Choosing the Right CBSE School A Comprehensive Guide for Parents
Diversity in plants
1. WHAT IS DIVERSITY ?
Diversity is a commitment to
recognizing and appreciating the
variety of characteristics that make
individuals unique in an
atmosphere that promotes and
celebrates individual and collective
achievement.
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2. PLANTAE
The first level of classification among plants depends
on whether the plant body has well- differentiated,
distinct components. The next level of
classification is based on whether the
differentiated plant body ha special tissues for the
transport of water and other substance within.
Further classification looks at the ability to bear
seeds and whether the seeds are enclosed within
fruits.
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3. THALLOPHYTA
A phylum of plants of very diverse habit and structure, including
the algae, fungi, and lichens. The simpler forms, as many
blue-green algae, yeasts, etc., are unicellular and reproduce
vegetatively or by means of asexual spores; in the higher
forms the plant body is a thallus, which may be filamentous or
may consist of plates of cells; it is commonly undifferentiated
into stem, leaves, and roots, and shows no distinct tissue
systems; the fronds of many algae, however, are modified to
serve many of the functions of the above-named organs. Both
asexual and sexual reproduction, often of a complex
type, occur in these forms. The Thallophyta exist almost
exclusively as gametophytes, the sporophyte being absent or
rudimentary. By those who do not separate the Myxophyta
from the Tallophyta as a distinct phylum the latter is treated
as the lowermost group in the vegetable kingdom.
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5. BRYOPHYTA
A member of a large group of seedless green plants
including the mosses, liverworts, and hornworts.
Bryophytes lack the specialized tissues xylem and
phloem that circulate water and dissolved nutrients
in the vascular plants. Bryophytes generally live on
land but are mostly found in moist environments, for
they have free-swimming sperm that require water
for transport. In contrast to the vascular plants, the
gametophyte (haploid) generation of bryophytes
constitutes the larger plant form, while the small
sporophyte (diploid) generation grows on or within
the gametophyte and depends upon it for nutrition.
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7. PTERIDOPHYTA
A large group of higher plants to which are sometimes
assigned all higher seedless plants except mosses
(Bryophyta). Unlike the bryophytes, the sporophyte—the
asexual generation—is well developed and divided,
except in Psilotophyta, into stems, leaves, and roots.
Spores develop, from which emerges the gametophyte—
the sexual generation. The gametophyte is poorly
developed, almost undifferentiated, and bears sexual
organs (in males, antheridia, and in females,
archegonia). After fertilization, another asexual
generation develops.
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9. GYMNOSPERMS
Gymnosperms are a group of vascular
plants whose seeds are not enclosed by a
ripened (fruit). Gymnosperms are distinguished
from the other major group of seed plants,
the angiosperms, whose seeds are surrounded by
an ovary wall. The seeds of many
Gymnosperms (literally, naked seed) are borne
in cones and are not visible. Taxonomists now
recognize four distinct divisions of extant
gymnospermous plants (coniferophyta, cycadophyta,
ginkgophyta, and gnetophyta).
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11. ANGIOSPERMS
Any of a large group of plants that produce flowers.
They develop seeds from ovules contained in ovaries,
and the seeds are enclosed by fruits which develop
from carpel's. They are also distinguished by the
process of double fertilization. The majority of
angiosperms belong to two large classes :
monocotyledons and eudicotyledons. The
angiosperms are the largest phylum of living plants,
existing in some 235,000 species. They range from
small floating plants only one millimeter (0.04 inch)
in length to towering trees that are over 100 meters
(328 ft) tall.
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