IB DP Biology Conservation of biodiversity Study Notes
IB DP Biology Conservation of biodiversity Study Notes
IB DP Biology Conservation of biodiversity Study Notes at IITian Academy focus on specific topic and type of questions asked in actual exam. Study Notes focus on IB Biology syllabus with guiding questions of
- What factors are causing the sixth mass extinction of species?
- How can conservationists minimize the loss of biodiversity?
Standard level and higher level: 3 hours
- IB DP Biology 2025 SL- IB Style Practice Questions with Answer-Topic Wise-Paper 1
- IB DP Biology 2025 HL- IB Style Practice Questions with Answer-Topic Wise-Paper 1
- IB DP Biology 2025 SL- IB Style Practice Questions with Answer-Topic Wise-Paper 2
- IB DP Biology 2025 HL- IB Style Practice Questions with Answer-Topic Wise-Paper 2
A4.2.1 – Biodiversity: Variety of Life in All Its Forms, Levels & Combinations
🌍 What Is Biodiversity?
Biodiversity refers to the variety of life on Earth from microscopic bacteria to towering redwood trees, and from coral reefs to deserts. It includes all living organisms, their genetic variation, and the ecosystems they form.
Biodiversity is the variety of life at all levels – genetic, species, and ecosystem and the ways these elements interact and evolve.
🧬 The Three Levels of Biodiversity
1️⃣ Genetic Diversity
Variation in genes within a species – includes differences between individuals or populations.
- Enables adaptation to changing environments
- Increases disease resistance
- Supports long-term survival
Example: Wheat varieties differ in genes for drought tolerance and seed traits.
2️⃣ Species Diversity
The number and variety of species in a particular habitat or region.
- Species richness – number of species
- Species evenness – distribution of individuals among species
Example: Coral reefs hosting 1,000+ species of fish.
3️⃣ Ecosystem Diversity
Refers to the variety of ecosystems and their environmental conditions and organisms.
- Provides essential services like pollination and water purification
- Supports different life forms adapted to various conditions
Example: Rainforests, mangroves, alpine meadows, and coral reefs are all unique ecosystems.
📊 Summary Table: Three Levels of Biodiversity
| Level | What It Means | Example |
|---|---|---|
| Genetic Diversity | Variation of genes within a species | Different dog breeds or rice strains |
| Species Diversity | Number and types of species in a habitat | Insects, birds, mammals in rainforests |
| Ecosystem Diversity | Variety of ecosystems and interactions | Deserts, savannas, coral reefs, tundra |
🌿 Why Is Biodiversity Important?
- Stability: Diverse ecosystems are more resilient to disturbances.
- Medicine: Many pharmaceuticals come from natural compounds.
- Food Security: Genetic diversity protects against crop failures.
- Ecosystem Services: Biodiversity ensures:
- Clean air and water
- Pollination
- Soil fertility
- Climate regulation
🚨 Threats to Biodiversity
- Habitat destruction
- Climate change
- Pollution (air, land, water)
- Genetic erosion (loss of crop/livestock diversity)
- Overexploitation (e.g., overfishing, hunting)
📌 Interesting Facts:
Scientists estimate 8 million+ species exist, but only ~2 million have been identified.
Rainforests and coral reefs are the most biodiverse ecosystems on Earth.
Losing biodiversity weakens ecosystem stability – including those we rely on.
🧠 Key Recap
- Biodiversity includes:
- Genetic diversity (within species)
- Species diversity (between species)
- Ecosystem diversity (between environments)
- It supports: Adaptation, ecosystem health, and resources for humans
- It is threatened – conservation is essential for life on Earth
A4.2.2 – Comparing Present-Day and Past Biodiversity Levels
🌱 How Many Species Exist Today?
Over geologic time, biodiversity has generally increased – with more complex and varied life forms emerging after each extinction event.
Over 2 million species have been discovered, named, and described. Scientists estimate that over 8 million species may exist in total – meaning millions remain undiscovered. New species are frequently found in rainforests, oceans, and soils.
🧬 Biodiversity Through Time: A Dynamic History
Earth’s biodiversity has changed over millions of years, shaped by evolution and extinction. After mass extinctions, new species often evolved to fill ecological gaps.
💥 Mass Extinction Events
| Extinction Event | When | Impact |
|---|---|---|
| Ordovician–Silurian | ~444 million years ago | 85% of marine species lost |
| Devonian | ~375 million years ago | 75% species lost |
| Permian–Triassic | ~252 million years ago | 96% marine species lost (“The Great Dying”) |
| Triassic–Jurassic | ~200 million years ago | 80% species lost |
| Cretaceous–Paleogene (K–Pg) | ~66 million years ago | 76% species lost (e.g., non-avian dinosaurs) |
📊 How Does Today Compare with the Past?
Today’s biodiversity is likely the highest in Earth’s history – but it’s rapidly declining due to human actions. Scientists warn that we may be entering a sixth mass extinction.
🌍 High biodiversity today is being offset by habitat loss, overexploitation, and climate change.
🚨 Extinction is occurring 1,000× faster than natural background rates.
🧪 NOS (Nature of Science): The Role of Classification
Scientists use classification to group organisms based on shared features – but interpretation plays a role too:
| Approach | Philosophy | Effect |
|---|---|---|
| Splitters | Prefer to divide life into more specific species | Higher species counts |
| Lumpers | Group organisms more broadly | Lower species counts |
🔍 Real-World Insight: Human Influence on Biodiversity
- Climate change, pollution, and habitat destruction are key drivers of extinction.
- Species like the Javan rhino and many amphibians are critically endangered.
- Conservation biology aims to protect and restore biodiversity.
🧠 Key Recap
| Aspect | Current Biodiversity | Past Biodiversity |
|---|---|---|
| Species Count | ~2 million known; possibly >8 million | Much lower after mass extinction events |
| Discovery Status | Millions undiscovered | Based on fossil record (incomplete) |
| Mass Extinctions | Human-driven 6th extinction risk | 5 known over 500+ million years |
| Classification View | Splitters vs. Lumpers affect count | Similar taxonomic biases exist |
Today’s biodiversity is at an all-time high – but faces serious threat.
Past mass extinctions show biodiversity can recover – but it takes millions of years.
Classification is interpretative, and understanding biodiversity is vital for protecting life on Earth.
A4.2.3 – Causes of Anthropogenic Species Extinction
🛑 The Sixth Mass Extinction: A Human-Made Crisis
Unlike previous mass extinctions driven by natural causes, the sixth mass extinction is happening now – and it’s caused by humans. Anthropogenic extinction refers to the loss of species directly or indirectly due to human activity.
Extinction of species caused by human actions like overhunting, pollution, deforestation, and climate change.
🔍 Main Human-Driven Causes of Species Extinction
1. Overexploitation
Excessive hunting, fishing, and harvesting for food, skins, medicine, or luxury items (e.g., ivory, shark fins). Species are removed faster than they can reproduce.
2. Habitat Destruction
Deforestation, urbanization, farming, and mining destroy ecosystems. Habitat fragmentation isolates populations and increases vulnerability.
3. Invasive Species
Non-native species introduced by humans can outcompete, prey on, or infect native species. Particularly harmful in isolated ecosystems like islands.
4. Pollution
Includes chemical waste, plastic, and agricultural runoff. Pollutants damage reproductive systems, poison species, and degrade habitats.
5. Climate Change
Changes temperature, rainfall, and sea levels. Forces species to migrate or adapt quickly. Coral bleaching and altered ecosystems are key effects.
🧪 Case Studies of Human-Caused Extinction
| Species | Type & Location | Cause of Extinction |
|---|---|---|
| North Island Giant Moa | Terrestrial bird, New Zealand | Hunted to extinction by Maori, large and flightless |
| Caribbean Monk Seal | Marine mammal, Caribbean Sea | Overhunted for oil and meat, habitat loss |
| Pink-headed Duck | Freshwater bird, India & Bangladesh | Habitat loss from wetland drainage, overhunting |
🌍 Key Patterns Across Case Studies
- Extinction is usually caused by multiple human factors acting together.
- Species with narrow ranges or slow reproduction are at greater risk.
- Extinctions often happen rapidly once human impacts begin.
🧠 Nature of Science (NOS): Complexity of Classification
Declaring a species extinct isn’t always straightforward. Some are rediscovered after decades, showing the limits of documentation and the challenges of taxonomy.
🧪 Takeaway: Extinctions today are happening 1,000× faster than natural background rates – and humans are the primary cause. Protecting biodiversity requires urgent global conservation efforts.
🧠 Summary Box – Causes of Anthropogenic Extinction
| Cause | Effect on Biodiversity |
|---|---|
| Overexploitation | Rapid population decline due to hunting or harvesting |
| Habitat Destruction | Loss and fragmentation of natural habitats |
| Invasive Species | Displace or kill native species; spread disease |
| Pollution | Harms reproduction, contaminates food chains |
| Climate Change | Alters habitats faster than species can adapt |
A4.2.4 – Causes of Ecosystem Loss
🌍 What Is Ecosystem Loss?
Ecosystem loss is the degradation, fragmentation, or complete destruction of natural habitats due to human activity. It disrupts ecological networks and eliminates ecosystem services essential to life.
Clean air & water, fertile soil, climate regulation, food supply, flood control, and pollination.
🚧 Major Anthropogenic Causes of Ecosystem Loss
All of the following are human-driven:
1. Land-Use Change
Conversion of forests, wetlands, and grasslands into farmland, housing, and roads – the most widespread driver of habitat loss.
2. Urbanization
Cities and industrial areas fragment habitats, cutting off species movement and gene flow.
3. Overexploitation
Excessive logging, fishing, and hunting deplete resources, leading to deforestation, extinction, and erosion.
4. Pollution
Air, water, and soil pollution from plastic, sewage, pesticides, and chemicals disrupt sensitive ecosystems.
5. Climate Change
Alters rainfall, temperature, and sea levels. Threatens climate-sensitive systems like coral reefs and alpine zones.
6. Mining & Dam Construction
Strip mining and dams destroy habitats and pollute rivers, altering water flow and aquatic ecosystems.
Case Study 1: Mixed Dipterocarp Forest – Southeast Asia
| Location | Ecosystem | Key Threats | Impact |
|---|---|---|---|
| Borneo, Sumatra | Mixed Dipterocarp Rainforest | Logging, palm oil plantations, slash-and-burn farming | Loss of orangutans & tigers, increased CO₂, erosion, flooding |
📌 Note: Dipterocarps form the forest canopy and support diverse food webs – their loss collapses entire rainforest ecosystems.
Case Study 2: Wetland Loss – Pallikaranai, India
| Location | Ecosystem | Key Threats | Impact |
|---|---|---|---|
| Pallikaranai, Tamil Nadu | Freshwater Marsh | Urban encroachment, solid waste dumping, sewage discharge | Bird loss, degraded water, increased flooding risk |
📌 Note: Wetlands filter water, regulate floods, and support species like flamingos and herons – but are disappearing rapidly.
📊 Summary Table: Human-Caused Ecosystem Loss
| Cause | Impact on Ecosystems |
|---|---|
| Land-use change | Destroys habitats, reduces ecosystem functions |
| Urbanization | Fragments ecosystems, isolates species |
| Overexploitation | Depletes natural resources and species |
| Pollution | Damages air, soil, water; harms life |
| Climate change | Alters habitats too fast for adaptation |
| Mining & dams | Destroy habitats, disrupt rivers and water flow |
Ecosystem loss is mainly human-driven.
It affects biodiversity, food security, and climate.
Conservation, policy change, and sustainable development are critical to protect remaining ecosystems.
A4.2.5 – Evidence for a Biodiversity Crisis
🌍 What Is a Biodiversity Crisis?
The biodiversity crisis is the ongoing, rapid decline in global species, ecosystems, and genetic diversity — mostly caused by human activities. To confirm this scientifically, we rely on measurable and peer-reviewed evidence.
🔬 Sources of Scientific Evidence
1. IPBES Reports
The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) provides global peer-reviewed reports.
- 2019 Global Assessment → ~1 million species threatened with extinction.
- 75% of terrestrial & 66% of marine environments significantly altered by humans.
- Loss is faster than at any time in human history.
2. Long-Term Biodiversity Surveys
Repeated surveys track species richness, evenness, and population trends across decades.
- Living Planet Index (WWF & ZSL) – Measures global wildlife population trends.
- IUCN Red List Index – Tracks extinction risk over time.
3. Habitat-Level Monitoring
Satellites and field data confirm degradation and loss of key habitats:
- Amazon deforestation
- Coral reef bleaching
- Wetland shrinkage
4. Genetic and Ecosystem Diversity Metrics
Declining genetic variation is documented in wild species, crops, and livestock.
Ecosystem function (e.g., nutrient cycling, biomass) is deteriorating in stressed habitats.
📸 Role of Citizen Science
| Advantages | Concerns |
|---|---|
| Broad data coverage, even in remote areas | Data may lack consistency or standardization |
| Detects early signs of population shifts | Needs proper training and expert review |
| Engages the public with conservation | Peer-review may be lacking |
🧪 Examples: eBird (birds), iNaturalist (plants, animals), Butterfly Monitoring Schemes – all contribute valuable data on trends, migrations, and seasonal shifts.
Nature of Science (NOS): What Counts as Scientific Evidence?
🔍 Reliable scientific evidence must be:
Peer-reviewed or from reputable scientific bodies
Repeatable (consistent methodology)
Transparent and clear in how data is gathered and interpreted
Citizen science is helpful but requires verification. When paired with expert review and standardized methods, it strengthens global biodiversity tracking.
🧠 Summary Table – How We Know There’s a Crisis
| Evidence Type | What It Shows |
|---|---|
| IPBES Reports | Global biodiversity decline and human impact trends |
| Biodiversity Indices | Decline in species populations worldwide |
| Habitat Monitoring | Deforestation, bleaching, wetland loss observed via satellites |
| Citizen Science | Expands observations, early detection of changes |
| Peer Review | Ensures scientific credibility and global acceptance |
Biodiversity loss is real, measurable, and accelerating. The crisis is supported by global surveys, indices, satellite evidence, and verified citizen data. Science provides the tools – now global action must follow.
A4.2.6 – Causes of the Current Biodiversity Crisis
🌍 What Is Causing the Biodiversity Crisis?
The current biodiversity crisis stems from several human-driven pressures occurring simultaneously. At its root lies unchecked human population growth, intensifying demands on ecosystems and species worldwide.
More people → more pressure on nature → faster biodiversity loss.
1. Human Population Growth (The Overarching Driver)
The global population has surpassed 8 billion, increasing demands for housing, food, water, and energy.
- Leads to urban expansion, deforestation, and resource depletion.
- Magnifies habitat loss, overexploitation, and pollution.
2. Over-Exploitation (Hunting, Fishing, Trade)
Excessive hunting and fishing reduce wildlife populations faster than they can recover.
- Wildlife trade threatens species like pangolins, parrots, and big cats.
- Example: African elephants are endangered due to ivory poaching.
3. Urbanization
Cities and roads replace ecosystems, fragmenting habitats and introducing light, noise, and traffic hazards for animals.
- Urban sprawl has eliminated natural corridors and green belts.
4. Deforestation & Agricultural Expansion
Forests are cleared for agriculture and livestock, especially for crops like palm oil, soy, and maize.
- Example: Rainforests in Borneo are cleared for palm oil plantations, threatening orangutans.
5. Pollution
Pollution affects ecosystems via air, water, and soil contamination.
- Plastic pollution harms birds, fish, and marine life.
- Example: Microplastics have been detected in fish, birds, and even humans.
6. Spread of Pests, Diseases, and Invasive Alien Species
Global transport introduces invasive species and diseases into ecosystems unprepared for them.
- Examples: Rats and cats on islands wiping out birds; chytrid fungus killing amphibians.
- India: Lantana camara and water hyacinth disrupt native vegetation.
📊 Summary Table – Key Causes of the Biodiversity Crisis
| Cause | How It Contributes |
|---|---|
| Human population growth | Drives demand for land, food, and energy; amplifies all other threats |
| Over-exploitation | Unsustainable hunting and fishing reduce populations drastically |
| Urbanization | Replaces and fragments natural habitats, isolating species |
| Deforestation & agriculture | Destroys forests and grasslands, affecting forest-dependent species |
| Pollution | Toxic chemicals, plastic, and sewage harm ecosystems and species |
| Invasive species & disease | Outcompete or kill native species; disrupt ecosystem balance |
🧠 Final Takeaway:
The biodiversity crisis is driven by human behavior, with population growth amplifying all other threats.
Solutions include:
- Sustainable development
- Stronger environmental laws
- Conservation of key habitats
- Global cooperation on pollution and invasive species control
🌿 Protecting biodiversity = Protecting Earth’s future.
A4.2.7 – The Need for Multiple Approaches to Biodiversity Conservation
🌿 Why We Need Diverse Conservation Strategies
Biodiversity conservation cannot rely on a single method. Different species, habitats, and threats require different often complementary approaches.
What works for a rainforest may not work for a coral reef or desert plant.
🛑 Why One-Size-Fits-All Doesn’t Work
Species differ in habitat, population dynamics, and reproductive biology. Biodiversity threats include deforestation, pollution, climate change, overexploitation, and invasive species. Some species thrive only in the wild, others may require human-managed survival.
🏞️ In Situ Conservation – Protecting Nature in Nature
Definition: Conservation of species within their natural ecosystems.
- Protected areas (e.g. national parks, wildlife sanctuaries)
- Legal species protection and habitat monitoring
Example: Kaziranga National Park (India) conserves the endangered one-horned rhinoceros.
🌲 Management of Nature Reserves
Creating and maintaining protected ecosystems through active management.
- Controlling invasive species
- Restoring habitats
- Establishing buffer zones and migration corridors
Example: Yellowstone National Park (USA) manages predator-prey balance using wolves and elk.
🐻 Rewilding & Ecosystem Reclamation
- Rewilding: Reintroducing lost species to restore ecological function
- Reclamation: Repairing damaged or degraded ecosystems
- Goal: Let ecosystems self-regulate and support biodiversity
Examples: Wolves reintroduced in Yellowstone; mangrove restoration in coastal India.
🏛️ Ex Situ Conservation – Conserving Outside Natural Habitat
Definition: Protection of species outside their native ecosystems.
- Zoos, aquariums, and botanic gardens
- Captive breeding and gene banking
Example: California condor was bred in captivity and reintroduced into the wild.
🌱 Seed Banks and Germplasm Storage
Germplasm: Genetic material (e.g., seeds, embryos, tissues) stored for future use.
- Preserves crop and plant diversity for food security
- Protects against climate and disease-related extinction
Example: Svalbard Global Seed Vault (Norway) stores seeds from every region of the world.
📊 Summary Table – Conservation Approaches
| Approach | Description | Key Benefit |
|---|---|---|
| In situ conservation | Protecting species in their natural habitats | Preserves entire ecosystems and ecological interactions |
| Nature reserve management | Active monitoring and intervention within protected zones | Boosts ecosystem health and resilience |
| Rewilding & reclamation | Restoring ecosystems or reintroducing lost species | Rebuilds ecological functions and species networks |
| Ex situ conservation | Breeding or storing species outside the wild | Backup when wild populations are critically low |
| Seed/germplasm banks | Storing genetic resources (seeds, embryos, tissues) | Secures future biodiversity and agricultural stability |
🧠 Final Takeaway:
Biodiversity is far too complex for a single solution.
Effective conservation requires:
- In situ protection of species and habitats
- Ex situ backups and breeding programs
- Restoration of degraded ecosystems
- Long-term planning, research, and public participation
🌍 “Conservation isn’t just about species – it’s about sustaining Earth’s life support systems.”
A4.2.8 – Prioritizing EDGE Species for Conservation
🧬 What Are EDGE Species?
EDGE stands for Evolutionarily Distinct and Globally Endangered. These are species with few or no close relatives and are at serious risk of extinction.
Losing one of these species means losing an entire branch of the evolutionary tree.
Evolutionarily unique
Critically endangered
Globally irreplaceable
🌳 Why Prioritize EDGE Species?
Conservation resources are limited. EDGE helps focus efforts where the evolutionary loss would be greatest:
- Preserves deep evolutionary history
- Protects species with no close relatives
- Maximizes long-term biodiversity retention
Losing a pangolin is worse than losing one frog from a species-rich group with hundreds of relatives.
📊 How Are EDGE Scores Calculated?
| Component | What It Measures |
|---|---|
| Evolutionary Distinctiveness (ED) | How isolated a species is on the tree of life |
| Global Endangerment (GE) | How threatened the species is (based on IUCN Red List) |
| ➡️ EDGE Score = ED × GE | |
Examples of EDGE Species
| Species | Why It’s EDGE |
|---|---|
| Axolotl (Ambystoma mexicanum) | Unique amphibian; extremely endangered; endemic to Mexico |
| Pangolins (family Manidae) | Only scaled mammals; ancient lineage; heavily poached |
| Aye-aye (Daubentonia madagascariensis) | Weird, rare primate with no close relatives; native to Madagascar |
| Yangtze giant softshell turtle | One of the rarest turtles; possibly only 2-3 left in existence |
🧠 Nature of Science (NOS): Ethical and Practical Dilemmas
Choosing what species to save isn’t just about science – it’s also about values, ethics, economics, and culture.
| Dimension | Dilemma |
|---|---|
| Ethical | Should we save rarer species over more common but declining ones? |
| Environmental | Will species-focused conservation help or harm whole ecosystems? |
| Economic | Should funds go to charismatic species that attract donations? |
| Political | Can conservation succeed in unstable or poor regions? |
| Cultural | Should we interfere when species are part of local traditions? |
🧠 Summary Box – EDGE Conservation Approach
Evolutionary Distinctiveness: Protects species with no close relatives
Global Endangerment: Focuses on critically endangered species
EDGE Score: Combines ED × GE for setting priorities
Strategic Focus: Saves maximum evolutionary history with limited resources
Ethical Layer: Includes human values and socio-political considerations
🌍 Final Takeaway:
The EDGE approach is science-backed and strategy-driven.
It prevents not just extinction, but the loss of entire evolutionary lineages.
“Protecting EDGE species means saving the rarest stories of life on Earth.”