1.9.4Inquiry Process
Loss of Biodiversity — IB Biology HL Revision Notes & Topical Questions
5 min read 6 parts Lesson 35 of 160
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.
Section 1 of 6Measuring Biodiversity
Species richness
- Species richness The number of different species in an area, which ignores how many individuals each has.
Evenness
- Evenness How equally individuals are spread among species;
- a community dominated by one species is less diverse.
Simpson reciprocal index
- Simpson reciprocal index D = Σ(n/N)², where n is the number of one species and N the total;
- the index is 1/D and higher means more diverse.
Genetic diversity
- Genetic diversity The variety of alleles within a species, which allows adaptation to change and resists disease.
Ecosystem diversity
- Ecosystem diversity The variety of habitats and communities in a region.
Section 2 of 6Conservation Status
Conservation Status
IUCN Red List
- IUCN Red List Assesses species by population size, rate of decline and range, using standard categories.
Categories
- Categories Least concern, near threatened, vulnerable, endangered, critically endangered, extinct in the wild and extinct.
Use of the list
- Use of the list Helps governments and charities decide which species need most urgent protection.
Limits
- Limits Many species, especially invertebrates and microbes, have never been assessed.
| Category | Meaning |
|---|---|
| Vulnerable | High risk of extinction in the wild |
| Endangered | Very high risk |
| Critically endangered | Extremely high risk |
Section 3 of 6Why Biodiversity Matters
1
Diverse ecosystems are more stable and recover better after disturbance such as drought or disease.
2
Species provide food, medicines, timber and genetic resources for crops and livestock.
3
Pollination and pest control by wild species support farming.
4
Loss of genetic diversity, as in small populations, reduces ability to adapt to change.
5
Many cultures also value species for their beauty and ethical reasons.
Section 4 of 6Interpreting Index Values
Maximum value
- Maximum value The reciprocal index can never exceed the number of species, reached when all species are equally common.
Low values
- Low values A value near 1 shows one species dominates the community, as in a monoculture crop field.
Comparing sites
- Comparing sites A higher index at one site shows greater diversity, but samples must be of similar size and method.
Monitoring change
- Monitoring change Repeating surveys over years shows whether diversity is falling after disturbance or rising after restoration.
Section 5 of 6Worked Example
Question
- A sample of a woodland has 10 individuals of species A, 5 of species B and 5 of species C.
- Calculate Simpson reciprocal index and state what it shows.
- Total number N = 10 + 5 + 5 = 20.
- Calculate D = Σ(n/N)² = (10/20)² + (5/20)² + (5/20)² = 0.25 + 0.0625 + 0.0625 = 0.375.
- Simpson reciprocal index = 1 ÷ D = 1 ÷ 0.375 = 2.67.
Answer
- The index is 2.67 (to 3 s.f.).
- A higher value means greater diversity;
- the maximum possible here is 3, so the community is fairly even.
Section 6 of 6Exam Checklist & Tips
1.9.4 – Key Points for the Exam
- Biodiversity The variety of life at genetic, species and ecosystem levels.
- Species richness Number of species in a community.
- Simpson index A measure of diversity combining richness and evenness.
- IUCN Red List A global list of the conservation status of species.
Common Mistakes
- Using species richness alone and ignoring evenness.
- Putting the total N in the wrong place in Simpson calculation.
- Believing that genetic diversity is not part of biodiversity.
- Confusing endangered with extinct.
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