32 Questions
What is unique about the structure of unicellular forms in the family Desmidiaceae?
They are composed of two mirror-image semi-cells
What surrounds the filaments in the family Zygnemataceae?
A slimy sheath
What is the shape of the chloroplasts in the genus Spirogyra?
Different shapes according to the genus
Where does Spirogyra typically occur?
In stagnant or slowly running waters
What is unique about the chloroplasts in Spirogyra cells?
They have many pyrenoids each
How does Spirogyra reproduce?
By vegetative fragmentation or sexual conjugation
What is the growth pattern of the main axis in Chara?
Apical and unlimited
What is the intermediate stage that arises from a germinated zoospore?
Protonema
What is the characteristic of the rhizoids in Chara?
Filamentous, uniseriate, devoid of chloroplasts, and branched
What is the arrangement of cells in a node in Chara?
Uninucleate cells surrounded by 6-20 cells
What is the characteristic of the chloroplasts in Chara?
Many, ellipsoidal, and streaming in the peripheral cytoplasm
What is the orientation of the rhizoids in Chara?
Positively geotropic, growing downward
What is the classification of Chara?
Division Charophyta, Class Charophyceae, Order Charales
What is the life cycle pattern of Chara?
No asexual life cycle
What is the function of Amylum stars, bulbils, and tubers?
To withstand adverse environmental conditions
What is unique about the Antheridium?
It's surrounded by a wall with shield cells
What is the function of the pedicel?
To support the Antheridium
How many cells are in the primary capitulum?
8
What happens to the shield cells when the Antheridium matures?
They separate to expose the antheridial filaments
What is the arrangement of tube cells in the Oogonium?
Helical
What happens to the zygote after formation?
Its wall thickens and it rests for a period
What is the result of meiosis in the zygote?
Formation of primary protonema
What is the term for the type of reproduction where conjugation takes place between gametes produced in two adjacent cells of the same filament?
Lateral conjugation
What is the composition of the cell wall in Cladophora?
Chitin, pectin, and cellulose
What is the characteristic of the life cycle of Cladophora?
Isomorphic alternation of generations
What is the function of the gametangium in Cladophora?
To produce gametes
What is the characteristic of the diploid filament in Cladophora?
It has 2N number of chromosomes
What is the type of conjugation where the contiguous ends of papillae dissolve, forming a conjugation canal?
Scalariform conjugation
What is the characteristic of the storage food materials in Charophytes?
Starch and cellulose
What is the characteristic of the reproductive units in Charophytes?
They are motile with two equal sub-apical flagella
What is the term for the process where the protoplast of apical or sub-apical cells breaks into uninucleate segments?
Zoospore formation
What is the characteristic of the haploid individual in Cladophora?
It reproduces sexually
Study Notes
Order V: Zygnematales
- Freshwater algae, unicellular or filamentous forms
- Unicellular forms have unique structure, composed of two mirror-image semi-cells, classified in family Desmidiaceae
- Filamentous forms in family Zygnemataceae, unbranched, surrounded by slimy sheath, cells usually longer than broad
- Chloroplasts of different shapes, each with many pyrenoids
- Two genera: Spirogyra and Zygnema
Spirogyra
- Filaments cylindrical, slimy, called water silk
- Occurs in stagnant or slowly running waters
- One to many chloroplasts per cell, spiral coils occupy most cellular space
- Cells have single nucleus, attached to peripheral cytoplasm with cytoplasmic strands
- Reproduction: vegetative by fragmentation, sexual by conjugation
- Conjugation: filaments aggregate, papillae protrude, conjugation canal forms, gametes fuse, zygote forms and germinates
Order: Cladophorales, Family: Cladophoraceae, Genus: Cladophora
- Cells multinucleate, placed end to end
- Widely distributed, fresh or marine water habitat
- Filaments branched, branching lateral near upper end of cell
- Cell wall composed of chitin, pectin, and cellulose
- Reproduction: vegetative, asexual, and sexual
- Vegetative: fragmentation
- Asexual: protoplast breaks into uninucleate segments, transformed into quadriflagellate zoospores
- Sexual: apical or sub-apical cells produce biflagellate isogametes, fuse to form zygote
- Alternation of generations: diploid filament reproduces asexually, haploid individual reproduces sexually
Division IV: Charophyta
- Plants grass green due to presence of chlorophyll a, b, carotenoids, and xanthophylls
- Storage food: starch, chloroplasts with pyrenoids
- Cell wall: cellulose, individuals immotile, reproductive units with two equal sub-apical flagella
- Similarity to Chlorophytes, but more related to Bryophytes
- Thallus structure: erect axis, whorled branches, rhizoids, apical growth
- Zoospores germinate to form protonema
- Sexual organs complex, with sterile cells encasing them
- Classification: single class Charophyceae, order Charales, few genera (Chara, Nitella, Nitellopsis, Tolypella)
Order Charales, Genus Chara
- Freshwater, stagnant or slowly running water
- Thallus fixed to muddy bottom or stones via rhizoids
- Internode: one long multinucleate cell, surrounded by corticating cells
- Node: composed of uninucleate cells, two cells in center surrounded by 6-20 cells
- Apical cells lead to formation of branchlets in whorled fashion
- Chloroplasts: large number of ellipsoidal, streaming in peripheral cytoplasm
- Rhizoids: filamentous, uniseriate, devoid of chloroplasts, branched, positively geotropic
Reproduction of Chara
- No asexual life cycle, reproduces vegetatively and sexually
- Vegetative reproduction: formation of aggregates (Amylum stars, bulbils, tubers)
- Amylum stars: aggregates on lower nodes, filled with starch, star-like shape
- Bulbils: spherical aggregations on rhizoids
- Tubers: branched produced on certain nodes
- Each structure can withstand adverse conditions and give new plants
- Sexual reproduction: oogamy, monoecious, antheridia and oogonia on same plant
- Antheridium: globose, surrounded by shield cells, borne on stalk (pedicel)
- Oogonium: contains single ovum, surrounded by tube cells, supported by pedicel
- Fertilization: antherozoids from antheridium fertilize ovum, zygote forms and germinates
This quiz covers the characteristics of Zygnematales, a type of freshwater algae, including their unicellular and filamentous forms, and classification into different families.
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