population ecology - exam 4 Flashcards
population ecology
dynamics of species populations & how they interact w/ the environment
population
group of individuals of the same species that live in the same area
INTRAspecific interactions
interactions between members of the SAME species
same resources
same environmental factors
density
number of individuals per area
mass in a given volume
what is density limited by
resources
limiting agents - disease parasites, predators
dispersion
local densities differ – contrasting patterns of dispersion
clumped dispersion
individuals aggregated in patches
what does clumped dispersion result from
uneven distribution of resources
mating or social behaviors (hunting together)
uniform dispersion
individuals evenly spaced
what does uniform dispersion result from
aggressive interactions
severe competition for resources
random dispersion
no pattern seen
what does random dispersion result from
no special forces acting on spatial distribution of individuals in population
homogenous environment
population structure
make up of individuals in the population
sex ratio
age structure
sex ratio
males: #females
primary = conception
secondary = birth/hatching
tertiary = later stage of life
ratio can become more skewed
reproduction related stresses
reason for skewed 3rd sex ratio
ex - females not fighting, nesting females more vulnerable
dispersal
reason for skewed 3rd sex ratio
(leaving the nest) increases risk of predation in dispersing sex
intraspecific competition
reason for skewed 3rd sex ratio
dominance status
energetic requirements
intraspecific competition examples
migrating birds - males go first & take prime spots, females have to go farther
elk - males are bigger & more susceptible to food shortages & sink into snow
age structure
% of individuals in different ages or age groups in the population
can be used to predict future population growth/decline
population rates
growth & decline
survival patterns
fecundity
of offspring/time (per female)
generally limited by # of gametes (eggs)
survivorship
tracks changes in # of individuals in a cohort over time
type I survivorship curve
late loss
most deaths occur at limit of biological lifespan
humans, annual plants, sheep, elephants
type II survivorship curve
constant loss
individuals in all age categories have fairly uniform death rates
rodents, perennial plants, song birds
type III survivorship curve
early loss
death is prevalent for younger members & declines w/ age
sea turtles, trees, fish, internal parasites
life history traits
traits that affect an organism’s schedule of reproduction & survival
r & K strategists
r-strategist
many offspring
small offspring
no parental care
grow fast
reproduce young
type III
exponential growth rate
pyramid shaped age structure
K-strategist
few offspring
big offspring
lots of parental care
slow growth
delayed reproduction
type I
logistic population growth
columnar age structure
exponential growth
rate of population expansion under ideal conditions
abundant food
free to reproduce @ physiological capacity
exponential growth equation
dN/dt = rN
r = rate of increase
larger r = faster growth increase
r is small if…
high death rate
low birth rate
individuals not fecund or fertile
sex ratio skewed towards males
long generation time
density dependent pop limiting factors
food
space
disease
predation
territoriality
toxic wastes
density independent pop limiting factors
weather
disease
abiotic factors
not living
natural disasters
temp
soil
water
carrying capacity
K
maximum pop size that a particular environment can sustain
varies over space & time – changing w/ resources
logistic growth
idealized pop growth that is slowed pop limiting factors as pop size increases
logistic growth equation
dN/dt = rN(1-N/K)
