1. Ecology (BIO C322) Population Ecology

2. Population Group of organisms of same species occupying a particular space, Functioning as part of biotic community. Group attributes meaningful only at the population level. e.g. birth rate, death rate. Demography = Stastical study of human populations  birth, migration, aging, death.

3. Indices of Density Population density: Size of a population (number or biomass) w.r.t. a definite unit of space. e.g. 1 tree/m 2 Crude density: No. per unit of total space. Ecological density: No. per unit of habitat space. Relative abundance; may be time-relative. e.g. No. of birds seen per hr. Frequency of occurrence: % of sample plots occupied by a particular species.

4. Mark-recapture Method to estimate Population Density

5. Lincoln Index To estimate no. of organisms, X, of a species in a given area. X = Population estimate N 1 = No. of animals captured & marked in sample S 1 at time t 1 N 2 = No. of animals captured in sample S 2 at time t 2 M 2 = No. of marked animals found in sample S 2 at time t 2.  X / N 1 = N 2 / M 2

6. Quadrat or Transect Sampling Counting organisms of a single species in plots of transects.

7. Natality (Birth) Ability of a population to increase by reproduction; birth rate. Absolute or crude natality rate: No. of new individuals produced per unit time. Specific natality rate: No. of new individuals per unit time per unit population. Maximum natality: Theoretical maximum; under ideal conditions; no limiting factors. Ecological or realized natality: Under actual conditions (size and age composition & abiotic factors).

8. Mortality (Death) Absolute or crude death rate (deaths per unit time). Specific death rate (M). Minimum mortality: Under ideal conditions. Ecological or realized mortality. Survival rate = 1 - M

9. Life Table Table of mortality & survivorship schedules of a population based on an initial cohort. Study table 6.1 (TB): Life table for an Alaskan population of Dall mountain sheep.

10. Another example: Cohort of 530 grey squirrels (Sciurus carolinensis): Study in Virginia x (Age)nxnx l x = n x /n o d x = n x - n x+1 q x = d x /n x 0-153013710.70 1-21590.3790.50 2-3800.15320.40 3-4480.09270.55 4-5210.04160.75 5-650.0151

11. Mortality & Survivorship Curves Graphical representation of life table data. Mortality curve: q x (age-specific mortality rate) plotted on y-axis, age on x-axis. Survivorship curve: n x or l x plotted on y- axis (log 10 scale), age on x-axis. Mean life expectancy or mean duration of life: Age at which half the population is still surviving.

13. Effect of Density Shape of survivorship curve varies with density of population. Figure 6.4 (TB): Curves for two mule deer populations; Observations: Curve for denser population is more concave  Shorter life expectancy. Increased hunting pressure and intra- specific competition.

14. Age Structures / Pyramids Three major age groups in a population: pre-reproductive, reproductive & post- reproductive. Age pyramid: Oldest group at top. Age structure of different population types: –Expanding: rapidly growing population. –Stable –Diminishing

17. Species Differences in Age Structure Relative distribution of the ages varies among different populations. For humans, these ages are almost equal in length, about 1/3 of human life falling in each class. Insects: Long pre-rep periods, very short rep period and no post-rep period. For angiosperms (plants), the ratio of life span to pre-rep stage is 10:1.