Today we will discuss about the algae, which are Eukaryotic plants, my be microscopic single cellular or macroscopic multicellular. These are grouped under plants kingdom
- Autophytic nutrition.
Exception- Cephaleuros (a parasitic algae)
- Fresh water or marine
- Thallus body
- Reserve food material is starch
- Cell wall- cellulose
- True parenchymatous cells are present
- Microscopic or macroscopic
- Reproduction- vegetative, asexual and sexual
- Eg. Spirogyra, Volvox, Chlamydomonas, Chara etc
Q and A of Algae
- Distinguish between coenocyte and coenobium. (1)
|1. A mass of cytoplasm surrounding many nuclei and enclosed by a cell wall. It is found in certain algae and fungi.||1. A colony of Volvox is called coenobium.|
Mention few characteristics of (unicellular) Chlamydomonas.
a. Chlamydomonas is a unicellular motile green alga possessing two flagella and usually a cup shaped chloroplast.
b. Cell wall is thin and composed of cellulose.
c. The basal granules situated at the base of the flagella are called blepharoplasts.
d. At the base of each flagella lies one contractile vacuole, etc.
Mention few characteristics of Volvox (colonial).
a. The cells of the coenobium vary according to species and are mostly ovoid shaped.
b. The neuromotor organ of each cell is composed of blepharoplast, rhizoplast and centrosome.
c. The nucleus is connected with the neuromotor organ.
d. During the movement of colonial alga Volvox, the neuromotor organ controls the movement of the flagella, etc.
Mention few characteristics of Spirogyra (filamentous)
a. The plant body is unbranched, filamentous, green coloured, with cylindrical cell placed end to end.
b. In some sedentary species like Spirogyra adnata and Spirogyra jogensis the basal cell is modified to haptera or holdfast, which is the organ of attachment.
c. The lateral cell wall is stratified and three layered, the inner two layers are composed of cellulose and the outermost layer is composed of pectose. The cross wall is also three layered, the middle lamella is composed of pectose bounded on either side by layers of pectin.
d. Each cell bears a varying number of ribbon shaped, spiral, chloroplasts with either serrated or smooth edges, etc.
What is palmella stage? In which alga is it noted?
When Chlamydomonas sp. is left on the wet, moist banks of the ponds by the receding water or grows on damp soil, it forms palmella stage. In this stage, the daughter cell produced as a result of successive divisions of protoplast of the cell in nonmotile form remains embedded within the mucilagenous matrix formed due to gelatinisation of the parent cell wall. These daughter cells may divide and re-divide forming amorphous colony with hundreds and thousands of cells. Under favourable condition, i.e. when a palmella stage is flooded with water the cells develop flagella, become motile and escape from the matrix. Each cell develops into a new plant either by the formation of zoospores and aplanospores.
It is noted in Chlamydomonas braunii.
Define the following terms.
a) Isogamy b) Anisogamy c) Oogamy
a) Isogamy: When two morphologically identical biflagellate gametes are involved in the union and form a diploid zygote, it is called isogamy, it is noted in Chlamydomonas debaryana and Chlamydomonas eugametos.
b) Anisogamy: When fusion takes place between two morphologically nonidentical motile gametes and thereby form a diploid zygote, it is called anisogamy, it is noted in heterothallic species of Chlamydomonas braunii.
c) Oogamy: When fusion takes place between two dissimilar gametes and one is motile and another one is nonmotile, and thereby form a diploid zygote, it is called oogamy, it is noted in
Chlamydomonas coccifera and Chlamydomonas oogamum.
What are trichome and filament?
In case of filamentous algae, a single row of cells is called a trichome. When a trichome is surrounded by a gelatinous or mucilaginous sheath then it is called a filament.
Write which one is haploid and which one is diploid in Spirogyra?
a) Spirogyra b) Gamete c) Zygospore d) Azygospore (a thick-walled spore produced by parthenogenesis in certain algae and fungi)
a. Haploid, b. Haploid, c. diploid, d. haploid,
What is conjugation tube in Spirogyra?
Ans. Conjugation is the temporary union of two cells belonging to two different individuals of the same species. During this process one gamete moves through the conjugation tube and unites with the other to form a diploid zygospore (2n). The gametes uniting in this process, though being physically different in nature, are morphologically similar.
Name one marine alga and one symbiotic alga.
Ans. Laminaria and Zooxanthelli
Why blue green algae like Nostoc, Anabaena are considered as prokaryotic?
Ans. Algal cell is generally eukaryotic in nature, but may be prokaryotic. In case of blue green algae like Nostoc, Anabaena, etc. no well developed nucleus is present within the cell with nuclear membrane and nucleolus. Cell organelles like mitochondria, Golgi bodies, endoplasmic reticulum, etc. are also absent within their cell. Moreover their cell wall is composed of mucopeptide component. For this reason their nature is prokaryotic. Except blue green algae other algae are eukaryotic in nature.
What is periplast?
Ans. Besides cell-walled types, there are also some naked flagellated types of algae. In case of naked types, there is no cell wall but the protoplast is externally limited by a more or less rigid protoplasmic layer called periplast.
Write the names of the algal pigments, which are responsible for blue, brown and red colouration. (2)
Ans. Phycocyanin is responsible for blue colouration, phycoerythrin is responsible for red colouration and fucoxanthin is responsible for brown colouration.
What is pyrenoid?
Ans. Pyrenoids are protein bodies surrounded by loosely packed starch.
What is paradesmose?
Ans. The two blepharoplasts of Chlamydomonas are joined with each other by means of a fine fibril called paradesmose.
What are plakea and phialopore?
Ans. Each asexual reproductive cell gonidium of Volvox by repeated divisions produces spherical group of daughter cells, all of which are held together as a new daughter colony. The divisions occurring in the formation of a daughter colony are always longitudinal and all cells of the second cell generation divide at the same time. Four cells of the second cell generation are quadrately arranged, the 8 cells of the third cell generation are cruciately arranged, with a tendency to form a curved plate called plakea
Plakea takes the shape of hollow sphere at the end of the 16 celled stage. When a pore is formed at the anterior pole of the daughter colony of Volvox, it turns itself out by inverting through the phialopore.
What is stigma? What is its function? Where is it noted?
Ans. Stigma or eyespot is an orange-red coloured spot present at one side of the cup shaped chloroplast of Chlamydomonas. They are light sensitive and are supposed to help in directing the movement of the flagella present at the anterior end of Chlamydomonas.
Why is Chlamydomonas called “Green Yeast”?
Chlamydomonas is like yeast with chloroplasts:
a. It is unicellular.
b. It grows quickly.
c. It forms colonies on plates.
d. It has two mating types.
e. Chlamydomonas can grow as haploids or diploids.
f. It is easy to transform.
What is parthenospore?
Ans. Parthenogenesis may occur in Spirogyra sp. by the development of parthenospore or azygospore. These are formed when the gametes fail to fuse i.e. without fertilisation. During this process any one of the gametes secretes a thick wall around it to become a parthenospore, which after a period of rest germinates to form a new filament.
Name the reserve food matters of the following algae.
a. Brown algae
b. Golden brown algae (Diatom)
c. Red algae
b. Volutin, Leucosin
c. Floridian starch, Floridoside
If an alga is devoid of chlorophyll, would you call it a fungus?
Ans. No, the reasons are:
a. Algal body is composed of true parenchymatous tissue, but fungal body is composed of pseudoparenchymatous tissue.
b. Cell wall of algae is mainly composed of cellulose, but the fungus cell wall is made up of chitin mixed up with cellulose.
c. Reserve food matters of alga are mainly starch but in case of fungus reserve food matters is mainly glycogen.
d. Alga lives in water or in wet substratum but fungus lives as a parasite or a saprophyte in wet or dry places.
Write two Indian species of the following.
a) Chlamydomonas b) Volvox c) Spirogyra
a. Chlamydomonas eugametos and Chlamydomonas atactogama
b. Volvox minor and Volvox aureus
c. Spirogyra neglecta and Spirogyra elongata
What happens when Spirogyra is placed in 10% sugar solution?
Ans. If a Spirogyra filament is placed in a 10% sugar solution then plasmolysis will occur. As 10% sugar solution is a hypertonic solution. so water will come out of the cell due to exosmosis and shrinkage of protoplasm will occur.
What are axoneme and end piece?
Ans. The basal portion of each flagella of Chlamydomonas is covered by means of cytoplasm and is called axoneme. The naked part of the flagella, which remains beyond the cytoplasmic sheath, i.e. axoneme is called end piece.25. Describe the structure and function of neuromotor apparatus of Chlamydomonas. (2)
Ans. Paradesmose, rhizoplast together with the two blepharoplasts form the neuromotor apparatus.
Function: It controls the movement of flagella.
Name one parasitic algae
Name one Alga, which is used as commercial sources of Iodine.
If an algae is devoid of chlorophyll then it not be called as fungus due to following reasons.
- Algal body is parenchymatous tissue but Fungal body is pseudoparenchymatous.
- Cell wall of Algae is made up of cellulose but the Fungal cell is made up of chitin.
- Algal reserve food material is starch but Fungal reserve food material is glycogenIf you have enjoyed reading this post The Algae, I would be very grateful if you would help it to spread by sharing on social media like Facebook, Twitter, Google+, by clicking on the share buttons below. If you have any questions or comments, feel free to ask them in the comment section below.See you in my next blog post.PpGAlso Read on Science Reckoner: