Plantae Phyla
Bryophytes
Commonly called mosses, they are green and photosynthetic
when young but tan or brown when ready to release spores. Dominated by the gametophyte
phase, they are usually under 15 centimeters tall. They lack a vascular system,
which prevents long-distance water and nutrient transport, explaining their
small size. Bryophytes also reproduce via spores, and not seeds. Their sporophyte
phase remain attached to the parental gametophyte, where they receive water,
sugars and other nutrients. Bryophytes are found in wet environments, as their
sperm require a film of moisture to reach the egg. An example is Marchantia, a liverwort.
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Lycophyta
Lycophytes
are found in many places, from on tropical tress, to the grounds of temperate
forests and finally underground. When on other plants, they are not parasitic.
And when underground, they form symbiotic relationships with fungi to
compensate for the lack of sunlight. While they remain seedless and use spores,
Lycophytes have vascular systems, allowing their sporophytes to have upright
stems with many small leaves. An example is Lycopodiella inundata.
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Pterophyta
Pterophytes, also called ferns, are seedless vascular
plants. They thrive in the tropics, temperate forests and some ferns can
survive in arid environments. While they release spores like Lycophytes, they
are more closely related to seed plants. Pterophytes have over-topping growth, megaphyll
(branched vascular system) leaves and roots that branch at various points. Their
dominant sporophytes have horizontal stems with long leaves, called fronds. Some
ferns may produce a trillion spores in its lifetime. An example is Athyrium filix-femina.
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Cycadophyta
Cycads
are limited today, but thrived during the Mesozoic era, at the same period of
the dinosaurs. They live in the subtropical and tropical regions of the world. These
gymnosperms have large cones and palm-like leaves. Their seeds contain a
neurotoxin which is reported to have killed scores of early European explorers. An example is Cycas rumphii.
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Ginkgophyta
Only one species of this gymnosperm survives to this day,
the Gingko biloba. It has deciduous
fan-like leaves, which turn a golden hue during autumn. The Gingko tree is
mainly found in Asia, but is a popular ornamental tree for cities, as it
tolerates air pollution well. Their branches bear fleshy seeds, known to emit a
rancid odor. There are pollen-only producing Gingko trees, which are more
popular due to their lack of rancid odor. The only example is the Maidenhair (Gingko biloba) tree.
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Coniferophyta
The largest of the gymnosperm phyla, conifers are dominant
in the Northern hemisphere. Some are cypresses and redwoods, but most are evergreens.
Evergreens keep their leaves throughout the year, allowing them to perform
limited photosynthesis during the winter, when the sun is out. When spring
arrives, their leaves are already developed and ready for photosynthesis. An example is the Northern conifer.
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Anthophyta
Called flowering plants, angiosperms are unique for their
flowers, double fertilization and fruits. Their flowers serve as the primary
structure for sexual reproduction. Pollen is produced in the stamen, and moved
by wind, insect or other modes of transportation to the stigma. Two sperm then
travel to the ovary. One merges with the ovule to create the zygote while the
other merges with polar nuclei to create an endosperm. The ovary matures into a
fruit which helps protect the embryo and aid in dispersal. Flowering plants are
found almost in every habitat where water and nutrients are present. An example is the Sweetbay Magnolia.
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Click on the following link to learn about the Anthophyta Classes: