Taxis steers. Kinesis changes speed or turning.
- The idea
- Predict
- See it
- Why
- Check
The idea
“Animals that gather near a stimulus must have aimed for it, whether by taxis or kinesis.”
You see woodlice bunched in the damp corner and picture them heading for it. They can get there without aiming.
The short version
The mistake: Animals that gather near a stimulus must have aimed for it, whether by taxis or kinesis.
What's actually true: A taxis is steered toward or away from a stimulus. A kinesis changes speed or turning with no aim, and it can gather animals too.
- A taxis is movement steered toward or away from a stimulus. Euglena swimming toward light and fly maggots crawling away from it are phototaxis.
- A kinesis changes how fast an animal moves or how often it turns, in no set direction.
- Both can gather animals, so where they end up won't tell you which it was.
- Switching from moving toward light to moving away is still taxis. The paths are still aimed.
On the exam: Check the paths. Aimed means taxis. Random headings with a change in speed or turning mean kinesis.