exam 3 ppt 4 Flashcards
who was Thomas Malthus?
he was a British scholar, 1790; he influenced Darwin - resource limitation applies to all species
what is the fundamental unit of evolution?
populations
definition of populations
include all individuals of a species that live and reproduce in a certain place
definition of population ecology
the study of how and why a population changes over time
what are populations described in terms of?
size (N), geographic range, and spatial distribution (density)
can range be considered on different scales?
yes- can have local range, regional range, and global range
how would you measure the size of a population?
census, sampling
definition of census
a way to measure populations; count every individual; organisms must be easy to observe, not too numerous, and occur in an easily defined area
what are the requirements for taking a census?
organisms must be easy to observe, not too numerous, and occur in an easily defined area
different sections of sampling
quadrats, mark-and-recapture
definition of quadrats (sampling)
sessile of stationary organisms (ex: plants)
exp of an organism sampled by quadrats
plants
definition of mark-and-recapture (sampling)
mobile organisms
what type of distribution tells us more about a population?
spatial distribution
types of spatial distributions (listed)
uniform, random, clumped
what does uniform distribution look like?
all evenly distributed
what does random distribution look like?
some clumped, some fary away, randomly placed
what does clumped distribution look like?
all clumped together in a big group
exp of a clumped distribution
a herd of elephants
can spatial distribution change over time?
yes
exp of how spatial distribution changes over time in shrubs
small shrubs establish in high densities and produce a clumped distribution; mortality as the shrubs grow reduces clumping and produces a random distribution among medium shrubs; competition enforces a regular distribution among large shrubs
definition of demography
the statistical study of population dynamics over time
what things contribute to population decrease?
mortality (death) and emigration
definition of emigration
organisms leaving an area
what things contribute to population increase?
birth and immigration
definition of immigration
organisms coming into an area
what can population growth be?
population growth can be exponential or logistic
what is logistic growth limited by?
logistic growth is limited by K (carrying capacity)
is exponential growth limited?
no, it has maximum r = rate of growth
what do life tables provide?
life tables provide important information about the life history of a population, and can help predict the future of the population
R0 > 1=
population is growing
R0 < 1=
population is shrinking
R0 = 1=
population is stable
definition of fecundity
the reproductive capacity of an individual
do survivorship curves vary among organisms?
yes
definition of type I survivorship curve
survivorship throughout life is high, most individuals approach the maximum life span of the species (humans)
are organisms with type I survivorship r or K strategists?
K-strategists
definition of type II survivorship curve
most individuals experience relatively constant survivorship over lifetime; doesn’t have a specific life history table connected to it, in the middle
exp of an organism with type II survivorship curve
songbirds
definition of type III survivorship curve
high death rates early in life, high survivorship after maturity
are organisms with type III survivorship curves r or K strategists?
r-strategists
exp of an organism with type III survivorship curve
many plants
exp of an organism with type I survivorship curve
humans
what do survivorship curves graph?
they graph the number of individuals surviving at each age vs. time
life history strategies
birth -> growth -> reproduce -> death
why do fitness trade-offs occur?
they occur because every individual has a limited amount of time and energy; must choose between: reproduction and lifespan, and number of offspring and investment per offspring
regarding fitness trade-offs, what must you choose between?
1) reproduction and lifespan, 2) number of offspring and investment per offspring
definition of r-selected species
adapt to maximum reproductive rate
definition of K-selected species
adapt to living at carrying capacity (K) of environment, invest more energy in fewer offspring
do r-strategists have high or low fecundity?
high
do r-strategists have high or low survivorship?
low
do K-strategists have high or low fecundity?
low
do K-strategists have high or low survivorship?
high
r-selected are adapted to…
maximize r
K-selected adapted to thrive at…
K
can r-selected be advantageous in unstable environments?
yes
do r-strategists have many or few offspring?
many
do r-strategists have small or large offspring?
small
do K-strategists have many or few offspring?
few
do K-strategists have small or large offspring?
large
characteristics of r-strategists
many offspring, small offspring, early maturity,small body size, low disease resistance, low predator resistance, short life span
characteristics of K-strategists
few offspring, large offspring, late maturity, large body size, high disease resistance, high predator resistance, long life span
