Ecological Succession

Ecological succession refers to the gradual and natural process of change in plant and animal communities within a specific habitat over time, ultimately leading to the establishment of a stable community.

Characteristics of Ecological Succession

  1. Occurs in newly formed habitats.
  2. Leads to an increase in the number of organisms.
  3. Follows an orderly and progressive pattern.
  4. Involves competition among organisms.
  5. Promotes diversity among organisms.

Pioneer Species & Climax Community

Pioneer Species

Pioneer species are the first organisms to colonize a new habitat, initiating the formation of new communities. These species typically have rapid reproductive strategies, allowing them to quickly establish in an uninhabited area. Many pioneer species reproduce asexually, which aids in their rapid colonization.

Pioneer Community

The pioneer community is the initial stage of any process of biological succession. This stage typically represents a harsh environment that supports limited plant and animal life. For example, a barren field has minimal layers to support diverse flora and fauna, with only ground and underground levels available for life.

Climax Community

The climax community is the stable, mature community that represents the final stage of ecological succession. At this stage, no further significant succession occurs. A climax community is formed after a sequence of species changes over time, and the specific species that constitute it vary depending on the biome.

Climax communities are more stable than pioneer communities and support a wider variety of plant and animal species. For example, a fully developed forest provides diverse habitats compared to an open field. Trees in the forest offer nesting sites for birds, homes for animals like squirrels and chipmunks, and shelter from environmental elements. Forests also provide habitats for larger animal species, making them more complex ecosystems than pioneer communities.

Types of Succession

  1. Primary Succession: This type occurs in areas devoid of biotic communities, such as bare rocks or barren land. It involves the gradual formation of soil and vegetation. For instance, in aquatic habitats, lakes and ponds may fill with sediments and vegetation, transforming into swamps and eventually forests. Primary succession takes a long time to reach a stable climax community. Natural events like landslides, droughts, sand dunes, earthquakes, and hurricanes can initiate primary succession.
  2. Secondary Succession: This type occurs in areas where a community previously existed but was disturbed, leaving behind soil and some organisms. Examples include areas affected by fires, floods, or droughts. Secondary succession progresses faster than primary succession due to the presence of existing soil and plant remnants that can restart the process.

Process of Ecological Succession in Terrestrial Habitats

  1. Pioneer organisms, such as algae and mosses, colonize the bare land.
  2. As these pioneers live and die, they contribute nutrients to the soil.
  3. The enriched soil creates favorable conditions for other plants like ferns and herbs, as well as lower animals like insects and worms.
  4. As these organisms live and die, they further enhance soil quality.
  5. Grasses, perennial herbs, and animals like lizards, snakes, toads, and rats begin to thrive.
  6. Eventually, the soil supports taller plants such as shrubs and trees, attracting higher animals.
  7. Birds, mammals, and other advanced organisms inhabit the habitat.
  8. A climax community is established, achieving equilibrium with the environment.

Characteristics of a Stable Community

  1. Undergoes gradual changes with age but remains relatively stable.
  2. Is in dynamic equilibrium with the regional climate and is self-sustaining.
  3. Supports the largest and most developed vegetation possible for the habitat.
  4. Contains numerous micro-habitats that accommodate various organisms.

Overcrowding

Overcrowding occurs when a population in a given habitat exceeds the resources available, such as space and food, leading to competition and resource scarcity.

Factors Leading to Overcrowding

Effects of Overcrowding

  1. Space shortage.
  2. Food scarcity.
  3. Anti-social behavior.
  4. Increased competition.
  5. Spread of diseases.
  6. Death of organisms.
  7. Predatory behavior among organisms.

Adaptations to Avoid Overcrowding

Food Shortage

Causes of Food Shortage

Effects of Food Shortage

  1. Increased competition for food, leading to aggression, predation, and the survival of the fittest.
  2. Poor nutrition, resulting in stunted growth, delayed maturity, and reduced reproduction rates. Mortality rates may increase, while birth rates decrease.
  3. Emigration, where individuals leave the habitat in search of food, reducing population density in the original area.