Biology / Unit 10 Bio 2185 short lesson, about 20 seconds
Seed Evolution: Three Key Innovations
Captions available
The idea
The seed habit combines three innovations: heterospory, per Bio 2181, an ovule protecting the megaspore, and pollen replacing swimming sperm.
In practice
Pollen carries sperm to an ovule without standing water, freeing seed plants from the fertilization constraint bryophytes and ferns face.
Where people slip
A seed is not a mere spore with a shell — it is a fertilized embryo packaged with stored food.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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