A4.2Theme A — Unity and diversity
Conservation of biodiversity — IB Biology SL Revision Notes & Topical Questions
10 min read 12 parts Lesson 11 of 11 1 quiz
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.
Lesson summary
A4.2 Conservation of biodiversity — IB BIOLOGY SL notes: Describe the levels of biodiversity, the causes and evidence of its loss, and the in situ and ex situ conservation methods.Biodiversity = the variety of life in a specified areaMore biodiverse ecosystems are more stable and…
- Ecosystem diversity
- Species diversity
- Genetic diversity
- Number of species
- Change over time
- Classification accuracy
Part 1 of 10Levels of biodiversity
Biodiversity
Biodiversity the variety of life in a specified area
- More biodiverse ecosystems are more stable and resistant to change.
Ecosystem diversity
- Ecosystem diversity the range of habitats in an area
- A coral reef has many microhabitats, so its diversity is high.
- A large sandy desert has similar conditions throughout, so its diversity is low.
- A coast with reef, mangrove and seagrass has high ecosystem diversity.
Species diversity
- Species diversity it needs high richness and high evenness
- Species richness = the number of species in an ecosystem.
- Species evenness = how evenly the individuals are spread between the species.
- 1000 species with only a few individuals of 500 of them has high richness but low evenness.
- 10 species with thousands of individuals of each has high evenness but low richness.
Genetic diversity
- Genetic diversity the number of different alleles of genes in a species or population
- It depends on the proportion of genes with more than one allele and the number of alleles per gene.
- It helps a population adapt to and survive environmental change.
- Low genetic diversity reduces resistance to disease.
Part 2 of 10Counting species and stability
Counting species and stability
Number of species
- Number of species about 8.7 million are predicted and about 1.2 million have been recorded
- Many are unnamed, especially insects, fungi and microbes.
Change over time
- Change over time extinction has removed many past species, but speciation has outpaced extinction
- Global biodiversity is still higher than ever before.
Classification accuracy
- Classification accuracy it affects the estimates
- Lumpers stress similarities and merge groups, so the count is too low.
- Splitters stress differences and divide groups, so the count is too high.
Stability
- Stability diverse ecosystems resist change
- A forest dominated by one or two tree species could collapse from a single pathogen, as in the pine forests of Florida.
Part 3 of 10Extinction and case studies
Mass extinctions
- Mass extinctions there have been five, and the current losses could be a sixth
- The end-Cretaceous event ended the non-avian dinosaurs about 66 million years ago.
- Natural causes include asteroids, volcanism and climate shifts.
Anthropogenic extinction
Anthropogenic extinction extinction caused by human activities
- The current rate is far above the background rate and linked to human population and consumption.
North Island giant moa
- North Island giant moa a large flightless herbivorous bird of New Zealand
- Humans arrived between 1200 and 1300 and hunted it to extinction by about 1300.
Caribbean monk seal
- Caribbean monk seal docile and lay on rocks, so it was easy to hunt for oil and meat
- It was declared extinct in 2008.
Third case study
- Third case study choose a local species lost to humans
- Examples are the baiji, passenger pigeon, paradise parrot, golden toad and St Helena darter.
Island species
- Island species especially prone to extinction
Part 4 of 10Ecosystem loss
Ecosystem loss
Mixed dipterocarp forest in Southeast Asia
- Mixed dipterocarp forest in Southeast Asia a tropical rainforest that has lost more than 50% of its area in parts
- Clear-cutting removes all the trees for timber and to clear land for agriculture such as palm oil.
Second case study
- Second case study choose a local ecosystem lost to humans
- Examples are the Great Barrier Reef, the Northern Great Plains and mangrove forests.
Tropical rainforests
- Tropical rainforests hold over half of land species on under a tenth of the land
Part 5 of 10Evidence for biodiversity loss
Reliable evidence
- Reliable evidence surveys in a wide range of habitats, repeated over time
- Both species richness and evenness must be assessed.
- Experts must analyse the data.
Citizen scientists
Citizen scientists members of the public who help to collect data
- They increase the quantity of data but may reduce its quality.
- Good design and analysis offset this.
IPBES
- IPBES an intergovernmental body that gathers information, recommends policy and published a major report in 2019
IUCN
- IUCN a network of organisations and experts that keeps the Red List of threatened species
- Over 150 000 species have been assessed and over 42 000 are threatened.
Red List categories
- LC, NT, VU, EN, CR, EW and E for extinct, plus DD for data deficient and NE for not evaluated
- LC is least concern, NT near threatened, VU vulnerable, EN endangered, CR critically endangered, EW extinct in the wild.
Verifiable evidence
- Verifiable evidence it comes from peer-reviewed published sources so that methods can be checked
Part 6 of 10Causes of biodiversity loss
Causes of biodiversity loss
Human population
- Human population more than 8 billion people, still growing because births exceed deaths
Overexploitation
- Overexploitation overfishing and hunting for ivory, oil or fur faster than populations can recover
Urbanisation
- Urbanisation direct loss of habitat and fragmentation by roads, which pushes agriculture elsewhere
Deforestation
- Deforestation land cleared for agriculture, timber, mining and quarries
- Monocultures have very low biodiversity and cause loss of soil organisms.
- Habitat fragments become too small for many species.
Pollution
- Pollution microplastics reach remote places and pesticides can build up in food chains
Pests
- Pests monocultures let pests such as the cotton bollworm build up
Invasive species
- Invasive species brought by humans with no natural predators, so they outcompete natives
- Examples are grey squirrels and signal crayfish in the UK, cane toads in Australia and rats in the Galapagos.
Disease
- Disease chytrid fungus has driven about 90 amphibian species to extinction
- Climate change widens the range of some pathogens.
Climate change
- Climate change warming and acidification mean species must move or adapt
1
Excess fertiliser washes from farmland into a lake.
2
Nitrate and phosphate boost algal growth.
3
Algae block light and the plants below die.
4
Decomposers break down the dead matter and use oxygen.
5
Dissolved oxygen falls sharply.
6
Fish and invertebrates die and diversity falls.
Part 7 of 10In situ conservation
Protected areas
Protected areas defined spaces such as national parks and nature reserves managed for conservation
- National parks are government controlled, as with Kruger in South Africa.
- Nature reserves are smaller and can be on private or public land.
- Access is controlled, building and farming are regulated and hunting is limited or banned.
Rewilding
Rewilding restoring ecosystems until they sustain themselves
- Active rewilding uses human action, such as removing roads and reintroducing locally extinct species.
- Passive rewilding leaves an area alone so natural succession restores it.
- Passive rewilding fails for grassland, which needs grazing, as with the longhorn cattle at Knepp.
Reclamation
- Reclamation restoring land damaged by human activity, such as abandoned quarries or deforested areas
Part 8 of 10Ex situ conservation
1Zoos
- Zoos captive breeding raises numbers
- Artificial insemination moves genes between zoos to avoid low genetic diversity.
- Individuals may be released into the wild.
- Zoos also support research on genetics, behaviour and habitat needs.
- A captive breeding programme starts by identifying a species whose wild population is critically low.
- The remaining individuals are bred using studbooks to limit inbreeding, the habitat is restored, and animals are released gradually with monitoring.
2Botanic gardens
- Botanic gardens grow rare plants from wild seeds, cuttings or tissue culture for reintroduction and research
3Seed banks
- Seed banks dry seeds are stored cool in a controlled environment
- Seeds of one species are collected from different sites to maintain genetic diversity.
- Stored seeds are grown into plants to give fresh seeds.
- The Svalbard Global Seed Vault in Norway stores seeds in the Arctic Circle.
4Tissue banks (frozen zoos)
- Tissue banks (frozen zoos) store genetic material at very low temperatures
- Germplasm such as sperm, eggs and embryos can be used in captive breeding or IVF.
- Somatic tissue holds the full genome for DNA research and possible cloning.
Part 9 of 10Choosing which species to save
Limited funds
- Limited funds priorities must be set
EDGE programme
Evolutionarily Distinct and Globally Endangered, run with the Zoological Society of London
- Evolutionarily distinct species have few close relatives and are unusual in appearance, behaviour and DNA.
- They must be globally threatened according to the IUCN Red List, not just locally.
- Examples are the Chinese giant salamander, the purple frog and the largetooth sawfish.
Other factors
- Other factors ecological role, cultural value, politics, cost and conflict
- A species may matter because it supports an ecosystem holding more threatened species.
Decision
- EDGE passes on information and stakeholders debate and decide
Part 10 of 10More from the specification
1Anthropogenic biodiversity crisis
- Global acceleration of extinction rates driven by habitat destruction, overexploitation, pollution, and climate breakdown across the world.
2In situ vs ex situ conservation
- In situ conservation preserves organisms in their native ecosystems (national parks),
- whereas ex situ maintains captive species in zoos, botanical gardens, and seed banks.
3Keystone species preservation
- Protecting crucial ecological engineer species whose removal precipitates trophic cascades and widespread ecosystem collapse.
4International biodiversity treaties
- Coordinated global frameworks monitoring threatened species and regulating commercial wildlife trade.
- (e.g., CITES and the IUCN Red List)
Key terms
| Term | Meaning |
|---|---|
| Biodiversity | The variety of life in a specified area at ecosystem, species and genetic levels. |
| Species richness | The number of different species in an area. |
| Species evenness | How evenly individuals are spread between the species in an area. |
| Anthropogenic extinction | Extinction caused by human activities. |
| In situ conservation | Protecting species in their natural habitat, for example by reserves and rewilding. |
| Ex situ conservation | Protecting species outside their habitat, for example in zoos, seed banks and tissue banks. |
| Rewilding | Restoring an ecosystem to the point at which it sustains itself. |
| EDGE species | A species that is both evolutionarily distinct and globally endangered. |
Avoid these mistakes
1
Treating species richness as the whole of species diversity — evenness must be high as well
2
Saying all extinctions are natural — the current rate is far above the background rate and is linked to humans
3
Saying citizen science data are always unreliable — design and analysis can offset the loss of quality
4
Thinking passive rewilding works for every habitat — grassland needs grazing to stop trees taking over
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