Preview
IB DP Biology — A: Unity and Diversity | SL | A4.2 Conservation of Biodiversity
📋 What You Will Learn
- Identify the three levels of biodiversity — genetic, species, and ecosystem — and explain why each level matters for conservation
- Explain how Simpson's Diversity Index is calculated and interpreted as a quantitative measure of biodiversity
- Analyse data from biodiversity surveys to evaluate the health of ecosystems and the effectiveness of conservation interventions
- Describe in situ and ex situ conservation strategies, including their biological rationale, advantages, and limitations
- Evaluate the role of international agreements, protected areas, and captive breeding programmes in preserving biodiversity
- Apply understanding of biodiversity to unfamiliar ecological contexts, including habitat fragmentation, invasive species, and keystone species
🔍 Guiding Question How can biodiversity be measured, and what strategies can be used to preserve it?
🌍 Why This Matters In 1992, scientists discovered that a single hectare of Amazonian rainforest could contain over 400 tree species — more than all of northern Europe combined. That staggering density of life is not just beautiful; it is the biological insurance policy that keeps ecosystems functioning under pressure. When we lose species, we lose the ecological interactions that hold communities together — and once those threads unravel, the whole fabric can collapse.
What Is Biodiversity — and Why Measure It?
Here is the problem every conservation biologist faces: you cannot protect what you cannot measure. Saying an ecosystem is "rich" or "depleted" is not science — it is an impression. To make decisions about where to direct limited conservation resources, we need numbers. We need a way to compare a degraded farmland hedgerow with an ancient woodland, or a bleached coral reef with a healthy one. That is exactly what biodiversity indices give us.
But biodiversity itself is not a single thing. It operates at three distinct levels, each telling a different part of the story. Understanding all three is essential — both for the exam and for understanding why conservation is genuinely complex.
📖 Key Definition — Biodiversity Biodiversity is the variety of life on Earth at all its levels, from genes to ecosystems. It encompasses the evolutionary, ecological, and cultural processes that sustain life.
Level 1 — Genetic Diversity
Genetic diversity is the variety of alleles within a species or population. It is the raw material of evolution — without it, a population cannot adapt to changing conditions. A cheetah population with very low genetic diversity, for example, is dangerously vulnerable to a single novel pathogen because nearly every individual carries the same immune gene variants. High genetic diversity means that at least some individuals are likely to survive any new selective pressure.
Genetic diversity is measured using techniques such as gel electrophoresis to compare allele frequencies, or more recently through genome sequencing. For conservation, maintaining genetic diversity often means managing breeding programmes to avoid inbreeding, or facilitating gene flow between isolated populations through wildlife corridors.
📖 Key Definition — Genetic Diversity Genetic diversity is the total number of genetic characteristics — including alleles, genes, and chromosomes — in the genetic makeup of a species or population. It is the foundation of a population's capacity to adapt through natural selection.
Level 2 — Species Diversity
Species diversity is the most familiar level — it is what most people mean when they say an ecosystem is "biodiverse." But species diversity is not simply a count of how many species are present (species richness). It also includes species evenness: how evenly individuals are distributed among those species. An ecosystem with 10 species but 99% of individuals belonging to just one of them is far less diverse — in any