A4.2Theme A — Unity and diversity
Conservation of biodiversity — IB Biology HL Revision Notes & Topical Questions
10 min read 11 parts Lesson 13 of 14 1 quiz
Lesson summary
A4.2 Conservation of biodiversity — IB BIOLOGY HL notes: Explain the levels of biodiversity, the causes of its loss and the in situ and ex situ methods used to conserve it.Biodiversity = the variety of life in a specified area, and more biodiverse ecosystems are more stable and r…
- Ecosystem diversity
- Species diversity
- Genetic diversity
- Numbers of species
- Fossil record
- Nature of science
Part 1 of 9Levels of biodiversity
Biodiversity
Biodiversity the variety of life in a specified area, and more biodiverse ecosystems are more stable and resilient.
Ecosystem diversity
- Ecosystem diversity the range of habitats in an area.
- A coral reef with many microhabitats and niches has high diversity, and a large sandy desert has low diversity.
Species diversity
- Species diversity it needs both richness and evenness to be high.
- Species richness = the number of species in an ecosystem.
- Species evenness = the number of individuals of each species.
- 1000 species with few individuals of 500 of them gives high richness but low evenness,
- and 10 species with thousands of individuals each gives high evenness but low richness.
Stability
- Stability high species diversity makes an ecosystem more resilient,
- whereas Florida pine forests dominated by one or two species could collapse if a pathogen kills a dominant tree.
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.
- Populations differ because of different selection pressures, and individuals within a population also differ.
- Genetic diversity helps a population adapt to environmental change.
Part 2 of 9Changes in biodiversity over time
Numbers of species
- Numbers of species about 8.7 million species are estimated on Earth, and about 1.2 million have been recorded, so many remain to be found.
Fossil record
- Fossil record many past species are extinct, yet more species are alive today than in the past.
- When speciation is faster than extinction, global biodiversity rises, so levels remain higher than ever despite recent extinctions.
Nature of science
- Nature of science estimates depend on classification.
- Species wrongly grouped together make estimates too small.
- Species wrongly separated make estimates too large.
- Lumpers focus on similarities and group species, while splitters focus on differences and separate them.
Part 3 of 9Anthropogenic species extinction
Anthropogenic extinction
Anthropogenic extinction extinction caused by human activities.
Mass extinction
- Mass extinction there have been five past mass extinctions, and the present one could be the sixth, with human activity a large factor.
| Species | Details | Cause |
|---|---|---|
| North Island giant moa | Large flightless herbivorous bird of New Zealand, extinct by 1300 | Humans arrived between 1200 and 1300 and hunted it to extinction |
| Caribbean monk seal | Lived around the Gulf of Mexico and Caribbean, declared extinct in 2008 | Docile seals resting on rocks were easy to hunt for oil and meat |
- Third case study
- a locally relevant species extinct from human activity must be studied, for example baiji, passenger pigeon, paradise parrot, golden toad or St Helena darter.
Part 4 of 9Ecosystem loss
Ecosystem loss
Ecosystem
Ecosystem all living organisms in an area with their interactions and the non-living environment.
Mixed dipterocarp forest of Southeast Asia
- Dipterocarps are tropical trees forming the core of a complex rainforest.
- Some areas have lost over 50% of their forest.
- Clear-cutting removes all trees for timber and for agriculture such as palm oil plantations.
Second case study
- Second case study a human-caused ecosystem loss must be studied, for example the Great Barrier Reef, Northern Great Plains or mangrove forests.
Part 5 of 9Evidence for biodiversity loss
Trustworthy evidence needs many surveys in a wide range of habitats, repeat surveys over time, assessment of richness and evenness,
- and expert analysis.
Citizen scientists
Citizen scientists members of the public who help collect survey data.
- They increase the quantity of data, but they are often untrained, so quality may fall.
- Good design and analysis reduce the effect.
IPBES
- IPBES gathers information, recommends policy and communicates findings on biodiversity and ecosystem services,
- and published a comprehensive report in 2019.
IUCN
- IUCN a network of organisations and experts that proposes environmental policy and keeps the Red List.
- The Red List has assessed over 150 000 species and listed over 42 000 as threatened.
Nature of science
- Nature of science evidence should come from a published, peer-reviewed source whose methodology can be checked.
| Code | IUCN category |
|---|---|
| LC | Least concern |
| NT | Near threatened |
| VU | Vulnerable |
| EN | Endangered |
| CR | Critically endangered |
| EW | Extinct in the wild |
| E | Extinct |
- Data deficient (DD) and not evaluated (NE) are also used.
Part 6 of 9Causes of biodiversity loss
1Population growth
- Population growth more than 8 billion people live on Earth, and births exceed deaths so the population is projected to rise until 2100.
2Overexploitation
- Overexploitation overfishing and hunting for ivory, whale oil or fur.
3Urbanisation
- Urbanisation buildings destroy habitat, roads fragment it, and agriculture expands elsewhere.
4Deforestation and habitat loss
- Deforestation and habitat loss land is cleared for agriculture, timber, mining and quarries.
- Monocultures have very low diversity and cause loss of soil micro-organisms.
5Pollution
- Pollution microplastics occur in remote environments and fertilisers and organic waste wash into water.
6Pests
- Pests pests such as the cotton bollworm increase because lower diversity means fewer predators, and monocultures let pests gather.
7Invasive species
- Invasive species humans carry alien species to new habitats.
- Examples are grey squirrels and signal crayfish in the UK, cane toads in Australia and rats in the Galapagos.
8Disease
- Disease chytrid fungus is thought to have wiped out 90 amphibian species.
- Climate change extends disease ranges.
- Close contact with animals lets pathogens transfer to new hosts.
Part 7 of 9In situ conservation
Conservation conflicts
- Conservation conflicts human needs and natural needs conflict, so a mixture of approaches is needed.
Protected areas
Protected areas defined spaces such as national parks and nature reserves managed for conservation.
- National parks are government-controlled, and nature reserves are smaller and can be private or public.
- Human access is controlled, building and agriculture are regulated and hunting is limited or banned.
- Kruger National Park is the largest national park in South Africa.
Rewilding
Rewilding restoring ecosystems until they sustain themselves, which makes them biodiverse.
- Active rewilding uses intervention such as removing roads and reintroducing locally extinct species.
- Passive rewilding leaves the area alone so succession restores it.
- Passive rewilding fails for some habitats such as grassland,
- which needs grazing to stop trees dominating, as with longhorn cattle on the Knepp estate.
Reclamation
Reclamation restoring areas damaged by humans, such as abandoned quarries or deforested land, to their previous ecosystem.
Part 8 of 9Ex situ conservation
1
Zoos
- Captive breeding raises numbers, and artificial insemination moves genes between zoos to protect genetic diversity.
- Animals may be released to the wild.
- Zoos support research on genetics, behaviour and habitat needs.
2
Botanic gardens
- They use wild cuttings and seeds to establish captive populations of endangered plants.
- Tissue culture and cloning give many plants from small samples.
- Plants can be reintroduced, and research covers reproduction, growth and habitat needs.
3
Seed banks
- Seeds are dried and stored in cool, dry, temperature-controlled conditions to stay viable.
- Seeds are periodically grown out and fresh seeds are stored, and seeds from several sites keep genetic diversity.
- The Svalbard Global Seed Vault in Norway holds seeds from almost 1 million plant species in the Arctic Circle.
4
Tissue banks (frozen zoos) store tissue at very low temperatures, possibly indefinitely, from different individuals to keep diversity.
- Germplasm (sperm, eggs, embryos) supports captive breeding and, in theory, IVF with a surrogate species.
- Somatic tissue holds the full genome, for DNA research and possible cloning of extinct species.
Part 9 of 9Prioritising species for conservation
EDGE programme (Evolutionarily Distinct and Globally Endangered), working with the Zoological Society of London, sets priorities.
Evolutionarily distinct
- Evolutionarily distinct a species has few close relatives, is unusual in appearance, behaviour and DNA,
- and represents a unique part of the evolutionary tree.
Globally endangered
- Globally endangered the Red List must show a global threat, not only a local one.
Both conditions are needed, and examples are the largetooth sawfish, Chinese giant salamander and purple frog.
Nature of science
- Nature of science priorities involve ethical, environmental, political, social, cultural and economic issues.
- A less threatened species may support an ecosystem containing more threatened species.
- A species may be culturally important to a nation.
- Conservation may be difficult for political reasons, such as a habitat lying in a war zone.
- EDGE passes on information and does not itself make conservation decisions.
Key terms
| Term | Meaning |
|---|---|
| Biodiversity | the variety of life in an area at ecosystem, species and genetic levels. |
| Species richness | the number of species in an ecosystem. |
| Species evenness | how evenly individuals are spread among the species. |
| Anthropogenic | caused by human activity. |
| In situ conservation | protecting species in their natural habitat. |
| Ex situ conservation | protecting species outside their natural habitat, as in zoos and seed banks. |
| Rewilding | restoring an ecosystem until it can sustain itself. |
| EDGE species | a species that is both evolutionarily distinct and globally endangered. |
| Citizen scientist | a member of the public who helps collect survey data. |
Avoid these mistakes
1
High species richness alone means high diversity — evenness must also be high.
2
Speciation has stopped so biodiversity must be falling steadily — past speciation means global diversity is still higher than ever, though extinction is rising.
3
Ex situ conservation protects the habitat — it conserves organisms away from their natural habitat.
4
Passive rewilding always works — habitats like grassland need grazing to stay open.
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