| Illustrations by Caroline
Stromberg
Photographs © Botanics
Flowering plants’ showy petals are petals are
thought to be modified stamens which attract insects,
birds and other pollinators. Today, flowering plants
are extremely diverse; they even inhabit the water (duckweed)
and the air (Spanish moss). Some flowering plants are
parasitic and even carnivorous! Grasses, which today
cover 30% of the Earth’s land surface and provide
humans with more than 50% of the carbohydrates we eat
(think of corn, rice, bread, cereal…) did not
evolve until the latest Cretaceous.
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The earliest flowering plants are thought to
have been weedy shrubs that lived alongside
streams. One of these early groups to evolve
was the water lily family.
- Magnolias
Magnolias (Magnoliales) were among
the first groups of flowering plants to evolve.
Fossils of Magnolia-like plants are known from
early-mid Cretaceous sediments (Aptian-Albian,
~112 Ma) in North America. Because Magnolia,
and many other early flowers have large bisexual
flowers with very many floral parts (carpels,
stamens) compared to later (more “derived”)
groups of flowering plants, it was long thought
that this represented the “primitive”(ancestral)
condition from which other flower types evolved.
Now we know that both very large flowers with
numerous parts (such as Magnolia,) and simple
flowers with few floral parts, existed among
the earliest flowers.
Magnolia
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Paleontologists have suggested
a few explanations for why flowering plants evolved
at the end of the dinosaur era (~140 Ma):
- the environment during the Cretaceous –
which was warm and dry – favored the evolution
of flowering plants
- flowering evolved in conjunction with plant-eating
dinosaurs
- flowering plants evolved in conjunction with
insects
It is also possible that flowering plants DID
evolve earlier than the late Mesozoic, but the
plants were so small and fragile they didn’t
fossilize.
Unfortunately, none of these hypotheses
are well supported.
For a complete species
list in Project Exploration's Garden,
Click Here |
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