Population Growth and Regulation Flashcards
demography
the study of the structure and growth of populations
2 models of population growth
geometric and exponential
geometric growth model
has discrete time intervals
- seasonal patterns of reproduction
exponential growth
has time treated as continuous
-species overlapping generations with year round reproduction (humans)
-smooth curve
growth rate
the number of new individuals produced in a given amount of time minus the number of individuals that die
intrinsic growth rate (r)
the highest possible per capita growth rate for a population
is density independent growth realistic
not always
density dependent
factors that affect population size in relation to the population’s density
negative density dependence
when the rate of population growth decreases as population density increases
- most commonly limiting resources (food, nesting sites, space)
self-thinning curve
a graphical relationship that shows how decreases in population density over time lead to increases in the size of each individual in the population
-often has a slope of -3/2
positive density dependence
when the rate of population growth increases as population density increases
- often known as inverse density dependence of Allee effect
-often occur when population densities are very low which makes it hard to find mates
- low densities can also lead to harmful effects such as inbreeding and a higher predation risk
carrying capacity (K)
the maximum population size that can be supported by the environment
logistic growth model
describes slowing growth of populations at high densities
S-shaped curve
the shape of the curve when a population is graphed over time using the logistic growth model
inflection point
the point on a sigmoidal growth curve at which the population has its highest growth rate
age structure
the proportion of individuals that occurs in different age classes in a population
age structure pyramids with broad bases indicate
a growing population
age structure pyramids with narrow bases indicate
a declining population
life tables
summary of class specific survival and fecundity
-model population growth and dynamics
stable age distribution
when the age structure of a population does not change over time
-occurs when survival and fecundity of each age class stays constant over time
type 1 survivorship curve
depicts a population that experiences low mortality early in life and high morality later in life
-bears, humans, elephants, and whales
type 2 survivorship curve
depicts a population that experiences constant mortality throughout its life span
-squirrels and corals
type 3 survivorship curve
depicts a population with high mortality early in life and high survival later in life
-weeds, fish, alligators
net reproductive rate (R0)
the total number of female offspring that we expect an average female to produce over the course of her life
generation time (T)
the average time between the birth of an individual and the birth of its offspring
cohort life table
a life table that follows a group of individuals born at the same time from birth to death of the last individual
-can be difficult to separate the effects of age and the environment
static life table
a life table that quantifies the survival and fecundity of all individuals in a population during a single time intervals
-used for highly mobile organisms and species with long life spans
