Page 147 - Biology_F5

Biology for Advanced Level Secondary Schools

Traditionally, bryophytes were classified (g) They are found mainly in damp and
into two classes, namely Musci and shady environments because their sexual
Hepaticae. Members of class Musci include reproduction depends on water, which
moss plants (Funaria sp.), while members facilitates mobility of their sperms.
of class Hepaticae include liverworts (Pellia (h) Asexual reproduction is by fragmentation
sp.). A recent classification splits bryophytes in which a small part of gametophyte can
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into three classes, namely Hepaticopsida detach from the mother plant to form a
(Liverworts), Bryopsida (Mosses), and new plant. In addition, green multicellular
Anthoceropsida (Hornworts). reproductive bodies of different shapes

called gemmae formed in gemma cups
General characteristics of division on the gametophyte can germinate to
Bryophyta form a new gametophyte upon falling
(a) They show alternation of generations on a suitable substrate.
in which the haploid gametophyte
generation is dominant over the diploid (i) They contain photosynthetic pigments
sporophyte generation. (chlorophyll) similar to that of higher
plants.
(b) The sporophyte is attached on the
gametophyte generation, and it depends
upon it for support and nutrition. Distinctive features of division
Bryophyta
(c) The gametophyte generation is Bryophytes possess the following features
anchored by filamentous rhizoids, which differentiate them from members
which provide support and used for of other divisions:
absorption of water and mineral salts.
(a) They lack conducting tissue such as
(d) They lack vascular tissues, meaning
that they have no xylem and phloem. xylem and phloem.
(b) They do not possess true stem,
(e) They have a thallus body, which shows leaves, and roots. They have rhizoids
low level of differentiation; hence, instead of roots and they also lack
they lack true leaves, stems, and roots. cuticle; therefore, absorption of water

(f) They have a sporophyte generation, and mineral salts in species such as
which produces homospores. Upon liverworts takes place over the whole
landing on a conducive environment, surface of the plant by diffusion.
the spores can germinate to form (c) They have a dominant gametophyte
the gametophyte generation on generation, on which sporophyte
which male and female reproductive generation is attached and depends on
structures develop. They undergo gametophyte for food and support.
sexual reproduction which involves (d) They are homosporous and their
multicellular sex organs called haploid spores germinate into
antheridia (male sex organs) and a characteristic structure called
archegonia (female sex organs). protonema, which are filament of cells
that later grow to form gametophytes.

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