Succession

Ecological Succession

  • Definition: Ecological succession is a process that occurs following a disturbance in an ecosystem.

Purpose of Succession

  • Regeneration and Creation: Succession regenerates or creates a community after a disturbance.
  • Nature of Succession: It is characterized as a sequence of biotic changes where damaged communities are regenerated and new communities arise in previously uninhabited areas.

Types of Ecological Succession

  • There are two types of succession:
    • Primary Succession
    • Initiation: Begins with pioneer species, such as lichens and mosses.
    • Occurrence: Takes place in previously uninhabited areas.
    • Example: Primary succession can occur when bare rock is exposed by a receding glacier.
    • Secondary Succession
    • Initiation: Starts with remaining species from the previous ecosystem.
    • Occurrence: Happens after disturbances like fires or natural disasters.

Stages of Primary Succession

  • Pioneer Stages:
    • Initial colonization by species such as lichens on bare rock.
    • Followed by small annual plants and lichens.
  • Intermediate Stages:
    • Development of perennial herbs and grasses.
    • Inclusion of more complex life forms such as grasses, shrubs, and shade-tolerant trees.
  • Climax Community:
    • This represents the final stage of succession where the ecosystem is stable and fully developed, taking hundreds of years to reach.

Disturbances Leading to Succession

  • Types of Disturbances Leading to Succession:
    • Primary Succession
    • Examples: Exposure of bare rock from glacial retreat.
    • Secondary Succession
    • Examples: Occurs after disturbances such as:
      • Forest fires
      • Natural disasters (e.g., hurricanes, floods)
      • Deforestation (human-induced)
      • Volcanic eruptions

Dispersal Patterns in Ecology

  • Population Distribution Patterns: The manner in which organisms are distributed in their environment can be categorized into three patterns:
    • Clumped Distribution:
    • Organisms are clustered together in groups.
    • This may indicate a patchy distribution of resources in the environment, making clumped distribution the most common pattern of population dispersion.
    • Random Distribution:
    • Organisms are distributed unpredictably.
    • This is typical of species where individuals do not interact strongly with others.
    • Uniform Distribution:
    • Organisms are evenly spaced over the area they occupy.
    • This pattern is commonly found in species competing for scarce resources, such as water in desert environments.

Types of Speciation

  • Speciation refers to the evolutionary process by which new biological species arise. There are two primary types of speciation:
    • Allopatric Speciation:
    • This process occurs due to geographical isolation of populations.
    • Sympatric Speciation:
    • This occurs due to reproductive isolation, where new species evolve from a common ancestor while they are still in the same environment.