Ecology Exam 2

What is a life history?

sequence, timing, and nature of events in an organisms life from birth to reproduction to death

What are life history traits?

traits shaped by natural selection that produce life history strategies, determine some aspect of life history of an organism or species

What are life history strategies?

general patterns of timing and resource allocation

What is evolutionary tradeoff?

when the investment in one life history trait increases/improves fitness, investment in a different life history trait decreases; arise from constraints

What is intrinsic growth rate?

growth rate, per individual per unit time; tells us whether a population is stable, growing, or shrinking

If r=0, what is happening with the population?

population is stable

If r>0 what is happening with the population?

population is growing

If r<0, what is happening with the population?

population is shrinking

What is fecundity?

potential reproductive capacity of an organism

What is per capita birth rate?

tells us the birth per individual in a population over time

What do life tables do?

summarize how fecundity and mortality vary with age, enable ecologists to estimate population growth more accurately, provide insight into why a population is growing or shrinking

What is survivorship?

fraction of an initial cohort that survives

What is lx?

survivorship

What are survivorship curves?

graph that plots age class and survivorship

What is a type one survivorship curve?

survivorship curve in which there is high survivorship in early and middle age, there is a quick decline/higher mortality as old age is reached; commonly seeing humans and large mammals

What is a type two survivorship curve?

survivorship curve in which there is a relatively constant mortality rate throughout life; think birds, lizards

What is a type three survivorship curve?

survivorship curve in which there is a low survivorship in young individuals and higher in middle and old age; think rabbits, insects

What is a fecundity schedule?

female’s expected reproductive output during each age class

What is mx?

fecundity

What is reproductive rate?

amount of females a female with give birth to that will replace her in following generations

How do we calculate reproductive rate?

sum of lxmx, add together the product of survivorship and fecundity at each age class

What is R₀?

reproductive rate

What is generation time?

average time from birth of a female until the birth of daughters

How do we calculate generation time?

(Σ xlxmx)/R₀

What is G?

generation time

What is the equation for population growth rate?

r = ln(R₀)/G

What is demographic transition?

when a population has high birth and death rates, there will eventually be a drop in death rates but birth rate will remain high and a population will swell, eventually a birth rate will drips and the population growth levels off

What is the principle of allocation?

states any resource used for one function reduces amount of energy available for another function

What is iteroparity?

organisms with multiple bouts of reproduction during an individuals lifetime, individuals will reserve some resources during each reproductive bout to invest in future reproduction

What is semelparity?

individuals reproduce just once before death, produce a huge amount of offspring and benefit by delaying reproduction to invest heavily in it

What is the MacArthur Wilson classification?

uses r and k selection

What are r selected species?

species that reproduce early and often, successful in environments where there are disturbances, life history maximizes their growth rate

What are k selected species?

species that are competitive and successful in stable, undisturbed environments, perform well when their population size is close to the carrying capacity

What is carrying capacity (K)?

max number of individuals that an environment can support

What are population pyramids?

pyramids that show age classes of males and females

What is happening with this population pyramid?

population is stable

What is happening with this population pyramid?

population is growing

What is happening with this population pyramid?

population is shrinking

What is the correlation between longevity of a mother and age of reproductive maturity, why?

positive correlation, is a mother lives longer she’ll spend more time maturing and growing to reproduce later

What is the correlation between fecundity and age of reproductive maturity, why?

negative correlation, a mother who reaches reproductive maturity later will produce less offspring in her lifetime (less fecund)

What is the correlation between size of offspring/eggs of a mother and age of reproductive maturity, why?

positive correlation, higher age of reproduction means more time to grow and therefore produce larger offspring

What is the correlation between size of mother and age of reproductive maturity, why?

positive correlation, the larger the mother the more energy taken to grown and therefore later reproduction

What is the correlation between fecundity and longevity, why?

positive correlation, the longer a mother lives the more offspring she will have throughout her life

What is the correlation between size of offspring/eggs and longevity, why?

positive correlation, the longer a mother lives the more energy she has to produce larger offspring

What is the correlation between size of mother and longevity, why?

can argue any relationship

What is the correlation between size of offspring/eggs and fecundity, why?

negative correlation, the less fecund the larger the offspring because less offspring are being born over the lifetime

What is the correlation between size of mother and fecundity, why?

negative correlation, the larger the size of the mother the more energy needed to grow and less to produce offspring so less fecund

What is the correlation between size of mother and size of offspring/eggs, why?

positive correlation, the larger the size of the mother the more energy for producing larger offspring

What is a grime classification diagram?

diagram that classifies types of plants based on competition, disturbance and stress

What are ruderal species?

plant equivalent of r-selected species, have a higher mortality and fast growth, high disturbance and low stress

What are stress tolerant species?

plants that have slow growth and a high reproductive rate, high stress and low competition

What are competitive species?

plant equivalent of k-selected species, fast growth rate, low disturbance and high competition

What survivorship curve are competitive species?

can be variable

What survivorship curve are stress-tolerant species?

type one

What survivorship curve are ruderal species?

type three

What life history traits do competitive species have?

constant environment, late reproductive maturity, fast growth rate, highly competitive, variable survivorship curve

What life history traits do stress-tolerant species have?

variable environment, type one survivorship curve, live long, reproduce late, low competition, slow growth

What life history traits do ruderal species have?

unpredictable environment, type three survivorship curve, short-lived, early reproduction, small offspring, fast growth, low competition

What is a geometric growth model?

growth model used for a population with discrete reproduction that is closed and has unlimited resources

What is discrete reproduction?

species in which there is a specific time/season for reproduction, reproduction once a year

What is the finite rate of increase (λ)?

ratio of a population at one time step to a population at a previous time step; N_t+1/N_t

What equation is N_t=N₀λ^t?

geometric growth rate, used to predict number of individuals in a population given a certain time period and finite rate of increase

What does a steeper slope indicate in the geometric growth model?

larger lambda/finite rate of increase

What is a exponential growth model?

growth model used for a population with continuous reproduction that is closed and has unlimited resources

What equation is N_t = N₀e^rt?

exponential growth equation; applied version where we can determine the population size at a certain time period

What equation is r=ln(λ/T)?

intrinsic growth rate calculated using finite rate of increase, used in the exponential growth model

What equation is dN/dt= rN?

used in exponential growth model, can help in determining instantaneous population growth

What is the difference in graphs between geometric and exponential growth?

exponential growth has a steeper slope than geometric growth

What is the logistic growth model?

growth model that in which as a population reaches carrying capacity the population growth slows

What equation is dN/dt=rN(1-N/K)?

logistic growth model equation

When N=K, what is happening to a population?

population is stable

When is population growth highest in the logistic growth model?

when carrying capacity is at half; K/2

What are density-dependent factors?

factors that influence r in proportion to N; impact depends on population density, the larger the N the greater the effect

What are density-independent factors?

factors that influence r regardless of N; impact is proportionally similar on small and large populations

What is a fundamental niche?

set of environmental conditions under which a species can survive and reproduce

What type of factors are we looking at to determine a fundamental niche?

abiotic factors and environmental constraints

What is a realized niche?

set of environmental conditions in which a species is actually found in nature

What type of factors are we looking at to determine a realized niche?

biotic factors and what organisms are in the area, looking at competition

What is niche partitioning?

when species form their own niches either with change in phenotype or area occupancy, allows for the coexistence of species while diminishing competition

What is competition?

when resources are limited, similar organisms compete for these resources

What is resource competition?

competition in which individuals compete indirectly by consuming a shared resource, both competitors are harmed

What is intraspecific competition?

competition between individuals of the same species

What happens to intraspecific competition as a population nears K?

higher intraspecific competition, there are more individuals and less resources

What is self-thinning?

only in plants; as density increases the biomass of trees decreases, this graph always has a -3/2 slope; we can’t have trees above this slope or else self-thinning occurs

What is the competitive exclusion principle?

states that no 2 species can coexist in exactly the same niche

What is interference competition?

competition in which direct interactions result in restricted access to a resource

What are the 3 types of interference competition?

allopathy, territoriality, and preemption

What is alleopathy?

type of interference competition where plants release poison

What is territoriality?

interference competition where there’s an establishment of an area by one or more organisms from which others are partially excluded; only in animals

What is preemption?

interference competition determined by who first finds and occupies a location, prevents others from using the space

What is interspecific competition?

competition in which individuals of one species limit resources available to another species; affects all species involved, some more than others, and may drive populations to extinction

What is a competition coefficient?

represents per capital effect on the growth of one species on another species; ⍺₁₂ indicates the effect of species 2 on the population growth rate of species 1

If ⍺ > 1 what does that indicate?

interspecific competition is greater than intraspecific competition

If ⍺ = 0 what does that indicate?

interspecific competition is absent

If ⍺ < 0 what does that indicate?

interspecific competition is less than intraspecific competition

If ⍺ = 1 what does that indicate?

interspecific competition is equal to intraspecific competition, species can coexist and are stable

What equation is dN₁/dt = r₁N₁ [1-(N₁+⍺₁₂N₂/K₁)] ?

interspecific competition equation for species 1

What equation is dN/dt = rN [1-(K-N/K)] ?

intraspecific competition equation

What is a zero growth isocline of population growth?

a line that describes a situation under which a population size will remain constant while in engaged in competition with another population

How do we create zero growth isoclines?

• plot the carrying capacity as the first dot

• then take the carrying capacity and divide it by the competition coefficient to get the second dot

• do this for both species