Syllabus concepts to know

• 2.5.1 Zonation refers to changes in community along an environmental gradient.
• 2.5.2 Transects can be used to measure biotic and abiotic factors along an environmental gradient in order to determine the variables that affect the distribution of species.
• 2.5.3 Succession is the replacement of one community by another in an area over time due to changes in biotic and abiotic variables.
• 2.5.4 Each seral community (sere) in a succession causes changes in environmental conditions that allow the next community to replace it through competition until a stable climax community is reached.
• 2.5.5 Primary successions happen on newly formed substratum where there is no soil or pre- existing community, such as rock newly formed by volcanism, moraines revealed by retreating glaciers, wind-blown sand or waterborne silt.
• 2.5.6 Secondary successions happen on bare soil where there has been a pre-existing community, such as a field where agriculture has ceased or a forest after an intense firestorm.
• 2.5.7 Energy flow, productivity, species diversity, soil depth and nutrient cycling change over time during succession.
• 2.5.8 An ecosystem’s capacity to tolerate disturbances and maintain equilibrium depends on its diversity and resilience.
• 2.5.9 The type of community that develops in a succession is influenced by climatic factors, the properties of the local bedrock and soil, geomorphology, together with fire and weather-related events that can occur.
• 2.5.10 Patterns of net productivity (NP) and gross productivity (GP) change over time in a community undergoing succession.
• 2.5.11 r- and K-strategist species have reproductive strategies that are better adapted to pioneer and climax communities, respectively.
• 2.5.12 The concept of a climax community has been challenged, and there is uncertainty over what ecosystems would develop naturally were there no human influences.
• 2.5.13 Human activity can divert and change the progression of succession leading to a plagioclimax.