10/11 quiz Flashcards
what is the purpose of survivorship curves?
to assess patterns of survival in a population
what group of individuals does a survivorship curve follow?
a single generation - a cohort
what is plotted on survivorship curves?
the number of individuals still alive at that stage
type I curve
most individuals survive until old age
typically produce few offspring and have parental care
why do type I curves have low offspring mortality?
able to have parental care bc most individuals live until old age
type II survivorship curve
individuals have a constant chance of being killed at any point in life
small birds and mammals that are killed heavily by predation
type III curve
individuals have a low chance of survival when young, but survive well if they can make it to adulthood
typically lots of offspring but no parental care
what are factors that can impact survivorship curves?
habitat quality and sex
what’s something to note about survivorship curves?
the y-axis is logarithmic
how can habitat quality impact survivorship?
food quality and predation
how can sex impact survivorship?
differences by sex, such as competition for mates
what are dispersion patterns?
patterns of spacing among individuals
what are the three types of dispersion patterns?
clumped, uniform, and random
what influences cause clumped dispersion?
positive biotic interactions (btwn individuals)
common resources
what influences cause uniform dispersion?
negative biotic interactions (competition and territoriality)
what influences cause random dispersion?
absence of biotic interactions
not very common
example of clumped dispersion
penguins
to conserve heat and to be social
example of uniform dispersal
shrubs
example of random dispersion
dandelions in lawn
plenty of resources and can thrive anywhere
census
all individuals in population counted
when do censuses work best?
when individuals are large and easy to count
why are censuses inherently inaccurate in the US?
its too large of a population and territory
what does population estimation work well with?
sessile species using quadrats
can leave permanent markers to come back to
what does mark-and-recapturing do?
allow for sampling of mobile species
how do mark-and-recapture samplings work?
mobile species are marked with a band, tattoo, or radiotracked
what mathematical model does mark-recapture sampling use?
Lincoln Index
N = nM/R
what do the variables in the lincoln index mean?
N : estimated population size
n : total number of individuals captured in first census
M : number of individuals captured during second census
/
R : number of marked individuals recaptured during second census
what are the assumptions of the lincoln index?
equal chance of recapture for all individuals in population
ratio between marked and unmarked individuals remains constant
individuals don’t lose their mark
population is closed
what is meant by ratio staying constant with respect to marked and unmarked individuals?
we are neglecting death and predation
what is meant by all members of pop having an equal chance of recapture?
no one is “trap shy” or “trap happy”
what is meant by the population being closed?
no immigration or emigration
what are the factors that influence population size?
births, death, immigration, emigration
what is the first mathematical model for population growth?
N(t+1) = N + (births - deaths) + (immigration - emigration) all at time t
assumptions for the first population growth model
all individuals are identical (no age, genetic, or evolutionary differences)
birth and death rates are constant
no immigration or emigration
habitat is perfectly uniform
what are the modeling options if we are working with non-limiting resources?
if discrete generations -> geometric growth
is overlapping generations -> exponential growth
what is the modeling option if we are working with limiting resources?
logistic growth
how do populations grow?
in proportion to their size
what is the geometric growth model used for?
populations that vary due to seasonal changes in birth and death rates
many birds and mammals
what is lambda in geometric growth?
population growth rate constant
what value of lambda makes a population INCREASE?
greater than one
what value of lambda makes a population DECREASE?
less than one
what value of lambda makes a population STABLE?
equal to one
example of organism with discrete generations
emerald ash borer
new generation of adults each spring, all adults die that summer
no generational overlap
how do we calculation geometric growth for more than a year of change?
make lambda to the power of the year
5 year change -> N(0) * lambda^5
what are conditions in which geometric and exponential growth can occur?
when a new habitat or geographic range are established
exploiting temporarily favorable conditions
recovery after protection
loss of predator or competition
example of establishing a new habitat
killer bees on new continent
virtually unlimited resources
example of exploitation of temporarily favorable conditions
dandelion in empty lawn
can reproduce anywhere and has lots of resources
example of recovery following protection
whooping cranes
n = 22 -> 505
what are examples of organisms that use exponential growth models?
bacteria, many pest species, and humans
what does dN/dt mean?
instantaneous population growth rate
change in population over change in time
what does r mean?
per capita population growth rate
constant
what does r numerically represent?
birth rate - death rate
= ln(lambda)
what is r when population is increasing?
greater than zero
what is r when population is decreasing?
less than zero
what is r when population is stable?
equal to zero
how can we use the exponential growth model to calculation population size?
integrate growth over time
what is population growth affected by?
biotic and abiotic factors
what are biotic factors that can affect population growth?
predation, food supply, competition, parasites, pathogens, and mutualists
what is a bottom-up biotic factor?
regulating food chain from lower trophic levels
what is a top-down biotic factor?
regulating food chain from upper, predation, trophic levels
example of bottom-up biotic factor
El Nino warm waters flowing towards the Galapagos
decline in marine food base -> decline in penguin population
example of top-down biotic factor
decrease in marine predators -> increase in foraging fish -> decrease in zoo plankton -> increase in phytoplankton
what is the pattern of bottom-up biotic factors?
layers of the food chain experience the same direction of change
what is the pattern of top-down biotic factors?
alternating directions of the food chain layers
what regulates population growth rates?
biotic and abiotic factors
density independent and dependent factors
what are density-independent factors?
events that affect the same proportion of the population regardless of population density
regulates r but not N
often unpredictable changes
what are examples of density-independent factors?
hurricanes, flooding, unpredictable changes in temp, and volcanoes
what’s an example of a density independent population regulation event?
all the monarchs freezing in Mexico due to an unexpected change in temperature
population change wouldn’t impact result here
what are density-dependent factors related to?
darwin’s theory of natural selection
how are density dependent factors related to another phenomena?
darwin’s theory of natural selection:
each individual has a high potential reproductive rate
a lack of resources will eventually limit the population
intense competition and differences among individuals become an important source for natural selection
birth and death rates change as a function of ___?
population density
effectiveness increases as population size increases
what are some density-dependent factors that might affect population growth rates?
crowding
competition for food or sunlight
pathogen attack
pollinator attraction
what will happen to birth/death rates and dispersal as densities increase?
birth decreases
death and dispersal increase
how can hunting affect density and population growth rate?
kill a lot of animals, but then there’s a lot of resources for the remaining animals to thrive off of
what do density-dependent factors do for the population?
serve as a negative feedback system
how do density dependent factors serve as a negative feedback system?
rate of growth slows as population density increases
how can we identify a density-dependent factor?
look for correlation between mortality or reproduction and population density
there will often be a time lag
what is carrying capacity?
an equilibrium population size, where populations should stabilize
what do logistic growth models show?
populations growing rapidly at first but then slowing as resources dwindle
population growth will hit zero and population size with stabilize
looks like an s-shaped curve
what population size do logistic growth models stabilize at?
carrying capacity, K
what is the logistic equation a modification of?
exponential growth equation
adds a term to reflect changes in population size as K is approached
what happens when N > K?
dN/dt is negative
population declines
what happens when N < K?
dN/dt is positive and population grows
what happens when N = K?
dN/dt = 0
population is stable
what do density-independent factors do to the population?
represent distrubance
potentially prevent population from reaching K because of unexpected events
we can predict population ___ and ___ using ___ ___
size and growth using mathematical models
stable populations fluctuate within ___ ___
narrow limits
what factors can impact population stability patterns?
density dependent and independent
can populations be stable if not a equilibrium?
yes!
but generally are close to it
what does the modification to the logistic growth model allow for?
consideration of unused opportunities for population growth based on carrying capacity
for multiple populations experiencing the same density-independent occurrence (hurricane, tornado, etc.), what would we expect the graphs to look like?
similar because the same effect will be happening across the area
for multiple populations experiencing the density-dependent occurrences, what would we expect the graphs to look like?
fluctuations between populations because they will tend to do different things
what causes populations to cycle?
regular environmental changes
intrinsic dynamics
interactions with predators or disease
what is an example of a regular environmental change that causes population cycles?
El Nino events -> decrease in resources -> density dependent
what are the types of intrinsic dynamics?
no oscillation, damped oscillation, and limit cycle
what are intrinsic dynamics?
a type of fluctuation in population size due to time delays that depend on population growth
what do no oscillation graphs look like?
normal logistic growth model, s-shaped curve
what is r when there is no oscillation?
r < 1
what are damped oscillations?
populations getting progressively closer to K
start big but bounce around getting closer
what is r in damped oscillation?
1 < r < 2
what are limit cycles?
population numbers alternate between high and low values until the population goes extinct from hitting 0
what is r in limit cycles?
r > 2
what does self regulation require?
organisms to have internal mechanisms to respond to population density
what is an example of an internal mechanism for population density control?
stress hormones to decrease reproduction or increase mortality
what is an example of population cycles due to predation/disease?
red grouse
parasite that reached peak-build-up every four years and would dramatically impact red grouse populations
how do vaccines use host-parasite relationships?
treat enough people to reduce parasite/pathogen burden to prevent significant population declines
environmental variations tend to be ___, while fluctuations in many populations are ___
random and non-random
growth rates are ___
density-dependent
regulatory factors vary over ___
space
populations are spatial mosaics because they have different ___ ___ in different ___
regulatory processes in different areas
life history
organism’s lifetime pattern of growth, reproduction, and death
what is the life history strategy?
patterns in growth and development
life span
timing and quantity of repoduction
example of long life - few offspring organism
rhinos
example of short life - many offspring organism
mosquitoes
what can be identified by an organism’s life history?
mode and age of maturity for reproduction
size and number of offspring
parental investment and parity
life span
what is parity?
number of reproductive events
why don’t we evolve life history to maximize fitness?
there are tradeoffs due to limited resources
“problem of allocation”
there is an ___ energetic investment for a particular life history component
optimal
investing beyond optimal energy for a particular fitness components can…
overall reduce fitness
limited energy to other important functions
what do high mortality rate adults favor?
current fecundity
breed now, could die tomorrow
what do long lifespan adults favor?
delayed reproduction
save energy, you have time
example of high mortality rate organism
swainson’s thrush
lifespan = 3-4 yrs
produces 1-3 broods per year
example of long lifespan organism
leach’s storm-petrel
lifespan = 30-40 yrs
produce 1 young per year
benefits of early breeding
increase fecundity
costs of early breeding
reduced survival to older age bc of energy allocation
reduce fecundity at older age
indeterminate growth
organisms that don’t have a typical adult size
fish, some plants, some invertebrates
fecundity is related to ___ ___
body size
increased fecundity in one year …
reduces growth and future fecundity
example of optimal allocation
bird having 7 eggs per brood
5 -> one dominates and kills other chicks
9 -> parents can’t properly care for young
what are the three key developmental features of life cycles?
embryo -> adult
presence of dormancy stages during development
development and constancy of organism’s sex
direct development
adult develops from fertilized egg
no larval stage
indirect/metamorphic development
larval stage present
two radically different stages
example of direct development
dolphins or humans
example of indirect development
frogs or butterflies
costs of metamorphosis
significant energy expenditure
vulnerability to predation at certain stages
advantages of metamorphosis
specialization on different functions at different life stages
use of different ecological niches
reduced competition among larvae and adults
neoteny
adults retain larval forms but can reproduce sexually
more common in extreme environments
dormancy in development
flower in desert
resist harsh environmental conditions
seeds, spores, cysts
asexual reproduction
progeny are genetically identical to e/o and parent
clones
occurs in plants and some animals (corals, insects, fisk, snakes, birds)
parthenogenesis
producing eggs with two sets of chromosomes
all progeny are female
can produce with males, but can due in absence as well
what organisms can do parthenogenesis?
some insects, snails, reptiles, …
