Part Three III › Division V V › Section 352 352

Biological Populations and Communities

Subject Outline

ABiological populations
- 1The study of populations [see 10/34.B.4.]
- 2The measurable characteristics of biological populations
  - aAge, sex, and genetic differences and their distribution
  - bNumbers and density: the effects of natality and mortality, the reproductive rate and death rate
- 3Growth of populations: growth form and carrying capacity
- 4Fluctuations in stable populations: variations in population size
- 5Movements: migration; emigration; dispersion; dispersal; the influence of topographical, climatic, and biological barriers
- 6Interactions of populations [see B., below]
- 7Factors affecting the structure of human populations [see 524.A.]
BBiotic interactions
- 1Intraspecific interactions: positive and negative interactions of individuals within a species
- 2Interspecific interactions: interactions among members of different species
  - aThe range of interspecies associations
  - bNegative interactions, in which one or both populations are harmed: consumption, parasitic interactions, amensalism and antagonism
  - cPositive interactions, in which one or both populations are benefited: commensalism, mutualism
  - dNeutralistic interactions
- 3Interactions between populations of different species and the ecological, evolutionary, and biogeographical aspects of interaction on the population level
CBiological communities
- 1Community structure
  - aVertical and horizontal patterns: the influence of variations in environmental conditions on the stratification and zonation of organisms
  - bTime relations: periodicity and population changes in the community
  - cInteractions in the community: heterotrophic nutrition, predation, symbiosis
  - dNiches and species diversity
  - eEcotones and the "edge effect"
- 2Community function: energy flow
- 3Community succession: growth toward a stable, mature condition
- 4Communities in space
  - aLandscape patterns: the habitats of a landscape as forming a pattern of environmental gradients
  - bClimax interpretation: monoclimax theory, polyclimax theory, and climax pattern hypothesis
  - cCommunity gradients: coenclines
- 5Community classification and its bases
  - aThe association as the unit of classification
  - bThe biome or formation as the unit of classification
  - cOther bases for classification: e.g., ecological succession, habitat, community metabolism