Ecology and Evolution Quiz Three
what part of differential equation for logistic growth is the "brakes"
1 - N/K
Life table
A summary of how survival and reproductive rates vary with the age of organisms.
Life history traits
Age at first reproduction duration and schedule of reproduction Number of offspring Size of offspring Lifespan Maintenance
Why do all populations eventually reach a carrying capacity
Because Earth is a finite planet and cannot support ever-increasing numbers of any species. Something will eventually limit them.
Sequential hermaphroditism
Changes in sex during the course of the life cycle
David Lack experiment 1947
Clutch size (number eggs produced per reproductive cycle) limited by maximum number of young parents can raise at once. In clutches with fewer eggs, chances of survival better. When they attempt to rear too many, offspring will be more likely to starve. Larger clutches at higher latitudes bc longer daylight
Why do clownfish bother being nonbreeders under dominance of single breeding female and male
Depend on the protection of anemones for survival. More likely to survive under this system than try to find another anemone or just chill in the ocean
Density independent factors
Effects on birth and death rates independent of the number of individuals in population ex: temperature, predation, catastrophic events
T/F density independent factors are an important method to regulate population size
False - they do not regulate population size because they do not consistently increase population size when small and decrease when large
T/F survivorship curves are constant for each species
False. They can vary among populations of a species, between males and females, among cohorts.
Seahorse mating
Female transfers unfertilized eggs to male. male stores eggs and fertilizes them. Males are more likely to mate with larger females and eggs from larger females are more likely to be successfully transferred to males and develop into viable offspring. Female competition - bigger, fancier fins, brighter colors
What happens when operational sex ratio is female-biased, i.e. more females are ready to mate than males
Females compete over limited number of reproductively ready males. females become larger and more aggressive than males, and they possess territories that include male nests. they mate with all males in this territory and then the males take care of the chicks.
Effect of removing ovaries of lizards
Females without ovaries grew faster because they had free resources to invest in growth. Females with ovaries invested resources to grow eggs
Life-history trade-off in guppies
Guppy populations in areas of high predation have more, smaller offspring which reproduce earlier. populations in areas of low predation have fewer, larger offspring which reproduce later
How is miscarriage adaptive
If fertilized eggs carry harmful mutations spontaneous abortion often happens
Trade offs occur when
Individuals allocate their limited energy or other resources to one structure/function at the expense of another
Type II survivorship curve
Individuals have an approximately constant chance of surviving from one age to the next throughout their life. On log scale, straight negatively sloped line
What huge event made the human population start increasing super fast
Industrial revolution
Type III survivorship curve
Lots of young die but those that live are likely to stay living. On log scale, sharp drop and then slightly negative line.
Lack Clutch Size
Maximum number of offspring that a parent can successfully raise to maturity
What happens if larval habitat is extremely favorable for growth and survival
Metamorphosis is delayed or sometimes eliminated altogether (paedomorphism)
Western fence lizard shows size-number trade-off because
More eggs and smaller size in Washington, Less eggs and bigger size in california
Lack's hypothesis on clutch size
Most productive clutch size should be the clutch size most commonly observed in nature.
How to estimate survivors
Multiply number of individuals in each age class (Nx) by survival rate for the age class (Sx).
What is the quantity-quality trade-off expression? define variables
N = R/C N = number of offspring R = reproduction C = cost (size of offspring, essentially)
Exponential growth equation
N(t) = N(0)e^rt dN/dt = rN
Type I survivorship curve
Newborns, juveniles, and young adults have high survival rates and death rates do not begin to increase greatly until old age. Ex: US population. on log scale, it's straight for a long time then drops off
Geometric growth equation
Nt+1 = λNt
Nx
Number of individuals alive at age x
Number of young song sparrows at different densities graph (figure 10.15 CE)
Number of young per female that survived to independence declined with population density. Nesting pairs that were fed more reared more young to independence
Life history
Pattern of investment an organism makes in growth and reproduction
Explain a way age structure can influence whether population increases or decreases in size
Populations w members of around 20-30 years old will grow more rapidly than ones w members 50+ years old bc more individuals at reproductive age
What does dN / dt represent
Rate of change in population size at time T
When Sinervo raised fence lizard eggs and removed some yolk from some
Reduced eggs developed faster but produced smaller hatchlings
If λ is constant over time, what happens to the proportion of individuals in each age class?
Remains constant - "stable age distribution"
paedomorphism
Retention of juvenile features in the adult
Common propagule tradeoff
Size vs. number
When age-specific survival and fecundity / birth and death rates are constant over time, one should expect λ to do what?
Stay constant over time
Static life table
Survival and reproduction of individuals of different ages are recorded during a single time period.
Fecundity (Fx)
The average number of offspring produced by a female while she is of age x
How is size hierarchy maintained in clownfish
The largest fish in a reef is the female. The rest are "ranked" so each fish is smaller than the one ahead of it in rank. Largest male - breeding. If a fish grows to be too close in size to one of its anemone-mates a fight results which usually ends in smaller fish being killed or expelled
Selection favors the optimal strategy for reproduction. What does this mean?
The one that maximizes the number of offspring that survive to maturity
Age structure
The proportions of the population in each age class
How do male sand gobies regulate offspring number
They eat eggs if oxygen concentration is low because it raises the probability of surviving for the ones left
Why do Seychelles warbler manipulate sex ratio in direction opposite to expected
They produce males when they're in worse conditions so that the male birds can fly away and search for different territories. In better conditions, they produce more females so they can stay behind and help mother
Age-specific survival rate. (Sx)
This is the chance that an individual of age x will survive to the age x + 1.
Survivorship (Ix )
This is the proportion of individuals that survive from birth to age x.
Doubling time
Time it takes for N0 to become 2N0 td = ln(2)/r
T/F selection can shape how organisms invest in reproduction over their lifetimes
True
Compare US survivorship and Gambian survivorship
US survivorship does not drop greatly until old age. Gambians die earlier. Gambians born in hungry season die even faster.
Exponential growth
When a population changes in size by a constant proportion at each instant in time
Geometric growth
When a population changes in size by a constant proportion from one discrete time period to the next
Population regulation
When one or more density-dependent factors cause population size to increase when numbers are low and decrease when numbers are high
Mechanisms to help small, vulnerable stages of life
Yolk Energetically expensive egg capsules - endosperm. kernels, meat of coconut Physical protection
How do insects who can do haplodiploidy (unfertilized = male; fertilized = female) regulate sex ratio?
You only need a few males, so when clutch sizes are larger there is a smaller male:female ratio (aka there are more females)
How does an organism reduce risk of investing
adjust the family - adjust number of offspring; manipulate ratio of sons to daughters
As densities increase it is common for
birth rates to decrease death rates to increase dispersal from population to increase --> decreased pop size
Dispersal is beneficial because
can reduce competition between relatives can allow organisms to reach new areas to grow and reproduce can increase chance of escaping regions of high mortality - pathogens, predators
K
carrying capacity
When number of young maturing is equal to mortality rate, the population size is called the
carrying capacity
Density-dependent factors
cause birth rates, death rates, or dispersal rates to change as density of population increases.
differential equation for logistic growth
dN/dT = rN (1 - N/K)
Logistic equation
dN/dT = rN (1 - N/K) rN - gas (1 - N/K) is net effect of limiting factors - brake
Higher annual fecundity in 14 different bird species was associated with
decline in annual survival rate
What happens to population growth rates at high densities
decline. both λ and r
Why are differences in morphology and behavior adaptive at different life cycle stages?
differences in selection pressures over the course of the life cycle. this can pair particular functions with particular stages and reduce some of the trade-offs that result from simultaneously optimizing multiple functions.
Small size benefits and drawbacks
drawbacks - vulnerable to predation, poor competitors for food, susceptible to environmental perturbations benefits - can perform essential functions impossible for large adult stages. dispersal, dormancy
Which affects an organism's fitness more: mutation that is beneficial early in life or late in life
early in life
Which affects an organism's fitness more: mutation that is deleterious early in life or late in life
early in life
propagules
eggs or seeds
r
exponential growth rate / intrinsic rate of increase
Cohort life table
follows the fate of a group of individuals born during the same time period until death
Assuming females limit reproduction, if a female is in bad condition, it is in her best interest to
have more females. they will probably reproduce at least once whereas males in poor condition may not
Assuming females limit reproduction, if a female is in good condition, it is in her best interest to
have more sons in good conditions who can mate with many partners
Austad's mainland vs island opossums
island opossums live 25% longer and have springier tendons (age slower). Fewer offspring = tradeoff.
Allocating resources to current reproduction can
lead to a decrease in an individual's growth rate, survival rate, or potential for future reproduction
General hypothesis - sex changes are timed to take advantage of
maximum reproductive potential of different sexes at different sizes
What happens to the operational sex ratio when both females and males cooperate in care of young
more even. males and females equally "tied down"
Dispersal
movement of organisms or propagules from birthplace.
The size of seeds a species produces is ________ correlated with the number of seeds it produces
negatively
When a population that is growing exponentially is ploted on normal vs. log scale
normal - J log - straight line
When eggs artificially removed, females will have more eggs. This leads to drop in
nutritional quality of later-produced eggs - lower lipid content. survivorship
When λ < 1 or r < 0
population decreases size
When λ > 1 or r > 0
population increases exponentially in size
When λ = 1 or r = 0
population size does not change
what part of differential equation for logistic growth is the "gas"
rN
Why do island opossums differ in reproduction
since they live longer, a slower, yet still successful, reproductive strategy evolved
Niche shift
size- or age-specific changes in an organism's ecological function or habitat
Benefit of being small for dispersal
smaller propagules disperse more readily and can travel farther
Benefit of being small for dormancy
smaller seeds, eggs, and embryos are better suited to dormancy than large multicellular organisms because they do not have to expend as much metabolic energy to stay alive
Dormancy
state of suspended growth and development in which an organism can survive unfavorable conditions
How to estimate newborns in following year
sum of (Fx)*(Nx)
Larvae often spend all their time
taking in food and turning it into body mass, without forming many complex morphological structures
The fact that the thickness of annual growth rings declines in Douglas fir trees that produce many cones indicates
there is a reproduction vs. growth trade-off
Drosophila males kept with virgin females vs. previously mated females
they spend more time and energy courting unmated females, so they had shorter life span (independent of size - males w larger size tend to live longer anyway) *take-away -* there is cost of sexual activity
Quantity-Size tradeoff
trade-off between investment in each individual offspring and number of offspring produced. Large investment --> less offspring; small investment --> more offspring.
When might you expect a niche shift to occur
when the organism reaches a size at which conditions are more favorable for its survival or growth in the adult habitat than in the larval habitat
lambda (λ) symbolizes
year to year population growth rate λ = (Nt+1/Nt) ex: if population at time 0 is 100 and at time 1 is 138, λ is 1.38
Why does dN / dt approach zero when population size nears carrying capacity
you can't change a lot growth wise anymore
Relationship between λ and r
λ = e^r r = ln(λ)
