12b. Spirogyra.pptx

Spirometer

1. Spirogyra

2. CONTENTS Introduction Habitat
Thallus structure
Cell structure
Movement
Growth
Reproduction

3. Member of division Chlorophyta , also called green algae Derived from two Greek words: Speria (meaning coil) and gyras (meaning twisted); named after spirally arranged chloroplasts in cell Looks like a mass of long shining silky filaments in running water, that is why it is called pond silk

4. Habitat Widely distributed and found throughout the world It commonly grows in fresh water including stagnant reservoirs , slow running streams and rivers It grows as free-floatin g mass, so it is commonly called pond scum Suitable season for its growth is spring, but it grows well throughout the year It develops reproductive stage if temperature rises and develops vegetative stage if temperature lowers

5. Thallus structure Plant body consists of green -colored filaments Filaments are unbranched, measuring approximately 10 to 100μm in width and may grow up to several centimeters in length Individual cells in a filament are cylindrical (much longer than broad) and joined end to end No distinction between basal and distal ends in free-floating species Attached forms have modified basal cells called hapteron or holdfast

6. Cell structure Cell wall : Consists of three layers ; with inner two layers made of pectin and outer layer composed of cellulose. The slimy mucilaginous sheath surrounding the filament of Spirogyra cell is formed due to the dissolution of pectin in water and is slippery to touch.

7. Cell Membrane: Situated just beneath the cell wall, it is selectively permeable in nature that protects the inner cell content from the outside environment. Cytoplasm: Mostly distributed to the periphery of cell, forming thin lining along the cell wall. It contains most other organelles such as endoplasmic reticulum, Golgi bodies, mitochondria, ribosomes, and other cytoplasmic inclusions. It is traversed by several cytoplasmic strands. Vacuole: A centrally located large organelle that is filled with fluid, and maintains the water and salt balance inside the cell. The vacuole is separated from the surrounding cytoplasm by a semi-permeable membrane called tonoplast.

8. Chloroplast: A ribbon-shaped organelle that is arranged spirally. It contains the green pigment chlorophyll that helps them to perform photosynthesis for producing their own food. There are approximately 1 to 16 chloroplasts present in a typical Spirogyra cell. A dense, highly refractive, granular protein body called pyrenoids is found within the chloroplast at very short intervals. Pyrenoids helps the cell to store starches and proteins, also providing a distinctive identifiable feature to Spirogyra. Nucleus: A membrane-bound organelle that contains the genetic material of the cell. The nucleus resides at the center of the cell, being supported by the cytoplasmic strands. It also contains a distinct nucleolus that helps the cell to synthesize proteins.

9. Movement Spirogyra  forms long filaments that are capable of bending, twisting and straightening their filaments, enabling locomotion Move slowly in the liquid medium Also move towards light sources (which they need for photosynthesis)

10. Growth Growth take place by cell division of any cell of the filament

11. Reproduction Broadly Spirogyra perform three modes of reproduction  Vegetative reproduction is common Asexual reproduction is rare mode, only exhibited by some species Sexual reproduction is also common

12. Fragmentation is the common method, when favorable environmental conditions, water and nutrients are available Accidental breaking or injury may occur It breaks the filament into 2-3 cell portions Each portion germinates to produce a new plant Vegetative Reproduction

13. Asexual Reproduction Akinetes: When environmental condition become harsh, some vegetative cells of filament lose water get shrunk and rounded. They deposit thick wall and act as resting spore. On return of favorable condition, akinete germinate into new filament. Aplanospore: Vegetative cell after losing water get rounded up, secrete thin wall around and develop into spore. Single aplanospore formed in single cell. Aplanospore are released after decay of mother filament and germinate into new filament on arrival of favorable condition Azygospore : It is also known as parthenospore . In some species, due to physiological condition gametes fail to fuse and behave as spore.

14. Sexual Reproduction Isogamous type: Spores of similar size fuse to form new filaments Takes place by conjugation Entire protoplasmic contents of vegetative cells (viz., gametangia) function as gametes Two types: Scalariform and Lateral conjugation

15. Scalariform conjugation Common method Occur between two filaments of different physiological strains (heterothallic)

16. Two filaments come close, lie opposite and parallel to each other held in mucilage Opposite cells of both filaments develop outgrowths called protuberances At the point of contact, tips of protuberance dissolve to form conjugation tube between opposite cells When conjugation tube is forming, protoplasts of conjugating cells (gametangia) recede, round up and function as gametes Male gametes transfer through the conjugation tube into opposite cell (female gametangia) and fuse with female gamete to form zygote (2n) Zygote secretes a thick wall to become zygospore Therefore, in the late stage of conjugation, male gametangia remain empty and the female gametangia contain zygospores Due to several conjugation tube formation between two filamentous cells, its appearance is like a ladder. Hence, it is called scalariform (Greek, scala = ladder; forma = shape) or H-shape conjugation.

17. Lateral Conjugation Rare occurrence Involves the fusion of gametes from two adjacent cells of the same filament Occur in monoecious or homothallic species Indirect lateral conjugation Two outgrowths emerge on both side of a transverse septum of two adjunct cells and after some growth the two protuberances unite to form a conjugation tube Of the two adjacent cells, one behaves as male gametangium whiles the other as female gametangium

18. The content (now behaving as gamete) from male gametangium passes through conjugation tube and enters into female gametangium By the fusion of male and female gametes a diploid zygospore is formed Thus, in each second cell of a filament, a zygospore is formed Direct lateral conjugation In this type of conjugation, male gametangium after passing through an aperture in the transverse septum of adjoining gametangium enters the female gametangium It fuses with female gamete, and diploid zygospore is formed

19. Zygospore Germination Zygospore is the only diploid phase in sexual life cycle Decay of female gametangia causes liberation of zygospore which remains dormant in pond bottom On return of favorable condition, diploid nucleus of zygospore undergo meiosis to produce 4 haploid nuclei out of which 3 degenerate Zygospore with one haploid nucleus gradually enlarges and burst open to release a germ tube Repeated transverse divisions of germ tube form a new filament

20. Life Cycle Haplontic life cycle , with no true alternation of distinct plants Rather, alternation of chromosome numbers from haploid to diploid and back to haploid conditions can be noticed Involves haploid vegetative filament (gametophyte) and a diploid zygospore, towards the end of growing season Gametes fuse to form a zygospore (2n) Zygospore gives rise to a haploid new filament

21. Reference https://biologywise.com/what-is-spirogyra https://www.onlinebiologynotes.com/spirogyra-habitat-structure-reproduction-and-germination-of-zygospore/ https://unacademy.com/content/neet-ug/study-material/biology/the-concept-of-spirogyra/ https://www.vedantu.com/neet/spirogyra https://biologyboom.com/type-spirogyra-only-for-b-s/ https://www.sciencefacts.net/spirogyra.html https://www.seaweed.ie/algae/spirogyra.php https://www.chegg.com/learn/biology/introduction-to-biology/spirogyra https://botnam.com/life-cycle-of-algae/