A-Level Biology OCR A - Module 4 – Chapter 11 - Biodiversity
Disclaimer: These notes are for the OCR spec (but can be used for any spec). My notes do not cover
everything but it’s a pretty decent summary. Use at your own risk, there may be errors, but there shouldn’t
be. Also, some words are abbreviated.
Youtubers I recommend: BioRach, Free Science Lessons, Clare Biology, Miss Estruch.
What is biodiversity? → Variety of organisms, species and habitats in an area.
Why is biodiversity important? → Leads to interdependence of species (depend on one another)
Types of biodiversity → Species, habitat, genetic (variety of genes/alleles in organism)
What is species richness? → Number of diff species in a community.
What is species evenness? → A measure of the relative abundances of each species within a
community
What is a polymorphic loci? → Gene w more than 1 allele.
o How do u calculate the number of polymorphic loci? → Polymorphic loci / Total N of loci
Sampling
What is opportunistic sampling? → Choosing who you want to sample
What is stratified sampling? → Dividing a population into smaller grps known as strata, based on
characteristics that they share
What is systematic sampling? → A random sampling technique whereby data is collected in an
ordered or regular way through a belt or line transect.
How is reliability affected in sampling? → Bias (improve by doing random sampling), & chance
(improve by ↑ sample size to reduce effect of anomalies)
Maintaining biodiversity
How is biodiversity affected by humans? → Deforestation, agriculture (herbicides, monoculture),
climate change
Why shld we maintain biodiversity? → Aesthetic/economic reasons, medicine, greater genetic
diversity of crops, preserve keystone species
What is conservation? → Preservation or management of organisms or habitats
How to maintain biodiversity? → Conservation (+ agreements), sustainable development (in fishing
etc)
Examples of in situ conservation? → Wildlife reserves/marine conservation zones
Examples of ex situ conservation? → Zoos, botanic gardens, seed banks, captive breeding
programmes
What conservation agreement regulates international trade of wild species? → IUCN (International
Union for the Conservation of Nature) which has the CITES treaty (Convention on International
Trade in Endangered Species)
What does the Rio convention do? → Ensures sustainable development, Stabilises greenhouse gas
levels, ↓ Desertification
Which UK conservation agreement improves aesthetics + habitat biodiversity (raises awareness to
ppl so they want to protect it) → The countryside stewardship scheme.
