What are characteristics of k selection?
- stable environment
- high competition
- high and stable density (near k)
- parental care
- iteroparity
- late age at maturity
- small clutches
- large offspring
What are characteristics of r selection?
- fluctuating environment
- low competition
- density fluctuates- often low
- semelparity
- large clutches
- early age at maturity
- small offspring
R-selection normally occurs in a ___ climate
variable and/or unpredictable
K-selection normally occurs in a ___ climate
fairly constant and/or predictable
R-selection is associated with ___ mortality
-often catastrophic, non-directed, density independent
K-selection is associated with ___ mortality
more directed, density dependent
What type of survivorship is r-selection?
often type 3
What type of survivorship is k-selection?
usually type 1 or 2
The population size characteristic of r-selection is
variable in time, non-equilibrium
The population size characteristic of k-selection is
fairly constant, equilibrium
What is favored by r-selection?
- rapid development
- early reproduction
- small body size
- semelparity
What is favored by k-selection?
- slow development
- greater competitive ability
- lower resource thresholds
- delayed reproduction
- larger body size
- iteroparity
What length of life is associated with r-selection?
short
What length of life is associated with k-selection?
long
R-selection leads to
productivity
K-selection leads to
efficiency
Where would ruderal plants fall in the r-K dichotomy?
r-selected
Evolutionarily, which is better?
A.Quality
B.Quantity
C.It depends
C. It depends
Bet-hedging strategies
reduce the magnitude of each reproductive event, thus spreading the risk over multiple events
Among species, the proportion of seeds that germinates in any year is negatively correlated with
variation in reproductive success
Life history strategy is the product of
evolution
Each organism has a finite amount of energy to devote to life functions such as development, maintenance, and reproduction. Therefore, it must allocate that energy in ways that
maximize fitness
The reproductive value measures
the expected contribution of an individual age x to the next generation
Life history is affected by both
genetic mechanisms and phenotypic plasticity
Finite energy available to an organism leads to
trade-offs in life history characters
Senescence results from the combination of
external and internal factors that increase mortality as a function of age
Selection has a genetic component, and therefore
selection can increase life span
What are the three mechanisms that contribute to the evolution of senescence?
- trade-offs between reproduction and maintenance (limiting soma)
- late-effect deleterious mutations
- antagonistic pleiotropy
What are the costs/benefits of metamorphosis?
COSTS:
-requires energy and complex genetic regulation
BENEFITS:
-allows the organism to exploit resource-rich environments and organize the body plan for specific functions
Resting stages
allow the organism to avoid harsh physical conditions
When would it be adaptive to change sex during the life span?
when male and female success varies with age, size, resources, or the social system
The optimal reproductive output is not necessarily the
physiologically maximum possible
There is a trade off between number of offspring and
the probability of their survival
There is a trade off between offspring quality and
offspring number
The age-specific reproductive rate (bx) and the age-specific survival rate (Lx) are ___ connected
reciprocally
Reproduction has a ___ cost, and the reproductive pattern is a response to the ___
mortality; mortality schedule
Reproductive life history is a response to the species’
unique ecology
What frameworks organize interactions according to the key ecological forces acting on reproduction?
r/K selection, Grime’s triangle, and bet-hedging theory
Important selective force imposed by ecology are
- quantity vs. quality offspring
- the mean reproductive output vs. the variation in reproductive output
What is competition?
an interaction between individuals over a limiting resource that leads to decreased fitness of both individuals and decreased population growth rate
What is intraspecific competition?
competition among individuals of the same species
-leads to reduced fitness of individuals
What is the formula for intraspecific competition?
dN/dt = rN(1-N/K)
Intraspecific competition is an example of
logistic growth (s looking curve)
What is an example of intraspecific competition?
self-thinning in plants
What is interspecific competition?
competition between DIFFERENT species
What does interspecific competition lead to?
decreased mean fitness and reduced population size in at least one species
What is a specie’s niche?
the set of biological and physical resources that determine growth, survival, and reproduction
What does Gause’s competitive exclusion principle state?
no two species can coexist on a single limiting resource (i.e. occupy the same niche)
If niche overlap is significant, one species will
outcompete the other
Corollary
niches of coexisting species must differ
What is the formula for interspecific competition?
dN/dt = r(max)N(K-N/K)
What are the formulas of population growth for two species?
For species 1:
dN1/dt = r(max1)N1(K1-N1/K1)
For species 2:
dN2/dt = r(max2)N2(K2-N2/K2)
N1 and N2: pop sizes of species 1 and 2
K1 and K2: carrying capacities of species 1 and 2
r(max1) and r(max2): respective intrinsic rates of increase of species 1 and 2
What are the equations for interspecific competition between species 1 and species 2?
For species 1:
dN1/dt = r(max1)N1((K1-N1-alpha12N2)/(K1)
For species 2:
dN2/dt = r(max2)N2((K2-N2-alpha21N1)/(K2)
Competition coefficients express
the competitive effect of one species on another
Competition coefficients are expressed in terms of
intraspecific equivalents
If α12>1
the competitive effect of an individual of species 2 on the pop growth rate of species 1 is GREATER than that of an individual of species 1
If α12<1
the competitive effect of an individual of species 2 on the pop growth rate of species 1 is LESS than that of an individual of species 1
Interspecific competition is ___ than intraspecific competiton
weaker
Populations of species 1 stop growing when
N1 = K1-α12N2
Populations of species 2 stop growing when
N2 = K2-α21N1
Zero population growth occurs at
carrying capacity minus any effect of the density of the competitor
Above an isocline of zero growth, the population of a species is
decreasing
Below an isocline of zero growth, the population of a species is
increasing
What is an isocline of zero population growth?
a line along which there is neither an increase of a decrease that divides the combinations leading to an increase from those leading to a decrease
Each species isocline represents combinations of N1 and N2 at which
population growth rate of the respective species is zero
Only below the isocline can population growth be
positive
The formula N2 = K1/α12 represents
the carrying capacity of species 1 expressed in terms of numbers of individuals of species 2
If the competition coefficient α12 = 1, adding individuals of species 2 has ___ on species 1’s population growth rate as adding individuals of species 1
the same effect
There are only three possible outcomes of merging two species isoclines in a single plot. What are they?
- extinction of species 1
- extinction of species 2
- coexistence of the two species
On an isocline graph whichever specie’s line is further right, that species
wins
If isoclines cross, the equilibrium point can either be
stable or unstable
If individuals of both species compete more strongly with individuals of the other species than they do with themselves, both species can reach densities high enough to drive the other ro
extinction
The equilibrium point at the crossing of the isoclines is stable only if
both species have less competitive effect on the other species than they have on themselves
Stable coexistence occurs when the effects of intraspecific competition are greater for ___ species than is interspecific competition
both
When K1
there is stable coexistence
For stable coexistence to hold
- the values of α must be small
- the values of K1 and K2 must not be too different
What are the assumptions of the L-V competition model?
- closed system (=no migration)
- r is a constant (=fixed intrinsic growth rate)
- K is a constant (=environment invariant)
- α is a constant (=no density-dependence)
- all individuals within species are equivalent (=no variation in phenotype)
- no time lags (=instant responses to changes in abundance of other species)
What is an evolutionary effect of competition?
character displacement
- competition-driven divergence of the niches of two competing species
- driven by lower fitness of individuals with trait values that overlap with those of individuals of another species
Character displacement may lead to
adaptive radiation
Limited resources lead to competition
between species as well as within species
Interspecific competition is empirically demonstrated by showing that
- the resource is limiting
- the interaction between the species has a negative impact on one or both of them
The ecological niche is central to competition because
it is based on the use of critical resources
What is the most important short-term effect of competition?
competitive exclusion
What is an important long-term (evolutionary) effect of interspecific competition?
character displacement
Coexistence is possible if
- the niche overlap of the two species is small (competition coefficients are low)
- the carrying capacities of the two species are similar (K values are not too different)
Co-evolving species interact
ecologically
Coevolution occurs when
changes in the genetic composition of populations of at least two species reciprocally affect each other
What is competition?
when two or more species use the same limiting resource, or seek that resource, to the detriment of both species
What is mutualism?
when two species live in close association with one another to the benefit of both
What is predation?
when one organism eats all or part of an animal species
What is herbivory?
when one animal eats all or part of a plant species
What is parasitism?
when two species live in physically close association, in which the parasite depends metabolically on the host
What is parasitoidy?
when one species spends a significant portion of its life attached to or within a single host that it eventually kills
What is the interaction of exploitation?
(+,-)
What is the interaction of commensalism?
(+,0)
What is the interaction of mutualism?
(+,+)
What is the interaction of competition?
(-,-)
What is the interaction of symbiosis?
(+,-,0;+,-,0)
What is commensalism?
an interaction between two species in which one benefits, whereas the other doesn’t benefit, but isn’t harmed (+,0)
What is obligate mutualism?
when one or both species are so dependent on the interaction that they can’t live in the absence of the other species
What is facultative mutualism?
when the mutualistic relationship is not required for the survival of the two species
If neither species benefits from an interaction it is
competition
If both species benefit from an interaction it is
mutualism
What is symbiosis?
an intimate association between different organisms, in which one lives on or in the other
What are exploitative interactions?
when one species benefits from exploiting another as a food source
What types of heterotrophy does exploitative interactions encompass?
- predators
- parasites/parasitoids
- herbivores
Predator-prey interactions are an example of
coevolution (the process in which each species acts as a selective force on the other)
What are examples of crypticity?
- color matching
- break up the outline
- countershading
- hide the eye
What are some prey adaptations to avoid predation?
- herd and school behavior (bison,fish)
- predator swamping (insect emergence)
- escape and defense (blue tailed skink)
- toxins/aposematic coloration (poison frogs)
What is Mullerian mimicry?
when groups of toxic/unpalatable species resemble one another
What is Batesian mimicry?
when benign species resemble a toxic or palatable one
What is the coevolutionary arms race?
a series of escalating adaptations and counter-adaptations evolving in an exploitive species interaction
What are challenges facing predators?
- prey detection
- capturing and subduing prey
What are two methods of capturing and subduing prey?
- ambush predators
- active predators
What are some hunting strategies predators use?
- solitary predators (cheetah)
- group hunting (wolves, wild dogs)
- cooperative hunting (orcas)
What is optimal foraging theory determined by?
the net gain or loss of energy for different predation strategies
What are two kinds of energetic constraints on predators?
- maximizing energy, if energy-limited
- maximizing energy per unit time
Are predator “strategies” subject to evolution via natural selection?
yes
What does s represent?
the search time (time spent searching for prey)
What does h represent?
the handling time (time spent capturing, subduing, and consuming prey)
What does E represent?
the energy gained from consuming a diet item
What does Ei represent?
the energy gained from consuming a NEW diet item
What does h(i) represent?
the handling time for a NEW diet item
The diet of a an organism should remain specialized unless
a new food item provides a major energy gain relative to the average cost of searching and handling
What is the equation for the optimal foraging theory?
Ei/h(i) >= average E/ (average h + average s)
New items will be added to an organism’s diet only if
the total energy gain is larger with the new item than without it
Predators with long search times, s, and short handling times, h, should be
generalists
Predators with long handling times, h, and short search times, s, should be
specialists
To forage optimally in a patchy environment, the predator should maximize
the rate of energy gain
E/(t + s)
t: average time of travel to a new patch
s: how long the predator stays in the patch
Diseases that are easily transmitted between hosts will tend to be selected for
increased virulence
Pioneer species are often
fugitive species
Commensalism best describes the interspecific relationship that affects
species A positively and species B neutrally
The costs of metamorphosis include
significant energy expenditure and vulnerability to predation at certain stages
Primary and secondary succession differ in
- the intensity of the disturbance
- the effect on soil and nutrients
The Grandmother Hypothesis
- depends on indirect fitness
- helps to explain long life after a female can no longer reproduce
Pioneer species
can tolerate harsh abiotic conditions
A predictable environment tends to encourage
K-selection and small clutches
Only distantly related New World monkeys co-occur. This is a result of
competition eliminating similar species
Competitive networks A.are based on apparent competition B.are the result of facilitation C.are caused by the ghost of competition past D.are caused by keystone predators E.none of the above
none of the above
In Lotka-Volterra state-space plots, an isocline
determines where population growth is 0
T or F? Mimicry can evolve in a mutualistic relationship
T
What characteristics are required to define an EVOLUTIONARY population?
a group of individuals that mate at random and the boundaries determined by barriers to gene flow and mating
The Lotka-Volterra models show that coexistence is more likely if
niche overlap is small and carrying capacities are similar
Which of the following is NOT characteristic of interspecific competition?
A. one or more resources is limiting
B. The population size of at least one species decreases
C. The limiting resource does not change over time
D. Two or more species interact
E. none of the above
C. the limiting resource does not change over time
According to the competitive exclusion principle
two species can’t coexist on the same limiting resource
Character displacement
is the result of selection to decrease niche overlap
T or F? In general, organisms that produce few offspring produce smaller offspring than those organisms that produce many offspring
F
T or F? In some fish populations, older mothers produce more and “better” offspring than younger fish
T
T or F? Intraspecific competition for limited resources can play a key role in slowing population growth at high densities
T
T or F? Character displacement reduces interspecific competition and allows resource partitioning
T
T or F? It is possible for a prey organism to grow so large that predators can no longer effectively kill it; ecologists call this a “refuge in size”
T
T or F? Mutualism evolves when the relationship increases the fitness of species involved
T
T or F? Measures of community structure are not affected by sampling effort
F
T or F? In general, more complex plant communities support simpler animal communities
F
T or F? In general, more complex plant communities are found in areas of low soil fertility
T
T or F? Mutualists can’t be keystone species
F
T or F? In general, primary productivity in freshwater environments is limited by phosphorous, while nitrogen limits primary productivity in marine environments
T
Which of the following environments for germinating seed is most likely to favor a plant species that makes many small seeds compared to one that makes fewer larger seeds? A. nutrient limitation B. competition from established plants C. shade D. deep burial in soil E. disturbance
E. disturbance
In species where adult survival is lower, organisms
- begin reproducing at an earlier age
- invest a greater proportion of their energy budget into reproduction
Which of the following is not an example of a population characteristic used to classify life histories?
A. intrinsic rate of increase (r(max))
B. competitive ability
C. juvenile survivorship (Lx)
D. population density
E. all of the above are examples of population characteristics used to classify life histories
D. population densities
Cause’s “competitive exclusion principle” states that
no two species with identical niches can coexist indefinitely
Field experiments differ from laboratory experiments in that
laboratory experiments allow control of variables not of direct interest, while in field experiments these typically vary
In the Lotka-Volterra competition equations, the parameter α12 related to the
effect OF species 2 ON population growth rate OF species 1
In the Lotka-Volterra predation model, a prey (host) population in the absence of predators would
grow exponentially
In the Lotka-Volterra predation model, a predator population in the absence of prey (hosts) would
decline as predators die
In most ecological communities, we find
more moderately common species than rare or very common ones
Joseph Connell’s “intermediate disturbance theory” proposes that
species diversity is highest at intermediate frequencies of disturbance
A keystone species is one
whose feeding activities have a disproportionate effect on the structure of its community
