Difference Between Primary & Secondary Succession

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What is Ecological Succession?

The process of evolution of the structure of the biological species is known as ecological succession. It is the process of change in the species structure of a community in an ecosystem over a while. The time scale is usually long, which may range from decades, or natural destruction- for example, after a wildfire, or even millions of years after a mass extinction. The cause of ecosystem change or what fuels ecological succession is the impact that the established species make upon their environments.


Characteristics of Ecological Succession

Thus, Succession is the order of colonization of species in an ecosystem from a barren or destroyed area of land and the one from already inhabited lands.

Ecological succession is the steady and gradual change in a species of a given area of land. This change occurs concerning the changing environment of that particular ecosystem. It is a predictable and inevitable process of nature as all the biotic components have to keep up with the changes in the environment.

It takes place until an equilibrium is reached in the ecosystem and the community that achieves it is called the climax community.

The sequence of changing communities over a period is called sere and each community that arrives in the process is called a seral community.

It is a part of nature right from the Earth’s existence. Therefore, it is the process that takes place simultaneously along with evolution.

Primary succession is a slower process than secondary succession. Because, life has to start from a zero, whereas secondary starts at a place that had already supported life before.


Types of Ecological Succession

An ecological Succession is initiated either by the formation of new, unoccupied habitat, such as from a lava flow or a severe landslide, or by some form of disturbance of a community, such as from a wildfire, severe windthrow, or logging, which may wipe out the entire species. Thus, succession is of two types-

• Primary Succession - Succession that begins in new habitats or lifeless areas that are uninfluenced by pre-existing communities is called primary succession.

• Secondary Succession - Succession that follows the disruption of a pre-existing community that existed in the same ecosystem is called secondary succession.


Primary Succession

Primary succession is the type of ecological succession that starts in lifeless areas. It is the one in which plants and animals first colonize a barren, lifeless habitat such as the regions devoid of soil or the areas where the soil is unable to sustain life. The pioneer species or the first species build an initial biological community that is simpler in form. This community gradually becomes more complex with the arrival of new species.

When the planet was first formed, it was just a mere sphere of gases with the absence of soil. It evolved to contain only rocks in place of soil. These rocks were eroded by physical conditions and broken down by microorganisms to form soil. The soil then became the primary foundation of plant life. Various animal species adapted to survive on plants. Thus, it progressed gradually from primary succession to the climax community. 


Secondary Succession

The secondary is the second type of ecological succession that occurs when the primary ecosystem gets destroyed. Thus, it is the type of succession in which plants and animals recolonize a habitat after a major disturbance like a landslide, lava flow, wildfire, etc. It occurs when a climax community gets destroyed. Secondary succession takes place in an ecosystem where the disturbance did not eliminate all life forms and nutrients from the environment. Small plants emerge, followed by larger plants at the beginning of the succession. They develop into tall trees that block the sunlight and change the structure of the organisms below the canopy. By the end of all this, the climax community arrives.

Mostly insects and weedy plants are the first organisms to recolonize in secondary succession. Gradually more complex and stable species of plants and animals arrive. Stability in the ecological structure of a biological community is established when the area remains undisturbed for a long period.

Difference Between Primary & Secondary Succession

Properties

Primary Succession

Secondary Succession

Meaning

It is a type of succession that starts from barren or uninhabited land.

It is the type of succession which occurs in a habitat where life existed previously.

Occurs

It occurs in lifeless or barren areas.

It occurs in recently denuded or previously inhabited areas.

Time to complete

Takes around 1000 years, which may be more.

It takes place in 50 to 200 years.

Physical Conditions

Conditions are least suitable for the survival of life. Soil is devoid of nutrients or there is no soil at all.

As life once existed. There is the presence of soil and may also even some nutrients in the soil.

Humus

Humus is absent.

Humus is present due to the presence of previous inhabitants.

Seral community

There are several intermediary seral communities.

Few intermediary seral communities are present, compared to the primary succession.

Environment

It begins with an unfavorable environment.

The environment is more or less favorable right from the beginning.

Reproduction

No previous community so reproductive structure starts from the first inhibiting species.

Reproductive structure varies from primary succession due to the presence of previous communities in that habitat.

Examples

Bare rock, ponds, desert, lava-filled lands, etc.

The areas that are affected by natural calamities, covered under deforestation, or devastated by human interactions, etc.

FAQ (Frequently Asked Questions)

1. What is Ecological Succession?

The process of evolution of the structure of the biological species is known as ecological succession. It is the process of change in the species structure of a community in an ecosystem over a period of time. It is of two types- Primary Ecological Succession and Secondary Ecological Succession.

2. What is a Pioneer Community?

It is a community of organisms that occupy the area undergoing primary succession. They are simpler live forms that can survive in the bare minimum and withstand extreme conditions. They are mostly microorganisms. These organisms go through various seral stages to evolve into the climax community consisting of more complex and stable organisms.