Ecology and Population Flashcards
Ecology
the study of the interactions between organisms and their environment.
Epidemiology
- branch of medicine
- that deals with the incidence
- distribution
- and possible control of
- diseases and other factors relating to health.
population
group of individuals
- of the same single species
- that simultaneously occupy the same general area
density of population
number of individuals per unit area
dispersion of population
the pattern of spacing between individuals within geographic boundaries.
what defines how populations are distributed?
resources
clumped dispersion
when individuals aggregate in patches
uniform dispersion
when individuals are evenly spaced.
random dispersion
the position of individuals is independent of the others.
demography
study of factors that affect the growth/ decline of populations
main types of graphs in demography
- life tables
- survivorship curves
life tables
age-specific summary
-of survival pattern of a population.
cohort
group of individuals of the same age
best way to construct a life table?
follow a cohort for their whole lives and document it
reproductive table
an age specific summary
-of reproductive rates of a population
why do demographers usually ignore males?
they can’t give rise to offspring
life history
the traits that affect an organism’s schedule of reproduction and survival. caused by natural selection and parallel environmental factors.
semelparity
when the organism produces large numbers of offspring during reproduction and then the individual dies afterwards.
example of semelparity
agave plant
iteroparity
have many reproductive episodes but only produce a few eggs during each one.
example of iteroparity
giraffes, humans
change in population size during a fixed time interval
number of births during time interval - number of deaths during time interval
N/t = B-D (the squares in this case are meant to be triangles that represent “change in”)
ZPG
Zero population growth i.e. Birth rate = death rate
Under what conditions does exponential growth in population usually occur?
Unnatural conditions eg. breeding programmes
How is population growth regulated?
carrying capacity
Carrying capacity
the maximum stable population size an environment can support
What does the logistic population growth model do?
takes into account population density and carrying capacity when calculating the rate of increase. K= carrying capacity
dN/dT= rmax N (K-N/K)
examples of when the logistic population growth model doesn’t apply
population of song sparrows
Density-dependent factors
increase their affect on a population as population density increases. (negative feedback) eg. death rate
Density-independent factors
are not affected by population density. No feedback to slow population growth
What causes negative feedback?
- limited resources leads to reduction in reproduction
- waste accumulation
- disease (spreads more rapidly in denser populations)
examples of erratic population fluctuation
male crabs
examples of “boom and bust cycles” (fluctuate greatly)
lynx, snowshoe hare
What are some problems facing large populations
- stress on renewable resources
- reduction of nonrenewable resources
- shortage of food
- increased energy requirements
When did the rate of growth start slowing down and why?
1960’s
-due to diseases such as AIDS and voluntary population control
Why is human population said to be heterogeneous?
Because it is made of smaller populations, each with different characteristics
What must be ensured to have population stability?
ZPG
high birth rates - high death rates = ZPG
low birth rates - low death rates = ZPG
Demographic transition
The movement from high birth rates- high death rates to low birth rates-low death rates (i.e. each time is ZPG)
What is one of the biggest things that leads to demographic transition?
-Reduced family size
due to contraception, social change (delaying having children), family planning etc.
What is age structure and what is the benefit of it?
- the relative number of individuals of each age.
- it can predict future growth trends eg. possible diseases, should governments be increasing funding for nursing homes etc.
What is the population of the earth predicted to be by 2050?
7.3 to 10.7 billion
Ecological Footprint
a measure of the demand on and supply of nature.
What are the 6 types of ecologically productive areas that are used when calculating the ecological footprint?
PLOBFF
- Pasture
- Land used for growing crops
- Ocean
- Built up land
- Forestry
- Fossil energy land
