📌Definition Table

Term	Definition
Biodiversity	Variety of life at all levels: genetic, species, and ecosystem.
Genetic Diversity	Variation of alleles within a population’s gene pool.
Species Diversity	Variety of species in an ecosystem, measured by richness and evenness.
Species Richness	Number of different species present in a given area.
Species Evenness	Relative abundance of each species in an ecosystem.
Ecosystem Diversity	Variety of habitats, communities, and ecological processes in the biosphere.
Endemism	Species found only in a specific geographic location.

📌Introduction

Biodiversity encompasses the full range of life forms on Earth and the natural patterns they form. It exists at three main levels — genetic, species, and ecosystem — and is vital for ecological stability, resilience, and the provision of ecosystem services. High biodiversity generally means greater ecosystem resilience, while low biodiversity can make systems more vulnerable to disturbances.

❤️ CAS Link: Partner with a local park authority to create an illustrated biodiversity map of the area, showcasing species richness and endemism

📌 Levels of Biodiversity

• Genetic Diversity — High genetic variation allows species to adapt to environmental change and resist diseases.
• Species Diversity — Measured by:
  • Richness (number of species present).
  • Evenness (balance of population sizes among species).
• Ecosystem Diversity — Range of different habitats and communities within a region, e.g., tropical rainforest vs. desert.

🧠 Examiner Tip: When given data, use both richness and evenness to assess biodiversity — not just species counts.

📌 Examples of High vs. Low Biodiversity

• High biodiversity: Coral reefs (many species, balanced abundances, high genetic diversity).
• Low biodiversity: Monoculture crop fields (few species, low genetic variation).
• Biodiversity hotspots are regions with high species richness and high levels of endemism (e.g., Madagascar, Amazon rainforest).

🌍 Real-World Connection: Conservation International identifies 36 global biodiversity hotspots covering 2.3% of Earth’s land surface yet hosting over 50% of endemic plant species.

📌Biodiversity Over Time

• Biodiversity changes through speciation (formation of new species) and extinction.
• Natural extinctions are balanced by speciation over geological timescales.
• Mass extinction events dramatically reduce biodiversity but can be followed by adaptive radiation.
• Current biodiversity loss rates are 100–1000× the natural background rate due to human activities.

📝 Paper 2: Data Response Tip: If given biodiversity data before and after disturbance, calculate % change and explain with ecological reasoning (e.g., loss of evenness, habitat destruction).