General Biology II · Module 6 · Protists

Protists Lab

Scan a drop of pond water and key out what swims past; break the malaria life cycle with nets, insecticides and drugs and watch the infection graph respond; practise membrane counting, growth math and life cycle stages; sort protists by supergroup, role and movement; and use it all on real cases. Nothing here is graded.

Part 1: Pond Microscope Bench

Microscope readouts
MeasureValue
Field guide: a key to pond protists
  1. Covered in many short, beating cilia? Go to 2. No cilia? Go to 4.
  2. Bell-shaped, fixed to debris by a stalk that coils and springs back: Vorticella. Free-swimming: go to 3.
  3. Trumpet-shaped, very large (1 mm or more), often blue-green: Stentor. Slipper-shaped, about 0.2 mm, with an oral groove and two star-shaped contractile vacuoles: Paramecium.
  4. Changes shape and crawls with lobe-like pseudopodia: Amoeba. Keeps its shape: go to 5.
  5. Golden-brown glass shell with fine lines, glides slowly, no flagella: Navicula (a diatom). Has flagella: go to 6.
  6. A ball of hundreds of green cells that rolls: Volvox. A single cell: go to 7.
  7. Armoured plates and a groove around its middle; spins as it swims: Peridinium (a dinoflagellate). No plates: go to 8.
  8. Spindle-shaped, one long flagellum, a red eyespot, bends its body: Euglena. Oval and tiny (about 10 µm), two equal flagella, cup-shaped chloroplast: Chlamydomonas.

Simplifications: field of view width = 180,000 µm ÷ magnification (a typical student microscope). Sizes are typical adult sizes. Swimming is slowed to about one tenth of real speed so you can follow cells. Contractile vacuole rate is modelled as proportional to the difference between the cell's solute level (taken as 120 mOsm) and the water outside, about 10 pumps a minute in pond water; real rates vary by species and temperature.