Ecology Test 3

Population Variables
Abundance, Density, Spacial Distribution, Movement, Age Structure, Sex Ratio, Mortality, and Natality
Modular Organism
Grows by repeated iteration of parts (leaves, shoots, branches, polyps).
Includes colonial and clonal organisms (plants, corals, sponges). Modules may separate and become physiologically independent.
Genet
Individual from zygote
Ramet
Individual arising asexually
Clone
Group of ramets that arise from same genet
Unitary Organisms
Arise from a zygote,
grow by determinate pathway,
includes vertebrates, arthropods, some plants
Metapopulation
Assemblage of spatially distinct subpopulations. Landscapes are patchy with subpopulations distributed among patches.
Original Metapopulation Model
Patches of habitat in landscape, some patches occupied while others vacant. mortality/natality more important than dispersal
Mainland-Island Model
Landscape has different size patches. Mainland supports large core populations and resistant to extinction. Island patches are small and more prone to extinction. Core colonists recolonize satellites, results in repeating extinction-colonization cycle
Source-Sink Model
Patches differ in quality. Source patches have high quality, support positive growth, and have source the colonists to sink patches. Sink patches are poor quality and have negative growth. Sink patches will go extinct without new colonists.
Crude Density
Number of animals in a population per area measured. (ex. whitetail deer per sq. mile)
Ecological Density
Number of individuals per usable habitat. Difficult to measure and is seldom used. (ex. quail per mile of hedgerow).
Patterns of Spatial Dispersion
Random, Clumped/Aggregated, Uniform/Regular
Random Spatial Dispersion
Position of individuals is unrelated. Caused by lack of interactions between individuals and/or resources randomly distributes.
Clumped/Aggregated Spatial Dispersion
Positions of individuals positively related (clumps). Caused by attraction between individuals and/or clumped resources
Problem of Scale on Spatial Dispersion
Different patterns emerge with change in observation scale. Multiple patterns means multiple processes
Passive Dispersal
Uses wind, water, gravity, or animals. Commonly used by plants, fungi, plankton, some animals. Distance traveled is relatively short.
Active Dispersal
Occurs among motile organisms. Natal dispersal involves dispersal of offspring while breeding dispersal involves movement to find breeding site.
Migration
Mass movement of animals in response to changing environment. Distance traveled can be feet or thousands of miles. Timed with regular temporal cycles (tidal, seasonal, etc).
Ways of Categorizing Age Classes
Time intervals/Age (days, months, years), Life History Stages (ex. egg, larva pupa) (pre-reproductive, reproductive, post-reproductive are also examples). Size classes (seedling, sapling, pole)
For stable mammal and bird populations, what is the rough ratio of young to adults?
2:1
Primary Sex Ratio
Ratio at fertilization. Usually 1:1
Secondary Sex Ratio
Ratio at birth. Often near 1:1. Sometimes skewed-usually toward males.
Tertiary Sex Ratio
Ratio at sexual maturity, often skewed: birds towards males, mammals towards females.
Quaternary Sex Ratio
Ratio among post reproductive individuals. Typically skewed toward females.
Ways of Measuring Death Rate
Mortality (number of deaths during a time period), Survivorship (number of survivors over a time period), Life expectancty (life remaining for individuals of a given age)
Life Table Construction
Lx is the number surviving to the beginning of the age class.
Nx is the number surviving to start of age class for cohort of 1000.
dx is the number dying during an age class for a cohort of 1000.
qx is the mortality rate for an age interval.
For Fecundity Schedule: add mx (average number of births per survivor during the age class), and add Lx*mx (average number of births during the age interval for the original cohort). Maternity is births divided by survivors.
Survivorship Curves
Type 1 – low mortality in the young age class, increasing mortality with old age (large vertebrates).
Type II – Constant mortality rate for all ages (many birds).
Type III – High mortality rate in younger age classes and decreasing with old age.
Ways of Measuring Birth Rate
Natality rate – Number of births during a time period.
Physiological Natality – Maximum possible offspring per individual for a time period.
Realized Natality – Actual number of successful births over a time period.
Net Reproductive Rate (R0)
R0= ?(Lx*mx) Expressed as average number of offspring per individual during their lifetime, if R0 is 1 the population is stable, greater than 1 its growing, less than 1 its shrinking
Finite Rate of Increase (?)
?= Nt+1/Nt If ? is 1 the population is stable, greater than 1 its growing, less than 1 its shrinking
Per Capita Rate of Increase (r)
Average change per individual for an entire population.
Estimated as r=lnR0/Tt
r=0 stable, r greater growing, r less shrinking
Mean Cohort Generation Time (Tc)
Tc= ?(Lx*mx)/ R0