Population Ecology

Population Ecology Overview

  • Population Ecology is the study of how populations of a particular species interact with their environment.
  • It aims to understand factors affecting population growth and decline, population size and density, and the demographics of the population.
  • It involves studying relationships among individuals of the same species as well as interactions between different species.

Key Concepts in Population Ecology

  • The population is a group of individuals of a single species that occupy the same general area.
  • Populations are characterised by their size (number of individuals), density (number of individuals per unit area or volume), distribution or dispersion pattern (spatial arrangement of individuals), age structure, and sex ratio.
  • Population dynamics is the study of how these characteristics change in response to environmental conditions.
  • Birth rates (natality), death rates (mortality), immigration (influx of individuals), and emigration (outflow of individuals) are processes that affect population size.

Growth Models in Population Ecology

  • Exponential growth occurs when the individuals in a population reproduce at a constant rate. It is represented by a J-shaped curve.
  • Logistic growth occurs when a population’s growth slows or stops following a period of exponential growth, typically as resources become less available. It is represented by an S-shaped curve.
  • The carrying capacity is the maximum population size that a particular environment can support.

Survivorship Curves

  • Survivorship curves can help to illustrate the life history of a species, showing the proportion of individuals surviving to different ages.
  • There are three types of curves - Type I (low mortality at birth, most individuals live to old age), Type II (constant mortality rate throughout lifespan), and Type III (high mortality at birth with few individuals reaching adulthood).

Factors Affecting Population Growth

  • Density-dependent factors including resources availability, predation, disease, and competition tend to limit population growth and lead to logistic growth.
  • Density-independent factors like weather, climate, and human activities, can affect population size irrespective of its density.

Human Population Growth

  • The human population has been growing exponentially due to advancements in agriculture, sanitation, and medicine, but is expected to reach a logistic phase due to resource limitations.

Population Regulation and Conservation

  • Understanding how populations are regulated is critical for conservation biology and wildlife management.
  • Actions like protecting habitats, controlling invasive species, and implementing sustainable hunting and fishing practices are important in maintaining healthy population levels.