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Introduction to Plants
The First Plants
 The earliest photosynthetic organisms
were plant-like protists.
 Even today about 70% of photosynthesis
occurs in the oceans.
Non-vascular Plants
 The earliest land plants
were non-vascular plants.
 Non-vascular plants have
no system of vessels to
carry nutrients, water or
waste.
 These mosses, liverworts,
and hornworts evolved
about 500 mya from
green algae.
Non-vascular Plant
Reproduction
 They need a moist surface
for gametes to swim
together for reproduction.
 Non-vascular plants lack
true leaves, roots or stems.
 All water, nutrients and
waste move between cells
by osmosis and diffusion.
Their growth is limited.
Plant Adaptations to Land
The major adaptations to life on land included:
1. Protection from drying out – leaves and stems.
2. A system of vessels
to transport water,
nutrients and wastes –
the roots, stems and
leaves.
3. A system to hold the
plant up and capture
energy from light – the
stem and leaves.
Vascular Plants - Ferns
 As plants adapted to land they
evolved more complex
structures.
 Ferns were the first vascular
plants.
 Ferns have vascular tissue or
vessels that transport
materials between different
parts of the plant.
 Ferns have true roots to anchor them
and absorb water and minerals.
 Fern leaves are photosynthetic and
absorb gases from the atmosphere.
Plants with Seeds
 Next plants evolved to have seeds, an
evolutionary adaptation to improve
reproductive success.
 Seeds allow a plant to reproduce
sexually without needing water for the
gametes to swim to each other.
Gymnosperms
 Gymnosperms are
plants that produce
“naked seeds”.
 Gymnosperms
include all the
conifers or pine
trees that produce
cones.
Angiosperms
 The most recent
evolutionary adaptation
for plants was to produce
flowers, again to improve
reproductive success.
 Angiosperms are
flowering plants.
 The seeds of
angiosperms are
protected in the body of a
fruit, which develops from
the ovary .
Links
http://www.teachersdomain.org/asset/oer0
8_vid_flowers/
http://www.teachersdomain.org/asset/tdc02
_img_insideseed/
http://www.teachersdomain.org/asset/lsps0
7_int_seedplant/