5 DIAGNÓSTICO
5.2 La estructura organizativa de la Unidad Educativa
5.2.3 Funciones por áreas y departamentos
The green algae probably evolved from motile unicells similar to
Chlamydomonas.It exhibits a variety of forms and it has different reproduction.
This group presents a clear example of radiating evolutionary development. The evolution of sexuality has been emphasised because of the great importance of this type of reproduction in the production of variation which is significant in the survival of any group.
Green algae are also thought to have given rise to all of the higher green plants by evolution.
The chloroplast in both fresh and salt water comprise food supplies for animals.
Algae (e.g. ulva) are utilised by mains food
The photosynthetic process of algae supplies the oxygen that is necessary for life in water.
Green algae along with other algae, occassionally cause problems when they become abundant in water. They impart obnoxious odours and flavours to the water, and make water treatment difficult.
Algae have a lot of significant importance to man and his environment. Therefore, their study should be intensified
In this unit, you have learned that;
i.
Algae are cryptogams.
u.
They are simple plants without roots, stems and leaves.
iii. The cell wall of algae is composed of cellulose.
iv. The reserve carbohydrate is usually starch and not glycogen as in fungi.
v. Algae can undergo both sexual and asexual reproduction.
vi. Algae are important to man and his environment.
i. Briefly explain the importance of algae to man and his environment
ii. List five attributes which show that both
Amoebaand
Spirogyraare living organisms.
Dutta A. C. (1979)
Botany for Degree Students -Oxford University Press, Dehli Bombay, Madras
Sarojini T. Ramalingam (1993)
Modern Biology- Africana - Feb Publishers, Onitsha.
Idodo - Umeh G (1996).
College Biology -Idodo - Umeh Publishers Benin City
Page
1.0 Introduction 71
2.0 Objectives 71
3.0 Characteristics of Mosses 71
3.1 Reproduction in Mosses 73
3.1.1 Antheridium 73
3.1.2 Archegonium 73
3.1.3 Gametophyte 73
3.1.4 Sporophyte 74
3.1.5 Alternation of Generations 74
3.2 Economic Importance of Mosses 75
3.3 Differences Between Fungi and Mosses 75
3.4 Similarities Between Fungi and Mosses 76
4.0 Conclusion 76
5.0 Summary 76
6.0 Tutor - MarkedAssignment 76
7.0 Further Readings and other Resources 76
70
Mosses 71
Mosses belong to the division Bryophyta and the class,
musci.Mosses are land plants which grow on moist ground under the shade of big trees as epiphytes; on packed wet blocks, and or old block walls and rocks.
Funaria(a common moss species) grows in turfs to form a green carpet. Sometimes, relatively extensive areas may be completely covered by it, particularly the sites of old bonfires in woodlands. The moss is often able to colonise such burnt patches remarkably quickly. This is an indication of its measure of success as a land plant. Mosses lack true roots, stems and leaves; they are parenchymatous (i.e. they have parenchyma tissues), they lack vascular tissue. The gametophyte (the haploid, gamete producing phase of the plant) is dominant and nutritionally independent, whereas the sporophyte (the diploid, spore-producing phase of the plant) is permanently attached to the gametophyte.
The mature gametophyte is usually erect and radially arranged. The spores are released from the sporophyte by a tranverse splitting of the sporangium or capsule.
Mosses play an important role in nature as we shall see....
By the end of this unit, you should be able to;
i. List at least ten of the general characteristics of mosses.
ii. Describe the process of reproduction in
Funaria(moss).
iii. List at least five differences between Fungi and Mosses.
iv. Trace the link between simpler plants (unicellular forms) and complex, more advanced plants (multicellular forms).
Do you remember that living organisms have some characteristics or features that are peculiar to them?
Mosses as living organism have their peculiar characteristics. See the following characteristic features of mosses below;
The plant is small and erect.
Persisting vegetative body is attached to subsratum.
Body consists of attaching and absorbing rhizoids and, aerial part for photosynthesis.
Dichotomous branching.
Growth is from a single cell or row of cells.
Low degree of tissue differentiation.
Well defined sexual reproduction.
Sex organs are the antheridia and archegonia.
Fertilisation is with biflagellate male gametes.
Plant body is one haploid gametophyte.
Diploid sporophyte (sporogonium) is partially or wholly dependent upon the gametophyte.
Spores are of one type (homosporous)
Spores usually germinate into an intermediate structure (protonema).
Mainly terrestrial but in wet environment.
Commonly found on old damp walls, tree trunks and wet ground.
They are gregarous, forming green carpet.
Small in size measuring a little more than one centimeter in height.
Axis is short with spiral, minute green leaves.
True roots are absent but rhizoids are present for absorption and anchorage.
Rhizoids are made of cells not differentiated into tissues and organs.
The stem (no conducting tissues) is short, slender and often with a branching stem, covered by
remains of archegonial neck
rosette of leaves at tip of male shoot
cluster of leaves at tip of female shoot; surround archegonia (female sex organ) 'leaf' - well developed with conspicuous midrib; leaves spirally arranged
'stem
capsule - photosynthetic;
green when immature, orange-brown when ripe annulus - cells here force off operculum when capsule is ripe operculum - lid of capsule sporophyte
semi-dependent on gametophyte
simple leaves spirally arranged along the stem and its branch.
The two branches of stem are differentiated into male and female branches.
The sporogonium consists of a long seta (stalk) and a pear-shaped capsule.
The rhizoid, stem and leaves all together form the gametophyte. The gametophyte alternates with the sporophyte during the life cycle. This is called alternation of generations.
Now, you may wish to know the structure of a moss plant. See below
mature capsule
annulus (lid detached)
peristome - two rows of teeth on which open out in dry. xonditions /' allowing release of spores spores
calyptra - remains of archegonium; covers
antheridia-(male sex capsule during development, later falling
off
rhizoids multicellular
Figure 9.1: Features of a Moss Plant
organs)
MOSS. A, Three moss plants with capsule; B, Apex of the male shoot in L.S. showing antheridia (AN), paraphyses (P) and leaves (L); C, a mature antheridium discharging antherozoid mother cells in a mass of mucilage (A), antherozoid mother cell (B), wall of the same getting dissolved (C), and biciliate antherozoid (D).
Mosses 73
Study the diagram illustrated in fig. 9.1 and use it to list six features of a moss 3.1 Reproduction in Moss
You will find reproduction in moss very interesting. Would you like to know how reproduction occurs in moss plant?
The moss plant (e.g.
Funaria)bears separate male and female parts at maturity, biciliate spermatozoa
(antherozoids)