The Red Queen Hypothesis

Activities to try

1. 1

   Drive the arms race: run a two-population co-evolution model

   Why it works: In the model, because each improvement by one partner is answered by the other, both trait values escalate together while the relative gap stays roughly constant — so a species must keep evolving just to hold its position. This escalation is a directionless response to a co-evolving partner, not progress toward a 'better' or 'perfect' organism. As long as the partner keeps evolving, there is no fixed finish line, although in real species an arms race can slow or stop because of costs and physical limits, or end if one species dies out.

   1. Open a model of two coupled populations (e.g. cheetahs and gazelles) where selecting for a trait in one population feeds back as selection pressure on the other.
   2. Apply selection to ONE partner only — breed faster cheetahs — and watch a live graph of both trait means over generations plus the other partner's fitness.
   3. Observe the gazelles' fitness drop, then claw back as faster gazelles are now favoured, so their trait mean rises too.
   4. Keep pushing one side repeatedly and describe what happens to the GAP between the two trait curves as both climb.
   5. Optionally relate the pattern to a 'moving escalator' image — running just to stay in place as the background scrolls — to capture the slogan.
2. 2

   Parasite-host cycling with fast generations

   Why it works: Fast parasite generations let co-evolutionary cycling be seen on a comprehensible timescale: rare host genotypes gain a temporary edge because parasites are tuned to the common type, so advantage keeps shifting and no genotype wins permanently. This requires standing genetic variation — several genotypes present, one common at a time.

   1. Switch to (or examine) a parasite-host scenario where parasites reproduce much faster than hosts.
   2. Start with a host population containing several genotypes, one of which is initially common, and track their frequencies over many generations.
   3. Observe how parasites adapt to attack the common host type, giving an advantage to whichever host genotype is currently rare.
   4. Describe the resulting cycle: common genotype → parasite tracks it → rare genotype now favoured → frequencies shift → cycle repeats.
   5. Explain in your own words why no single host genotype stays best forever.
3. 3

   Mutualism and prediction: the orchid and the hawk moth

   Why it works: Co-evolution is not only conflict: in a mutualism each partner shapes the other's traits, producing matched features. A reciprocal relationship can be close enough to let scientists forecast an unknown partner — Darwin's long-tongued hawk moth prediction was later confirmed.

   1. Examine an illustration of an orchid with a long nectar spur and the matching tongue length of its moth pollinator, with Darwin's prediction annotated.
   2. Measure (or read off) the depth of the orchid's nectar spur.
   3. Use the length-matching relationship to 'predict' the tongue length of an unknown moth pollinator, as Darwin did before the moth was found.
   4. Explain why co-evolution can produce such a tight match between two partners that benefit each other.
   5. State how this mutualistic case differs from a predator-prey arms race while still being reciprocal co-evolution.