Spirogyra: Freshwater Green Algae

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Questions and Answers

What is the common name for Spirogyra?

Water silk

Green thread

Pond silk (correct)

Freshwater algae

What is the characteristic feature of Spirogyra's chloroplasts?

They are rectangular in shape

They are spherical in shape

They are triangular in shape

They are spiral in shape (correct)

What is the function of the central vacuole in Spirogyra cells?

To regulate cell growth

To maintain cellular turgor and buoyancy (correct)

To store genetic material

To synthesize proteins

What is the purpose of conjugation in Spirogyra's life cycle?

To fuse compatible filaments Signup and view all the answers

What is the result of meiosis in Spirogyra's life cycle?

Haploid zoospore production Signup and view all the answers

What is the byproduct of photosynthesis in Spirogyra's chloroplasts?

Oxygen Signup and view all the answers

What is the composition of Spirogyra's cell wall?

Cellulose and pectin Signup and view all the answers

How does Spirogyra reproduce asexually?

Through fragmentation Signup and view all the answers

What is the function of a gemma cup?

To produce a new plant Signup and view all the answers

What is the term for a multicellular, green, asexual bud?

Gemma Signup and view all the answers

What is the product of fertilization in mosses?

Zygote Signup and view all the answers

What is the largest class of Bryophyta?

Mosses Signup and view all the answers

What is the term for the haploid stage of the life cycle of mosses?

Gametophyte Signup and view all the answers

What is the function of elaters?

Not present in mosses Signup and view all the answers

How does the capsule of a moss sporophyte open?

By separation of the lid Signup and view all the answers

What is the term for the multicellular structures that anchor mosses to the substrate?

Rhizoids Signup and view all the answers

What is the role of Spirogyra in aquatic ecosystems?

Contributing to oxygen production, nutrient cycling, and serving as a food source Signup and view all the answers

What is the characteristic feature of Bryophytes?

Lack of lignin in specialized tissues Signup and view all the answers

What is the origin of the name 'Hepaticopsida'?

From the word 'hepatic' meaning liver Signup and view all the answers

What is the characteristic of the thalloid form of Hepaticopsida?

It is dorsiventral, lobed and dichotomously branched Signup and view all the answers

What is the function of rhizoids in Hepaticopsida?

To provide anchorage Signup and view all the answers

How do Hepaticopsida reproduce asexually?

By fragmentation or by the formation of gemmae Signup and view all the answers

What is the composition of the sporophyte in Marchantia?

Foot, seta and capsule Signup and view all the answers

What is the feature of the capsule in Hepaticopsida?

It lacks a columella Signup and view all the answers

Study Notes

Spirogyra

Spirogyra is a genus of filamentous green algae that belongs to the division Chlorophyta.
It is commonly found in freshwater environments around the world.
Spirogyras are unicellular organisms that grow in long, unbranched chains of cylindrical cells.
They have helical chloroplasts and unbranched filaments, playing a significant role in aquatic ecosystems.

Structure

Spirogyra exhibits a unique structure composed of unbranched filaments, each consisting of a single row of cylindrical cells.
Each cell is enclosed by a thin cell wall composed of cellulose and pectin, providing support and protection.
A large central vacuole occupies most of the space, maintaining cellular turgor and buoyancy.
Embedded in the cytoplasm is a prominent nucleus, responsible for genetic control.
Numerous spiral chloroplasts are present, containing chlorophyll, the pigment responsible for photosynthesis.

Life History

Asexual reproduction occurs through fragmentation, where portions of the filament break off and develop into new individuals.
Sexual reproduction occurs through conjugation, involving the fusion of two compatible filaments.
During conjugation, cells from adjacent filaments form conjugation tubes, allowing the contents of one cell to transfer into the other, forming a diploid zygote.
The zygote undergoes meiosis, producing haploid zoospores.
Gemmae are produced inside gemma cups, which are asexual buds that are green and multicellular.

Bryophytes

Bryophyta refers to embryophytes, which are land plants, especially the non-vascular ones.
This division includes mosses (class Bryopsida), liverworts (class Marchantiopsida), and hornworts (class Anthocerotopsida).
The only prime feature of a bryophyte is that it does not have true vascular tissue.
Bryophytes are believed to evolve from charophytes and are considered to have been the first true plants to have ever evolved.

Bryopsida (Mosses)

Bryopsida is the largest class of Bryophyta, with around 1400 species.
Examples of mosses include Funaria, Polytrichum, and Sphagnum.
Bryopsida is further divided into 5 orders: Bryales, Andreales, Sphagnales, Polytrichales, and Buxbaumiales.
The main features of Bryopsida include:
- Gametophyte is differentiated into protonema and foliose gametophore.
- Foliose is made up of stem as an axis and leaves without midrib.
- Rhizoids are multicellular with oblique septa.
- Sex organs are borne apically on stem.
- Elaters are absent.
- The sporophyte is differentiated into foot, seta, and capsule.
- Sporogenous tissues develop from endothecium.
- Columella is present.
- Dehiscence of the capsule takes place by separation of the lid.

Hepaticopsida (Liverworts)

Liverworts come under this class.
Hepaticopsida is further divided into 4 orders: Marchantiales, Sphaerocarpales, Calobryales, and Jungermanniales.
The main characteristics of the class Hepaticopsida are:
- Gametophyte plant is either thalloid or foliose.
- In foliose forms, leaves are without midrib and dorsiventral.
- Thalloid is dorsiventral, lobed, and dichotomously branched.
- Each cell of thallus contains many chloroplasts without pyrenoids.
- Rhizoids are unicellular, branched, and aseptate.
- Sex organs are borne dorsally embedded in gametophytic tissues.
- The sporophyte is made up of only capsule (in Riccia) or foot, seta, and capsule (in Marchantia).
- The columella is absent in the capsule.
- Sporogenous tissues develop from endothecium.
- Asexual reproduction takes place by fragmentation or by the formation of gemmae.