Ecological Succession: Primary and Secondary Processes

The session begins with an opener activity designed to model physiological succession.
Activity Materials: - Students are provided with cards containing stages of succession described in words. - These description cards are numbered (e.g., one, three, and beyond) to indicate the chronological order of events. - Students are tasked with matching corresponding pictures to these numbered descriptions.
Instructions: - Students are encouraged to use their notes if necessary. - The activity is performed collaboratively with peers at the table. - The goal is to order the pictures chronologically based on the descriptions provided.

Definition: Secondary succession occurs when an ecosystem builds off an area that was previously established but has been destroyed somehow.
Distinction from Primary Succession: While primary succession starts entirely from scratch, secondary succession involves rebuilding an ecosystem.
The Catalyst for Succession: A common example of a destroying force that leads to secondary succession is a "big fire."
Timescale and Speed: - Secondary succession takes place over a shorter timeframe compared to primary succession. - It typically occurs within a hundred years, whereas primary succession requires "hundreds and hundreds and hundreds of years."
The Mechanism of Rebuilding: - Ease of Recovery: It is generally easier to rebuild than to build from scratch. - Soil Readiness: The primary reason for the speed of secondary succession is that the soil is already "good to go." - Ecological Benefits of Fire: In some ecosystems, fire is beneficial; for example, certain trees only release their seeds following a fire event. - Resource Availability: Because the soil is already enriched, new organisms can move in immediately without waiting for the environment to be chemically modified.

Definition: Primary succession is the process of building an ecosystem entirely from scratch, starting with an environment that lacks usable soil.
Starting Point: The process begins with "barren rocks."
Pioneer Species - Lichen: - Composition: Lichen is described as a symbiosis, specifically a combination of "a couple different funguses and plants." - Function: The role of lichen is to break down the bare rock and convert it into usable soil.
Stages of Growth: - Once lichen creates usable soil, "really fast-growing resilient guys" (pioneer species) begin to grow. - Over time, these are replaced by "more long-lived plants."
Timescale: The process of breaking down rock into usable soil is slow, taking hundreds of years.

A critical distinction is made between "dirt" and "soil" regarding their capacity to support life: - Soil: Defined as "enriched" and specifically "nitrogen-rich." It contains the necessary nutrients for plants to grow. - Dirt: Described as having "nothing good for plants." It lacks the nutrients required for vegetation to establish itself.
Succession Application: In primary succession, the initial substrate is "dirt" (or rock) and must be converted into "soil." In secondary succession, the ecosystem retains its "good soil," allowing for rapid recolonization.

The instructor has transition away from "Cahoot" for these images and has posted them separately so students have access to clearer, non-confined pictures.
Case Study: Visual Comparison: - Students are asked to look at color pictures to see what the ecosystem "used to look like." - Image Modification: One image features a "Gemini AI guy" at the bottom. The instructor explains that the original picture was of such poor quality ("horrible") that they used AI to improve it for clarity.

Student/Teacher Interaction on Secondary Succession: - Instructor: "Secondary. Somebody not Davony. You agree with secondary. What's the explanation of why this is considered secondary?" - Student (unnamed): "Secondary is when they build off, like, a destroyed area already, and then primary is, like, when it's completely starting from the [scratch]." - Instructor: "K. So is when there was an already established place that gets destroyed somehow, then it rebuilds. Yeah. And then why it's at primary is when you're starting entirely from scratch."
Student/Teacher Interaction on Soil Mechanisms: - Instructor: "How would rebuilding take less time? … Nick?" - Nick: "The first and second stages are kind of combined and they take shorter." - Instructor: "What's the mechanism behind that? Why? It's gonna be easier to rebuild than to build from scratch. Fire is sometimes good." - Nick: "The soil has already taken for us." - Instructor: "The soil is, like, good to go. Like, we have good soil. We just killed everybody using it."