Chapter 9: Introduction to Population Ecology Flashcards
Distinguish between unitary and modular organisms and give examples of each.
Unitary: form and development are highly determinant, zygote develops into a recognizable form quickly (dogs, cats, humans)
Modular: development unpredictable and depend on environment, zygote develops into module (coral and other colonial animals)
How are animal population sizes estimated?
mark/recapture technique: take a random sample and mark them, later return and capture another sample and take note on which ones are marked
How are plant population sizes estimated?
sampling quadrants: selecting random plots of varying size and shape and make generalizations based on the information
Define random pattern of dispersion
if randomly distributed then distance between each individual is independent of the location of other individuals (RARE)
Define Contagious (clumped) pattern of dispersion.
Plots with greater number of individuals than expected, social groups or patches of resources
Define regular (uniform) pattern of dispersion
same number of individuals in plots, equally distanced; territorial or chemical barriers (plants)
What might a population in nature show a contagious pattern of dispersion?
social groups, ie: prairie dogs
What kinds of biotic interactions might a uniform pattern of dispersion suggest?
territorial animals
allelopathy: creation of chemical barriers around plants to prevent growth of others
What information is required to construct a dynamic (cohort) life table?
group of individuals born at the same time and followed until death, best type of life table because no assumptions are made
What information is required to construct a static life table?
age structure of a given population
Give four assumptions that are required for a static life table to be valid.
- each age class is sampled in proportion to it’s numbers in the population
- birth rates and death rates are constant
- population is stable, not increasing or decreasing
- survivors of the one-year age class were the survivors from the year before as if they all belonged to the same cohort
What kinds of information might you use to construct a life table for species such as annual plants and insects that do not have overlapping generations?
use stages of development instead of time intervals
Why is survivorship normally plotted on a semilogarithmic scale?
interested in per capita rates of change, not absolute
-nx values plotted on logarithmic scale while age (x) is plotted on an arithmetic scale
Describe a Type 1 survivorship curve.
low mortality through lifespan followed by a major decline later in life
-humans
Describe a Type 2 survivorship curve.
constant mortality
-birds, Connell’s barnacles
Describe a Type 3 survivorship curve.
high initial mortality followed b a period of much lower, relatively constant loss
-fish, marine invertebrates, oysters, clams
Why do population data typically result in a “J-shaped” mortality curve?
high mortality in juvenile phase, then mortality rate decreases to a minimum after juvenile phase and then rises again with increasing age
Why may it be preferable to use a mortality curve instead of a survivorship curve to track the fate of a population over time?
it is independent of the size of the younger age classes; it is more free from bias (less error)
How is net reproductive rate (Ro) defined?
the mean number of offspring produced by an individual during its life
What does it mean when Ro>1, Ro=1 or Ro<1?
Ro>1: population is increasing
Ro=1: population is exactly replacing itself
Ro<1: population is decreasing
What does Ro represent in a population with discrete (no-overlapping) generations?
- average number of offspring produced by an individual during its lifetime
- overall extent by which the population has increased or decreased over that time
What does Ro represent in a population with overlapping generations?
ONLY the average number of offspring produced by an individual during its lifetime
Why might it be preferable to express population growth rate as an exponential constant (r) rather than as a geometric constant (R)?
when ecologists are more interested in instantaneous rates of population change, or how much a population is changing at any particular moment in time rather than how much a population has changed over a time interval.
Give five factors that influence an organism’s intrinsic rate of population growth.
- death rate of an organism under ideal conditions
- fecundity: number of offspring produced by an organism over its lifetime
- length of organism’s reproductive lifespan and ability to conceive
- frequency of reproduction
- age of first reproduction
