Understanding Quantitative Data Collection in Ecology
Quantitative data collection in the ecology of a habitat, community, or town involves interpreting collected information to draw conclusions.
Population statistics encompass all the data from which we wish to draw conclusions.
Statistical sample: A statistical sample is a randomly selected subset of the statistical population.
Statistics can be divided into descriptive analysis and statistical inference.
Descriptive analysis: This involves comments, graphics, tabular data, or numerical data that allow us to sort the data in order to draw conclusions.
Statistical inference refers to specific procedures.
Central Tendency Measures
Mean: Defined as the sum of all values divided by the number of elements.
Median: The figure representing the number that divides the data into two equal parts.
Measures of Dispersion or Variability
These measures show the variability of a distribution. These data indicate the error between the numbers with respect to the arithmetic mean.
A) Range: The difference between the smallest and highest values in a set of observations.
B) Variance: The relationship between the sum of the squares of the observations and the degrees of freedom accordingly.
C) Standard Deviation: A measure of dispersion equal to the square root of the variance.
D) Standard Error: A function of standard deviation and sample size.
E) Coefficient of Variation: The standard deviation expressed as a percentage of the mean.
F) Coefficient of Dispersion: The relationship between the variance and the mean of the same distribution.
Continuous Data: Decimal numbers.
Discrete Data: Integers.
Population Demographics
Population: A large organization of individuals, a group formed by members of the same species living together in the same region at the same time.
Primary Demographic Parameters
Birth Rate: The ratio between the number of individuals born in a time unit within the population and the size of the population.
Mortality Rate: The ratio between the number of individuals who die in a time unit within the population and the size of the population.
Immigration: The arrival of individuals of the same species to the population. Measured by the immigration rate, which is the ratio of individuals arriving in a unit of time and the size of the population.
Emigration: The departure of individuals from the population to elsewhere. Measured by the emigration rate, which is the ratio of migrant individuals in a unit of time and population size.
(Births + Immigration) > (Mortality + Emigration) = Population increases, expanding its growth, represented with a + sign. Otherwise, the population will decrease over time (regression), and growth is represented with a – sign.
Demographic Aspects
Density: The number of individuals of a species per unit area or volume at any given time.
Spatial Distribution: The way organisms in a population are located in space. There are three types of distribution:
- Random: No regular pattern or affinity whatsoever.
- Uniform: Occurs when animals maximize the distance between their neighbors, often taking place when there is strong competition between individuals.
To determine the type of distribution, it is necessary to know the Poisson model, variance-mean ratio, and Morisita index.
Other Factors
Height, biomass, age, and growth.