bio 150 Flashcards
Group of individuals belonging to the same species occupying the same space at the same time
Why do populations grow and decline?
What regulates population size?
POPULATION
2 POPULATION CHARACTERISTICS
SIZE
DENSITY
total num of indiv in a population
SIZE
Health of a population
How______ is the population?
How_____ is the population growing?
LARGE ; FAST
Size of a population in relation to a DEFINITE UNIT OF SPACE; num of indivs of the same species per unit area
DENSITY
either in a unit of AREA / VOLUME
Space
How dense is the population?
Crowding
4 Measure of ABUNDANCE
BASAL AREA
BIOMASS
FREQUENCY
COVER
Total cross-section area of TREE TRUNKS; used by forest ecologist
BASAL AREA
Mass or weight of LIVING TISSUE
BIOMASS
The number of times PLANT species OCCURS i a GIVEN NUMBER OF QUADRANTS; usually expressed as percentage
FREQUENCY
Percentage of GROUND SURFACE COVERED as determined by the projection of areal parts
COVER
COMMERCIAL CATCH PER VOLUME of water or CAST OF NET of known area / volume (FISHERIES)
Population density: SPECIAL GROUPS
4 Methods for estimating population densities
TRANSECT-QUADRAT SAMPLING
PLOTLESS METHODS / point quarter method
IMPORTANCE PERCENTAGE VALUE
LINCOLN-PETERSEN INDEX / capture mark recapture
Counting or organisms of a single species in PLOTS or TRANSECTS of appropriate size & number
- Body size (range) of target groups
- Behavior (obvious/cryptic etc)
- Moile, sessile;weak-/strong-flying etc
TRANSECT-QUADRAT SAMPLING
- Objective: get an ESTIMATE of the DENSITY of the AREA SAMPLE
- Applicable to a wide variety of TERRESTRIAL & AQUATIC SPECIES in environments ranging from forests to the bottom of the sea
- EXAMPLE:
bird & butterfly transect – 2 km
Ant transect – 180-250 m
Weed sampling – 1 sq m quadrat
Forest – 1 sq km plot
TRANSECT-QUADRAT SAMPLING
Random points (0 dimensional method)
Applicable to sessile organisms (trees)
PLOTLESS METHODS / point quarter method
- Usually faster (especially in sparse communities)
- Requires less equipment - just need a way to measure distance (e.g., metervstick, tape measure, or laser range finder)
- Does not require selection or adjustment in quadrat size
PLOTLESS METHODS / point quarter method
3 types of PLOTLESS METHODS / point quarter method
POINT CENTER QUARTER
NEAREST NEIGHBOR
CLOSEST INDIVIDUAL
- series of random points
- Distance to nearest individual is measured in each of 4QUARTERS at each point along this series of random points
POINT CENTER QUARTER
- distance from a selected plant to its nearest plant (neighbor) is measured.
- Choose a referent plant - (usually the closest individual to a selected point.)
- Identify the plant closest to the referent plant and measure the distance between these two plants.
NEAREST NEIGHBOR
- The distance from a sample point to the closest individual is measured.
- Choose a series of points in the sample area
- Measure the distance to the closest plant of interest
CLOSEST INDIVIDUAL
- random samples of the population are captured and these individuals are marked and then released to mingle with the general population
- the population is resampled after enough time to allow complete remixing of the marked individuals
- Assumes that the proportion of marked animals in the second sample is the same as the proportion of marked animals to non-marked within the whole population
LINCOLN-PETERSEN INDEX / capture mark recapture
3 ASSUMPTIONS IN LINCOLN-PETERSEN INDEX / capture mark recapture
- Population is closed (births, deaths, emigration, and immigration are negligible)
- all individuals have the same probability of capture and recapture
- marked animals are randomly distributed in the population at the time of recapture
