Order V: Zygnematales

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Questions and Answers

What is unique about the structure of unicellular forms in the family Desmidiaceae?

They are cylindrical in shape

They are composed of two mirror-image semi-cells (correct)

They have multiple nuclei

They are always filamentous

What surrounds the filaments in the family Zygnemataceae?

A chloroplast

A slimy sheath (correct)

A nucleus

A cell wall

What is the shape of the chloroplasts in the genus Spirogyra?

Different shapes according to the genus (correct)

Spiral

Cylindrical

Circular

Where does Spirogyra typically occur?

In stagnant or slowly running waters Signup and view all the answers

What is unique about the chloroplasts in Spirogyra cells?

They have many pyrenoids each Signup and view all the answers

How does Spirogyra reproduce?

By vegetative fragmentation or sexual conjugation Signup and view all the answers

What is the growth pattern of the main axis in Chara?

Apical and unlimited Signup and view all the answers

What is the intermediate stage that arises from a germinated zoospore?

Protonema Signup and view all the answers

What is the characteristic of the rhizoids in Chara?

Filamentous, uniseriate, devoid of chloroplasts, and branched Signup and view all the answers

What is the arrangement of cells in a node in Chara?

Uninucleate cells surrounded by 6-20 cells Signup and view all the answers

What is the characteristic of the chloroplasts in Chara?

Many, ellipsoidal, and streaming in the peripheral cytoplasm Signup and view all the answers

What is the orientation of the rhizoids in Chara?

Positively geotropic, growing downward Signup and view all the answers

What is the classification of Chara?

Division Charophyta, Class Charophyceae, Order Charales Signup and view all the answers

What is the life cycle pattern of Chara?

No asexual life cycle Signup and view all the answers

What is the function of Amylum stars, bulbils, and tubers?

To withstand adverse environmental conditions Signup and view all the answers

What is unique about the Antheridium?

It's surrounded by a wall with shield cells Signup and view all the answers

What is the function of the pedicel?

To support the Antheridium Signup and view all the answers

How many cells are in the primary capitulum?

8 Signup and view all the answers

What happens to the shield cells when the Antheridium matures?

They separate to expose the antheridial filaments Signup and view all the answers

What is the arrangement of tube cells in the Oogonium?

Helical Signup and view all the answers

What happens to the zygote after formation?

Its wall thickens and it rests for a period Signup and view all the answers

What is the result of meiosis in the zygote?

Formation of primary protonema Signup and view all the answers

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 Signup and view all the answers

What is the composition of the cell wall in Cladophora?

Chitin, pectin, and cellulose Signup and view all the answers

What is the characteristic of the life cycle of Cladophora?

Isomorphic alternation of generations Signup and view all the answers

What is the function of the gametangium in Cladophora?

To produce gametes Signup and view all the answers

What is the characteristic of the diploid filament in Cladophora?

It has 2N number of chromosomes Signup and view all the answers

What is the type of conjugation where the contiguous ends of papillae dissolve, forming a conjugation canal?

Scalariform conjugation Signup and view all the answers

What is the characteristic of the storage food materials in Charophytes?

Starch and cellulose Signup and view all the answers

What is the characteristic of the reproductive units in Charophytes?

They are motile with two equal sub-apical flagella Signup and view all the answers

What is the term for the process where the protoplast of apical or sub-apical cells breaks into uninucleate segments?

Zoospore formation Signup and view all the answers

What is the characteristic of the haploid individual in Cladophora?

It reproduces sexually Signup and view all the answers

Study Notes

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

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Description

This quiz covers the characteristics of Zygnematales, a type of freshwater algae, including their unicellular and filamentous forms, and classification into different families.

Order V: Zygnematales - Freshwater Algae

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