Ch.53 Population Ecology Flashcards
Changes in population come from
Births, immigration
Deaths, emigration
A group of individuals of a single species living in the same general area. The boundaries are either natural or defined by an investigator.
Population
Density
the # of individuals per unit area/ volume
Dispersion
pattern of spacing among individuals within boundaries of the population.
Why do scientists use the mark-recapture method
It’s impossible/ impractical to count all the individuals
3 patterns of dispersion (most to least common)
Clumped
Uniform
Random
Clumped dispersion
most common. due to environments mating behavior, defense in numbers
Uniform dispersion
secretion of chemicals, germination, territoriality.
Random dispersion
least common. each individual is independent and occurs bc of the absence or strong attractions/repulsions
Demography
study of key characteristics of populations and how they change overtime
Life table
summarizes survival and reproductive rates of individuals in specific age groups in a population. Usually uses females. Presented in a chart/graph
-Age
-Number alive at start of yr
-Death rate
-Average number female offspring per female
Cohort
group of individuals of same age
Survivorship curve
plots of a proportion/ numbers in a cohort still alive at each age.
Type I curve
flat at the start reflecting low death rates and early to middle life drops steeply as death rates increase in elders. (mammals). Low mortality
Type II curve
Constant death rate
Type III curve
Contrasts I. drops sharply at the start and evens out. common in organisms that produce lots of offspring with little care. Survivors live longer
Reproductive rates
for sexual organisms measured as average number of female offspring produced by females in an age group
If a population ecologist can’t locate organisms themselves to estimate a population, what indicators might they use instead?
size, density, dispersion, age structure
Some organisms exhibit different dispersion patterns at different times of the year because
environmental conditions favor growth, germination, movement, and mating.
Exponential growth
rapid growth of the population where resources are plentiful
logistic growth
realistic/sustainable growth of population
What do ecologists know to be true about K?
-it’s the maximum population size a particular environment can carry
-K varies over space and time with abundance of limiting resources (crowding/resource limitation)
Delta=
change in time
N=
population size
t=
time interval
R
B-D
Per capita
contribution an average member of population makes to number of individuals added/subtracted from the population in time interval.
r
per capita change in population size that occurs at each instant time
Intrinsic rate of intrest
per capita rate at which an exponentially growing population increases in size at each instant time.
-J shaped curve
Density independent population
BR and DR that doesn’t change with population density.
-negative feedback loop; disease, competition, toxic waste. Birth and death rates not affected by population density
Density dependent population
Birth and death rates rise as population density increases.
ZPG =
high BR - high DR / low BR- low DR
Carrying capacity (K)
maximum population size that a particular environment can sustain. varies over space and time with abundance of resources. crowding and resource limitation has profound effects on population growth.
Logistic growth model
per capita rate of population growth approaches 0 as the population size nears K.
-Shaped curve (sigmoid)
-assumes that populations adjust instantly and approaches K smoothly
The study of population dynamics focuses on complex interactions that cause a variety in population size. What are examples of those interactions?
Abiotic and Biotic factors
Life history
traits that affect an organism’s schedule of reproduction and survival
-when reproduction begins, how often, how many offspring
Semel parity
reproduction in which an organism produces all of its offspring at once (big-bang reproduction)
Iteroparity
repeated reproduction
K -selection
selection for traits that are advantageous at high densities
r-selection
said to maximize r, intrinsic rate of increase and enviroments below k.
Metapopulations
A group of spatially separated populations of one species that interact through emigration and immigration.
-habitats can be suitable/ non suitable/ occupied/ non occupied. patches.
Population dynamics
Population fluctuations from year to year or place to place. Bust and boom cycles.
1. food shortage
2. predator-prey interactions
Demographic transition
High BR and DR to Low BR and DR. Associated with better health care and education.
Commonly graphed like pyramids
-K= 10 to 15 bil for humans
Age structure
relative number of individuals at each age in population. illuminates social conditions.
Ecological footprint
the aggregate land and water area required by each person, city, or nation, to produces all the resources it consumes and to absorb all the waste it generates. shows how close we are to K
