Life is astonishingly diverse yet clearly related. This SL lesson covers A3.1 Diversity of organisms, A3.2 Classification & cladistics, A4.1 Evolution & speciation and A4.2 Conservation of biodiversity.
You will use the species concept, three-domain classification, cladograms, mechanisms of speciation and Simpson's diversity index.
Work through each screen, answer the questions as you go (some are wordy, some are calculations) and collect ⭐ stars. Press Start when you are ready.
A species is usually defined as a group whose members can interbreed to produce fertile offspring. Every species has a two-word binomial name (genus + species), e.g. Panthera leo.
Organisms vary in chromosome number and in traits, but all share DNA, a genetic code and cellular organisation — unity within diversity.
The biological species concept can be hard to apply to asexual organisms, extinct species or ring species — a good evaluation point.
Organisms are classified into a hierarchy: domain → kingdom → phylum → class → order → family → genus → species.
The three domains are Archaea, Bacteria and Eukarya, based largely on ribosomal RNA sequences.
Cladistics groups organisms into clades using shared derived features — especially DNA and protein sequences. A cladogram shows these relationships and can be recalibrated with a molecular clock.
Evolution is supported by homologous structures (e.g. the pentadactyl limb), the fossil record, selective breeding, biogeography and molecular sequence similarities.
Homologous = same ancestry, possibly different function (unity). Analogous = same function, different ancestry (convergent evolution).
Speciation is the splitting of one species into two, usually through reproductive isolation.
Over time, isolated gene pools diverge until they can no longer interbreed.
Sort each example into the correct conservation category (or threat).
Biodiversity is falling due to habitat loss and fragmentation, overexploitation, invasive species, pollution and climate change.
Diversity indices such as Simpson's quantify both species richness and evenness.
Match each term to its correct description.
A3.1 Diversity: species and binomial naming; unity of the genetic code
A3.2 Classification: three domains; clades built from sequence data (cladistics)
A4.1 Evolution: homology as evidence; allopatric vs sympatric speciation
A4.2 Conservation: in-situ vs ex-situ; Simpson's index quantifies biodiversity
Press Finish to see your score.
You have worked through Theme A: Unity & Diversity — Organisms & Ecosystems for IB Diploma Biology. 🎉
Your stars: 0 / 0
Next: test yourself in the Evaluate stage Confidence Quiz, then lock it in with Verify.