🌱 Biodiversity and Ecosystem Resilience
Big Idea: Biodiversity is like having a big, talented team. The more variety, the better an ecosystem can handle problems and bounce back (resilience).
What is biodiversity?
Biodiversity means all the different living things in an area. It’s like having lots of different players on a sports team.
- Habitat diversity (e.g., a park with ponds, woods, and meadows)
- Species diversity (e.g., birds, insects, trees, and flowers all in one place)
- Genetic diversity
How does biodiversity help resilience?
Ecosystems with lots of different species are stronger and recover faster from problems, like storms or disease.
- More species = more connections (like a spider web with lots of threads)
- Complex food webs can handle losing one species (if one thread breaks, the web still holds)
- Ecosystems keep working even after change (like a team with lots of substitutes)
More biodiversity = more backup = more resilience!
Redundancy: Nature’s Backup Plan
In diverse ecosystems, several species can do the same job. If one is lost, others can fill in.
- If bees disappear, other insects (like butterflies or flies) can still pollinate flowers.
- If one kind of fish is gone, others might eat the same food.
- This backup system keeps the ecosystem running.
Redundancy = backup workers for every job in nature.
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What happens if biodiversity is lost?
With fewer species, ecosystems are weaker and can break down more easily.
- Fewer species = fewer connections (like a weak spider web)
- Simple food webs are easy to break
- Disturbances (like disease or pollution) have a bigger impact
- Ecosystems can reach a tipping point (e.g., a forest turning into grassland after too many trees are lost)
How are the levels of biodiversity connected?
All three levels of biodiversity work together, like parts of a machine.
- More habitats = more places for species to live (e.g., a rainforest has trees, rivers, and ground cover)
- More species = more genetic diversity (e.g., lots of types of birds means more variety within each type)
- Genetic diversity helps species adapt to change (e.g., some plants survive drought better than others)
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IB-style question — Resilience and species diversity
Outline how both species diversity and population size influence the resilience of a freshwater lake ecosystem. [4]
How to answer it, step by step
- Species diversity → resilience
• More species = functional redundancy: if one disappears, another fills its role.
• Complex food webs have alternative pathways, so one loss doesn't collapse the network. - Population size → resilience
• Larger populations = more genetic diversity, so some individuals survive new stresses.
• Small populations go locally extinct more easily, weakening the web further.
Final answer
Cover BOTH diversity AND population size, and always state the resilience consequence (recovery/stability) explicitly.
IB-style question — Three levels of biodiversity
The figures provided measure biodiversity only at the species level. Name one other recognised level of biological diversity. [1]
How to answer it, step by step
- Two accepted answers
• Genetic diversity — variation in alleles within a species.
• Habitat (ecosystem) diversity — variety of habitat types in an area. - What NOT to write
• Do not write 'species richness' or 'evenness' — these are parts of species diversity, not a separate level.
Final answer
One mark for 'genetic diversity' OR 'habitat diversity' — either phrasing that clearly means the same concept is accepted.