1.6.4Additional lessons
Loss of Biodiversity — IB Biology SL Revision Notes & Topical Questions
5 min read 4 parts Lesson 9 of 142
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Part 1 of 4Measuring and Evidencing Loss
Claims about biodiversity loss are only reliable when they rest on repeatable, verifiable data.
Biodiversity levels
- Biodiversity levels Biodiversity can fall in ecosystem diversity, species diversity (richness and evenness) or genetic diversity within a population.
Repeat surveys
- Repeat surveys Evidence needs the same area surveyed with the same methods over many years, so that changes in species numbers are comparable.
Expert analysis
- Expert analysis Survey data must be analysed by specialists and often combined from many sites before a global trend is claimed.
IPBES
- IPBES The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services reviews evidence and reports on global trends.
IUCN Red List
- IUCN Red List The International Union for Conservation of Nature classifies the extinction risk of species using standard criteria.
| Category | Code | Meaning |
|---|---|---|
| Least concern | LC | Widespread and abundant |
| Near threatened | NT | Close to qualifying as threatened |
| Vulnerable | VU | High risk of extinction in the wild |
| Endangered | EN | Very high risk of extinction |
| Critically endangered | CR | Extremely high risk of extinction |
| Extinct in the wild | EW | Survives only in captivity or cultivation |
| Extinct | EX | No individuals remain |
Part 2 of 4Causes of Biodiversity Loss
Causes of Biodiversity Loss
Population growth
- Population growth A growing human population needs more land, food and resources, which increases pressure on natural habitats.
Overexploitation
- Overexploitation Taking wild species for food, medicine or trade faster than they can reproduce causes populations to decline.
Habitat loss
- Habitat loss Deforestation and urbanisation remove habitat directly, while roads fragment what remains into isolated patches.
Pollution
- Pollution Pollutants such as pesticides and microplastics reach even remote environments and harm organisms or disrupt food chains.
Invasive species and disease
- Invasive species and disease Non-native species such as cane toads in Australia and rats on islands outcompete or prey on native species.
Part 3 of 4Biodiversity and Pests
1
In diverse ecosystems many predators and competitors keep any single herbivore or pest species at a low number.
2
Farmers clear land and grow one crop over a large area, which is a monoculture with little other wildlife.
3
Predators of pests lose their habitat and food, so their numbers fall.
4
Pests find an abundant food supply and few enemies, so their populations grow quickly.
5
Greater pesticide use follows, which can further reduce biodiversity and pollute nearby ecosystems.
Part 4 of 4Exam Checklist & Tips
1.6.4 – Key Points for the Exam
- Biodiversity The variety of life in an area, measured at ecosystem, species and genetic levels.
- IUCN Red List A global assessment that places species into categories according to their risk of extinction.
- Monoculture Large-scale cultivation of a single species.
- Overexploitation Harvesting a resource faster than it can be renewed.
- Fragmentation Splitting of a continuous habitat into smaller isolated areas.
Common Mistakes
- Using one survey as proof of a long-term decline; repeat surveys over time are needed.
- Mixing up Endangered and Extinct in the wild; endangered species still live in the wild.
- Listing causes without linking each to a mechanism, such as roads fragmenting habitat.
- Treating biodiversity as only the number of species and forgetting genetic and ecosystem diversity.
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