What is the primary difference between biotic and abiotic factors?

Biotic factors are the living components of an ecosystem (e.g., plants, animals, bacteria), while abiotic factors are the non-living physical and chemical elements (e.g., sunlight, temperature, soil moisture).

How does species richness differ from species evenness?

Richness is the total number of different species present in an area, whereas evenness describes how close in numbers the populations of each species are, indicating if one species dominates the landscape.

What is the distinction between genetic diversity and species diversity?

Genetic diversity refers to the variation of DNA and traits within a single species, while species diversity refers to the variety and abundance of different species within a specific habitat or ecosystem.

What is a common misconception regarding the 'climax community' in succession?

A common error is assuming a climax community is permanent and unchanging; in reality, it exists in a state of dynamic equilibrium and can be reset by natural disturbances like fires or storms.

Why is it incorrect to define sustainability solely as 'protecting the environment'?

Sustainability must also account for social equity and economic viability (the Triple Bottom Line); ignoring human needs often leads to the failure of environmental protection efforts.

What error is made when confusing 'habitat' with 'ecosystem'?

A habitat is simply the physical place where an organism lives, while an ecosystem includes both the habitat and the complex web of interactions between all living organisms and their environment.

Define 'Sustainable Development'.

Development that meets the needs of the present without compromising the ability of future generations to meet their own needs, balancing environmental, social, and economic factors.

What are 'Supporting Services' in an ecosystem?

These are fundamental processes such as nutrient cycling, soil formation, and primary production (photosynthesis) that are necessary for the production of all other ecosystem services.

A large geographical area of the earth's surface with similar climatic conditions that support specific communities of plants and animals adapted to that environment.

A conservation approach aimed at restoring natural ecosystem processes and reducing human influence, often by reintroducing key species to restore ecological balance.

Key Terms: Ecosystems & Sustainability | AQA A-Level Geography

Ecosystems Under Stress

Key Terms: Ecosystems & Sustainability

Summary

This topic explores the fundamental components of ecological systems and the principles of maintaining their health and viability over time. It focuses on the intricate balance between living organisms and their physical environment, the stages of natural development, and the frameworks required to ensure that human progress does not deplete the natural capital necessary for future generations.

1. Definition & Core Concepts

Ecosystem: A functional unit consisting of a community of living organisms (biotic factors) interacting with their non-living physical environment (abiotic factors), such as sunlight, soil, and water.
Sustainability: The capacity to maintain or improve the health of a system over the long term; in a human context, it refers to meeting current needs without compromising the ability of future generations to meet theirs.
Biome: A large-scale ecological region characterized by specific climatic conditions, soil types, and distinct assemblages of flora and fauna, such as tropical rainforests or tundras.

Venn diagram showing the interaction between Biotic (living) and Abiotic (non-living) components forming an ecosystem.

2. Biodiversity Dimensions

Genetic Diversity: The range of different inherited traits within a species, which is crucial for adaptation and survival in changing environments.
Species Diversity: A combination of species richness (the number of different species) and evenness (how close in numbers each species in an environment is).
Ecosystem Diversity: The variety of different habitats, communities, and ecological processes within a geographical area.

3. Ecological Succession

Ecosystem Succession: The directional and predictable process by which the structure of a biological community evolves over time, often starting from bare ground or a disturbed area.
Climatic Climax Community: The final, stable stage of succession where the vegetation is in equilibrium with the local climate and remains relatively unchanged unless a major disturbance occurs.
Rewilding: A conservation strategy focused on restoring natural processes and wilderness areas, often involving the reintroduction of apex predators or keystone species to trigger self-regulating ecosystems.

4. Sustainable Development Principles

5. Key Distinctions

6. Exam Strategy & Tips