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