Ecological succession is directional community change over time after new habitat forms or disturbance resets an existing ecosystem with remaining resources.
Ecological succession is the gradual change in species composition and community structure over time.
Early colonists modify light, soil, nutrients and microclimate, enabling or excluding later species. Disturbance and control loops determine the pathway.
Identify the starting condition, colonist effect and later community change.; separate state, pressure, control loop and time
After a field is abandoned, grasses alter soil and shade, allowing shrubs and eventually trees to establish. This gives a concrete prediction from the stated ecosystem.
Succession is not a fixed march to one climax everywhere; climate and disturbance alter pathways. Interpret the result within the stated model and evidence limits.
This objective is assessed through structured response, commonly using State / Distinguish / Suggest.
State / Distinguish / Suggest
Build the answer around this relationship: Succession describes changes in organism communities through time.
Representative question
Distinguish between primary succession and secondary succession, giving an example of each.
primary succession
secondary succession
on newly formed land
previously occupied land;
eg volcano
eg after forest fire;
no organic content
soil with organic content;
no organisms present at start
organism may be present at start;
slower/longer process
quicker process;
To award [3] an example must be provided.
A table format is not necessary.
HL D4.2 is the long-term change story. Succession begins after new habitat or disturbance, pioneer species modify conditions, primary succession builds soil and complexity, and some systems repeat cycles or are held before climax by disturbance.
HL succession questions focus on community pathways over time. The answer starts from the initial condition, shows how species modify abiotic conditions and interactions, and identifies whether the pathway is primary, cyclical, climax, or arrested by repeated disturbance.