Population Ecology Flashcards
ecology
study of how living organisms and the physical environment interact
Biotic factor
interactions among organisms
Abiotic factors-
interactions between organisms and the non living environment
examples of abiotic factors
Precipitation
Temperature
Wind
Population
group of individuals of same species living in
the same area
Community
groups of populations of diff species living in same area
Ecosystem
interrelations between organisms in a community and
their physical environment
Biosphere
all regions of the earth that contain living things
habitat
place where an organism lives (Includes organisms as well as physical/ chemical characteristics)
Niche
all biotic and abiotic resources in an environment
used by an organism–When an organism is in a niche, certain resources are consumed
or certain qualities of environment are changed by the organism
Population ecology considers….
considers both the
number of individuals of a species and dynamics of population
Population size is measured by ….
population density
population density
# of individuals of a species per unit of area or volume (varies from season to season)
delta
change in
rMax
ideal r/max per capita growth rate of population
rate equation
dY/dT
Population growth
dN/dt=B-D
exponential growth
dN/dt=rMaxNd
logistic growth
dN/dt=rMaxN((k-N)/k)
dY
amount of change
t
time
B
birth rate
D
death rate
N
population size
K
carrying capacity
Increase in pop size
births and immigration
decrease in pop size
deaths and emigration
Birth rate, or B
(“natality”)- average per capita (rates per individual)
birth rate –b/N
Death rate, or D
(“mortality”)- average per capita death rate–d/N
r expressed in
decimal
r
B-D
If B is greater than D
r is positive and the population is increasing
If B is less than D
r is negative and the population is decreasing
When B and D are equal
r is 0 and the population is constant
What is it called when the population is constant?
0 population growth
intrinsic rate of increase (rmax)
The maximum rate at which a population of a given species could increase
under ideal conditions (when resources are abundant and population density
is low)
large v small species intrinsic rate
large-Smaller, small-larger (bacteria),
Under optimal conditions, the reproductive rate of a population would have
….
exponential growth (j shaped curve)
why can’t organisms reproduce indefinitely at their intrinsic rate of
increase?
environment sets limits
ex of environmental limits
food, water, shelter, competition
Over time, rate of population growth may decrease to nearly zero-
population levels out when
….
environmental limits reached
Carrying capacity (K)
represents the largest population that can be
maintained for an indefinite period by a
particular environment
When does K change?
in response to environmental changes- ex- if there is a drought, carrying capacity for animals in the area decrease; if abundance of food, it’ll increase
logistic population growth
realized population growth–Curve of graph is an S-curve- When N is small, rate of population growth higher; As N reaches K, growth rate declines
when is pop growth rate highest
halfK?
population crash
abrupt decline
population cycles at k
Populations rarely stabilize at K- may temporarily rise above K, then drop down to or below K
what happens if a population overshoots K
population crash
Density-dependent factors
change in population density alters how an
environmental factor affects population
ex of density dependent factor
predation, disease, competition
which factor has less of an effect on a small population as compared to a large one
density dependent factor
Density-independent factors
environmental factors, usually abiotic, that
affect the size of population-
irrespective of density
ex of DI factors
random weather events such as frost, blizzard, hurricane
Life history traits
ways in which a species reproduces and survives
r- selected species-
traits that contribute to high population growth rate, reproduce quickly at their r
traits of r selected species
Small body size, short life span, no parental care
two extremes of life history traits
r selected and k selected
nickname r selected species
Called opportunist species- quickly inhabit an area, reproduce, die
Ex r selected species
Ex- weeds, mosquitoes
K- selected species-
traits that allow the population to function best at the K
traits of k selected species
Long life spans with slow development, late reproduction, large
body size, low reproductive rate, parental care
Found in constant stable environments
ex k selected species
humans, redwood trees, owls
Life tables-
show mortality and survival data of a population at different
times during their lifetime
Type I + ex
young have high probability of surviving, but with increasing
age, probability of surviving
decreases more rapidly ex-humans
Type II + ex
probability of death is equally likely across all age groups,
resulting in linear decline of survivorship
Ex- some lizards and rodents
Type III + ex
probability of mortality is highest early in life, and
probability of survival increases with increasing ages
Oysters- have free swimming larvae that are easily eaten
human population prediction, current
currently J with a slight dip for the plague –Even though population is increasing, the world growth rate is slowly
declining- predicted that the point of zero population growth (r= 0) will
occur toward the end of the 21st century
Age structure
number and proportion of people at each age in a
population
Age structure diagram
shows number of males and females at each
age, from birth to death
countries w high birth rate diagrams
Countries with high birth rates have pyramid-shaped diagram,
meaning that the probability of
future growth is great
stable population diagrams
tiers of equal width
shrinking population diagram
Shrinking population has prereproductive group smaller than
postreproductive group
do all countries have same growth rate
no
