Biodiversity and threats — A/L Biology

What must I remember about Biodiversity and threats?

• Biodiversity (biological diversity) is the variety of life on Earth across three hierarchical levels: Genetic Diversity (allelic variation within populations), Species Diversity (species richness and relative abundance in an ecological community), and Ecosystem Diversity (variety of habitats, communities, and ecological processes across biomes).
• Direct economic value of biodiversity: Food security (wild crop relatives for drought/pest resistance), pharmaceuticals (>50% prescription drugs derived from natural plant/microbial extracts), industrial raw materials (timber, fibers, resins), and ecotourism.
• Indirect ecological ecosystem services: Carbon sequestration and climate regulation, watershed catchment protection and water purification, soil erosion prevention and nutrient cycling, and crop pollination by insects/birds.
• Major anthropogenic threats summarized by the HIPPO dilemma: Habitat destruction and fragmentation (deforestation, agricultural conversion), Invasive alien species, Pollution (pesticides, plastics, eutrophication, acid rain), Population growth of humans, and Overexploitation (overfishing, poaching, illegal logging).
• IUCN Red List Categories evaluate extinction risk: Extinct (EX), Extinct in the Wild (EW), Critically Endangered (CR), Endangered (EN), Vulnerable (VU), Near Threatened (NT), and Least Concern (LC); CR, EN, and VU constitute the 'Threatened' categories.

Test yourself (1 minute)

1. Habitat Fragmentation & Edge Effects

   Fragmenting contiguous forests into small isolated patches increases edge-to-interior ratios, altering microclimates (increased wind, dessication, light) and exposing interior species to invasive predators and nest parasites.

2. Invasive Alien Species (IAS) in Sri Lanka

   Plants like Eichhornia crassipes (water hyacinth), Salvinia molesta, Lantana camara, and animals like Chitala ornata (clown featherback) outcompete native species and destabilize aquatic and terrestrial food webs.

3. Endemism vulnerability

   Endemic species with narrow geographic ranges, specialized habitats, or low reproductive rates are inherently the most prone to catastrophic extinction following human disturbances.

Practise Biodiversity and threats questions today

Source: NIE G.C.E. (A/L) Biology Syllabus & Resource Book, Unit 6

What should I study first?

What comes next?

Next in the syllabus

Where does Biodiversity and threats fit in the syllabus?

Year 2 · Term 2