This lesson covers succession in biology. You’ll learn the difference between primary and secondary succession and look at some specific examples of succession in different ecosystems.
What Is Succession?
When it comes to inheritance law, a successor is a person who comes after you in a family lineage. Your father was your grandfather’s successor, and you are your father’s. As your father’s successor, you will likely inherit his money when he dies.
But you’ll change that money a little bit before you eventually pass it on to your own kids. You might invest it or use it to buy property. Those things will be passed onto your children, and in the same way, they’ll use that inheritance, change it, and pass it on to their children.Although biology has to do with living species, not money or inheritance, the idea of succession in biology is the same. Succession in biology is the order in which species appear in an ecosystem over time. So, like your father passes his money on to you, the first species in an environment passes on the changes it has made to the second species. The second species changes the environment a little more, maybe creating more ground cover or changing the soil, and then passes that on to the third species to inhabit the area, and so on.
Order of Succession
The species that colonize a new area of land do so in a specific order. Although the species in ecosystems may be different, the general order of succession is the same. Pioneer species are the first species to arrive on the scene. They’re usually small plant-like species, like lichen or moss. After the pioneer species are established, larger plants can inhabit the area, like grasses, then shrubs. Finally, trees start to grow and the forest ecosystem reaches a stable place again.
Succession happens when an environment has been cleared of life, either through a minor disturbance, like a fire, or through something major, like a volcanic eruption. There are two kinds of succession based on the type of disturbance, primary and secondary succession.
Primary succession occurs when a community, or group of species, evolves from a barren land with no life at all. The soil is completely fresh and devoid of life. An example of primary succession occurs after a volcanic eruption. Hot lava spews from the Earth, coating the land around it. This area near the volcano starts with no life at all.
Eventually, seeds will land there and pioneer species will begin to colonize the area. The pioneer species will begin to break down the volcanic rock and establish soil that other plants can grow in.
Secondary succession occurs when there is disturbance that destroys the life in an ecosystem, but remnants, like soil, nutrients, and some seeds, still remain. An example is a forest fire.
Although the fire burns through the trees and disrupts the animals’ habitat, the basic necessities for life remain. Since there is already nutrient rich soil, the pioneer species do not need to prepare the area for other plants, and succession can occur more quickly. Other incidents that may result in secondary succession include high winds from hurricanes or tornadoes or excessive flooding.When either type of succession has reached an equilibrium, the ecosystem is said to be in a climax stage. The living things in the ecosystem will remain at equilibrium without any drastic change in the makeup of species until another disaster occurs to induce succession.
Examples of Succession
Primary succession occurs when a barren area of land is first colonized.
An interesting example is the colonization of mining or rock quarries. Humans mine ores, minerals and coal for industrial purposes, leaving barren land sources in the quarries. These areas have never been colonized by life previously. However, ecologists are now interested in both the spontaneous succession and reclamation in these areas after humans introduce soil and species to them.
These methods have been successful in primary succession of mosses, flowering plants and insects like butterflies and bees.A natural example of secondary succession occurs in the grasslands of the Midwestern United States. Grasslands actually periodically burn to the ground to maintain their ecosystem. Some plants’ seeds are only triggered to grow by the intense temperatures of a fire. The fires prevent larger shrubs and trees from growing over the grasses necessary for this ecosystem. After the fire burns the existing grasslands, new grass seeds are triggered to grow. As the grass grows, larger plants, insects and animals inhabit the area again until the next fire.
Since there was an existing ecosystem before the fire, this is an example of secondary succession.
In summary, succession in biology is the order of colonization of species in an ecosystem from a barren or destroyed area of land. Pioneer species, like moss and lichen, are the first to colonize an area.
They change the environment so it is suitable for larger plants, like shrubs and grass. Trees colonize the area in the final stages of succession.There are two types of succession. In primary succession, the land is barren and has never been colonized before, like volcanic rock or a rock quarry.
In secondary succession, an ecosystem previously existed, but was disrupted, usually by a natural disaster like a fire or hurricane. When succession has reached a peak, the ecosystem is in a climax stage, where all species are in equilibrium.