Biology / Unit 11 Bio 2523 short lesson, about 20 seconds
Annual Rings
Captions available
The idea
An annual ring forms from the contrast between spring wood's wide, thin-walled cells and denser, thick-walled autumn wood produced later the same year.
In practice
Counting a cross-sectioned trunk's rings estimates a tree's age; ring width and density also vary with that season's climate.
Where people slip
A ring records one season's growing conditions, not a fixed clock — width varies with rainfall and temperature, not age.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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