Test: Algae - 1

• Plants that do not have well-differentiated body design fall in this group. They are commonly called algae.
• Algae are chlorophyll-bearing, simple, thalloid, autotrophic and largely aquatic (both fresh water and marine) organisms.
• Thallus: A plant body not differentiated into stem, leaves, and roots and without a vascular system, typical of algae, fungi, lichens, and some liverworts.

• Cephaleuros virescens (green alga) is parasitic on leaves of tea, coffee and mango which causes red rust of tea, coffee.
• Harveyella is parasitic red alga which lives as parasite on other photosynthetic red algae.

• R-Phycoerythrin is a protein that belongs to the phycobiliprotein family and acts as an accessory pigment for photosynthesis in Rhodophyta.
• The red pigment R-phycoerythrin can absorb the blue-green spectrum of light from the deep seas along with chlorophyll-a for photosynthesis.
• In deep waters, more phycoerythrin is formed as compared to chlorophyll making the red algae look more red.

Rhodophycophyta reproduce sexually heterogamously by the union of well-differentiated nonmotile male and female germ cells, the spermatia and carpogonia (female sex organs), respectively.

Protonema represents the juvenile stage of moss (funaria). It is much-branched, green filamentous structure formed by the germination of spores, under favourable conditions.
The protonema consists of:
(a) some slender rhizoids.
(b) a number of aerial green prostrate branches bearing small lateral buds which grow up into new moss gametophores.

Red rust disease of tea is caused by an alga Cephaleuros parasiticus Karst. The genus Cephaleuros is a parasitic green alga belonging to the family Trentepoholiaceae of the Division Chlorophyta in the algal kingdom.

Kelps belong to brown algae which carry almost the same pigments as in diatoms. one of them is fucoxanthin.

• Brown algae (Phaeophyceae) are characterized by the presence of motile reproductive phase (zoospores) with two lateral flagella.
• Green algae (Chlorophyceae) reproduce by zoospores with two identical anterior flagella.
• Xanthophyceae is characterized by the formation of zoospores with paired flagella with unequal length.
• Cyanophycean reproduce by simple division/fragmentation or nonmotile spores and do not exhibit any motile phase during the life cycle.

Thallophyta is that phylum of plant in which the thallus(body) is not differentiated into leaves, or stem, etc. They do not have a vascular bundles also.

Sargassum is a kind of brown algae which is a free floating algae. It has also got a name Gulf weed due to this property. It grows rapidly in North Atlantic ocean and covers thousands hectares of area, therefore this region is called as Sargasso Sea.

Zygotic meiosis is a characteristic feature of Algae or Thallophytes.
So here are a few points about Zygotic meiosis:

1. This process takes place in the Zygote.
2. Haploid organism is formed by this process.
3. This cycle is Haplontic.

• Chlorophyll a acts as a reaction center and carotene shows a wide range of light absorption for photosynthesis.
• In all algae, chlorophyll-a acts as a reaction center which absorbs light energy and converts it into chemical energy which makes photosynthesis possible.
• Carotene and chlorophyll-a molecules are water insoluble and remains attach to the cell.
• Carotene absorbs light energy and transfer it to chlorophyll a as they cannot directly transfer it to photosynthetic pathway.
• Carotene are orange yellow red color pigments which shows a wide range of light absorption in photosynthesis.

Other options: 

•  Chlorophyll b occurs only in green algae and plants.
• Xanthophyll occurs only in Phaeophyta (brown algae) and Chlorophyta (green algae). 

Cyanobacteria are classified under Kingdom Monera.
(i) Protista— unicellular eukaryotes
(ii) Plantae, all members of Kingdom Plantae are eukaryotic chloroplast chlorophyll containing organisms commonly called plants. These are autotrophic/holophytic.

• Red algae is sitted in benthic zone of sea.
• For photosynthesis they need blue light instead of red light and deep in the sea blue light is able to reach there and red light is absorbed only till a few meters in water.

The two classes of phycobilins include phycocyanin and phycoerythrin. Phycocyanin is a bluish pigment found in primarily cyanobacteria (blue-green algae) to aid in absorption of light in photosynthesis, while phycoerythrin is a pigment found in Rhodopyta (red algae) that is responsible for its characteristic red color.

Both groups have Chlorophyll 'a' and similar accessory pigments such as β- carotenes, and phycobiliproteins. Both groups show thylakoids which occur singly as opposed to the stacked arrangement seen in other algal groups. Major food reserve of Cyanobacteria and Rhodophycean starch are quite similar to each other. Both groups have no flagellate forms.

• The vegetative cell has a cellulosic wall usually covered on the outside by a gelatinous coating of algin. On the cell wall of brown algae, some colloid substances like fucinic acid, alginic acid and fucoidan are present which are known as hydrocolloids.
• The cell wall of red algae is complex and made up of cellulose & pectin. The cell wall of red algae is also complicated like blue-green algae. Their cell wall has many different types of substances such as xylan, galactose, polyuronic acid, polysulfate esters.
• In dinoflagellates, cell wall has a stiff cellulose plate on the outer surface.
• In diatoms, the cell wall is made up of silica (hydrated silicon dioxide) called as frustule. They are the major group of algae, most common Chrysophytes.

Stonewort the common name for the brittle, calcified plants of the Charophyta; Chara and Nitella are the commonest British genera. The plant consists of a ‘stem’ or axis which bears whorls of branches at intervals (nodes) along its length. The axis is attached at its base to the substratum by means of branched rhizoids.

Irish moss is a member of the red algae group.

It grows in cold water and is used in raw food recipes for nutrition and thickening properties. Irish Moss has been used for centuries in Ireland, thought it also grows in Asia and the oceans of North America. Raw foodists love Irish Moss for its use as a thickener, so it is a great addition to a raw vegan diet.

• Cytological structure of all the above options revealed that they lack flagella. 
• Red alga is eukaryotic without flagella, centrioles, with phycobiliproteins and chloroplast lacking external endoplasmic reticulum and unstacked thyllakoid. 
• Cyanobacteria do not have organs for movement such as flagella, but some filamentous BGA exhibit gliding movement due to slime secretion along with contractile waves in the cells.
• In case of higher seed plants (Spermatophyta) like gymnosperm and angiosperm, flagella are absent since, presence of pollen grain eliminated use of water for fertilization. 

• Red algae are also known as rhodophytes, which is are eukaryotic alga without flagellate of which around 7000 living species are known till now. Red algae are marine species.
• Since they doesn't have flagella so motile stage is absent.
• It varies from unicellular to complex-multicellular algae.
• Most of them are autotropic except Harveyella which is a colorless parasitic red alga. 
• Harveyella cells show secondary pit connections with other parasitic cells or host.
• Mostly Harveyella is parasitic over Polysiphonia.

The correct answer is 'D' because the green algae consist of green pigment for photosynthesis, cell wall to protect from outer environment as it is present on the root nodes and, store water and then supplies to the plant.

Pyrenoids consist of dense proteinaceous area surrounded by starchy sheath. These are unique to chloroplast of algae and are associated in polymerising sugars into reserve polymers (starch).

• Chlorophyta reproduce both sexually and asexually, but usually sexually.
• Asexual reproduction can occurs by fission, fragmentation, or zoospores.
• Sexual reproduction can be isogamous, anisogamous, or oogamous.
• In the haploid phase, gametes are formed; in the diploid phase, zoospores are formed.

The term Thallophyta was coined by Endlicher. The organisms included in Thallophyta are algae, fungi, slime mould and bacteria. 

F.E. Fritsch (1935) divided algae into following eleven classes in his book "Structure and Reproduction of the Algae", mainly on the basis of pigmentation, reserve food and flagellation, thallus structure, modes of reproduction and life cycles and he is known as father of algae.

In thallophytes, plant body is simplest of all and is not differentiated into root, stem and leaf. Such a body is called as a thallus. Reproductive parts are unicellular and the main plant body is gametophyte.

Characteristics of Thallophyta :

• Do not have well differentiated body .
• They are having thalloids i.e. root and stem .
• Vascular system is absent i.e. conducting tissues are absent.
• They are aquatic plants.
• Spores are present.
• The sex organs are unicellular and when multicellular, all are fertile.
• Example - Ulva , Chara , Spirogyra etc.

• Thallophyta reproduce sexually when gametes fuse to form a zygote. 
• There are three types of sexual reproduction on the morphological and physiological behavior gametes.
• Isogamous: both the gametes are morphologically and physiologically similar and their fusion is called as isogamy. 
• Anisogamous: The microgamete is smaller and more active, whereas the female gamete is larger and sluggish and their fusion is called as anisogamy. 
• Oogamous: female gamete is large and nonmotile and male gamete is small and motile and their fusion is called as oogamy.

Thus, the correct and answer is option D.

• Chlorophyceae (belongs to Chlorophyta) stands nearer the main lines of evolution towards land plants than any other algal class because of the presence of photosynthetic pigments chlorophyll a and b, starch as reserve product and cellulosic cell walls.
• Chlorophyta or Prasinophyta is a taxon of green algae informally called chlorophytes.
• The name is used in two very different senses, so care is needed to determine the use by a particular author.