Diversity of organisms — A/L Biology

What must I remember about Diversity of organisms?

• The three-domain classification system (Woese): Domain Bacteria, Domain Archaea, and Domain Eukarya based on rRNA sequence analysis and cellular ultrastructure.
• Domain Bacteria vs Archaea: Bacteria have peptidoglycan cell walls and ester-linked unbranched lipids; Archaea lack peptidoglycan, have ether-linked branched lipids, and inhabit extreme environments (extremophiles).
• Eukaryotic kingdoms: Kingdom Protista (paraphyletic single/colonial eukaryotes), Kingdom Fungi (absorptive heterotrophs with chitin cell walls), Kingdom Plantae (autotrophic, cellulose walls, alternation of generations), Kingdom Animalia (ingestive heterotrophic multicellular organisms).
• Plant kingdom evolutionary ladder: Non-vascular bryophytes (mosses, dominant gametophyte) ⟶ Seedless vascular lycophytes/monilophytes (ferns) ⟶ Gymnosperms (naked seeds: Cycas, Pinus) ⟶ Angiosperms (flowering plants, enclosed seeds).
• Animal kingdom evolutionary milestones: Symmetry (radial vs bilateral), tissue organization (diploblastic vs triploblastic), body cavity (coelom: acoelomate, pseudocoelomate, coelomate), and embryology (protostome vs deuterostome).

Test yourself (1 minute)

1. Alternation of generations

   Sporophyte (diploid, 2n) produces haploid spores via MEIOSIS; Gametophyte (haploid, n) produces gametes via MITOSIS.

2. Gymnosperm vs Angiosperm seed reproduction

   Gymnosperms have naked ovules on cones and single fertilization; angiosperms have enclosed ovules in ovaries, flowers, and double fertilization.

Practise Diversity of organisms questions today

Must know

• Chordate diagnostic characteristics (present at some stage of life): Notochord, dorsal hollow nerve cord, pharyngeal gill slits, and post-anal tail.

Source: NIE G.C.E. (A/L) Biology Syllabus & Resource Book, Unit 3

What comes next?

Next in the syllabus

Where does Diversity of organisms fit in the syllabus?

Year 1 · Term 3