origin of plants/seeds
mbleeker at euronet.nl
Thu Jun 8 02:04:00 EST 1995
In article <3r4llg$3og at senator-bedfellow.MIT.EDU> laura van dam <lvandam at mit.edu> writes:
>From: laura van dam <lvandam at mit.edu>
>Subject: origin of plants/seeds
>Date: 7 Jun 1995 16:55:12 GMT
>I am a parent volunteer in Massachusetts teaching five- and six-year-olds
>in my son's kindergarten class about how to research on their own.
How the first seed was made ? Difficult question Ian ! First, there were
plants that had no seeds. Such plants still exist: ferns. They have no flowers
either. They just make spores on the leaves, billions of very little grains,
like dust. Each spore can grow out to become a new fern. But- and this is a
big but- it has to find water to start growing. Now there were some smart
ferns, who made bigger spores. They also still exist, like a kind of
tumbleweed in the desert (Selaginella). These large spores start growing
already inside, to become baby-ferns, while they are still on the mother
plant. This is a smart move, because the mother plant can give them the water
and shelter they need.
A seed is also a solution to living in dry places. All life came from the
water, and ferns are still very dependent on wet places for their
reproduction. The seed allowed plants to conquer drier parts of the land.
Nobody knows how and where it exactly evolved. For instance, we find fossil
fern leaves in charcoal. Or, we THOUGHT we found fossil fern leaves. But
later we found the same leaves, carring seeds... So we call those extinct
plants now 'Seedferns'. They were the first seed-plants, but we know very
little about them...
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