[Biology Class Notes] on Chlamydomonas Pdf

Microorganisms are something that goes beyond the human eyes and these need special instruments through which they can be perceived. One of these microorganisms that needs an instrument to be seen through is Chlamydomonas. Chlamydomonas is a genus that consists of at least 325 species of unicellular green algae. These are found commonly in seawater, stagnant water, freshwater, and even in moist soil. To learn more about the Chlamydomonas – Meaning, Structure, Life Cycle, Function, and FAQs students can refer to and check out all about the topic.

Chlamydomonas is a genus of green algae with about 325 members that are all unicellular flagellates found in stagnant water, moist soil, freshwater, seawater, and even snow as “snow algae.” Chlamydomonas is a model organism for molecular biology research, especially for the studies of flagellar motility, chloroplast dynamics, biogenesis, and genetics. Chlamydomonas have ion channels (channelrhodopsins) that are directly activated by light, which is one of its many distinguishing characteristics. 

Chlamydomonas regulatory systems are more complex than Gymnosperm homologs, with evolutionarily related regulatory proteins being larger and possessing more domains. Chlamydomonas plant-animal that is still related to the two kingdoms’ last shared ancestor. For decades, green yeast has been a resident of the laboratory. It has a fascinating morphology and behavior and is easy to develop in liquid cultures.

 

Structure of Chlamydomonas

Chlamydomonas algae is a green alga that is unicellular and motile. Chlamydomonas structure is a single cell used to represent the thallus. It measures approximately 20 p,-30|i in length and 20 p,-30|i in diameter. Thallus may be circular, rectangular, oblong, ellipsoidal, or pyriform in shape. The pyriform or pear-shaped thalli, which have a narrow anterior end and a wide posterior end, are normal. Their shape is oval, spherical, or pyriform. The cell is surrounded by a cellulose cell wall that is thin and firm. Between the cell membrane and the chloroplast is the cytoplasm. The cell has a huge dark nucleus that is located within the cup-shaped chloroplast cavity. Two flagella are found in the cell’s anterior region, which aids in locomotion. Every flagellum has two contractile vacuoles at the base. A small red eyespot can be found on the chloroplast’s anterior side. Given below is the Chlamydomonas structure with labels. 

 

The Life Cycle of Chlamydomonas 

Chlamydomonas Reproduction is both sexual as well as asexual reproduction.

Asexual reproduction takes place by following methods:

1. Zoospore Formation: The protoplast separates from the cell wall as it contracts. The parent cell loses its flagella, or in certain Chlamydomonas species, the flagella are absorbed. The neuro-motor apparatus and contractile vacuoles vanish. Simple mitotic division divides the protoplasm longitudinally, resulting in two daughter protoplasts. The protoplasm’s second longitudinal division occurs at a right angle to the first, resulting in four daughter chloroplasts. The protoplasm will often divide again, resulting in 8-16-32 daughter protoplasts. 

 

Pyrenoids and neuro-motor apparatus initials also divide. Daughter protoplasts also form contractile vacuoles. Each daughter cell develops its cell wall, flagella, and zoospore. Gelatinization or rupture of the cell wall liberates the zoospores from the parent cell or zoosporangium. The zoospores have the same structure as the parent cell but are smaller. To mature Chlamydomonas, the zoospores enlarge. The formation of zoospores will occur every 25 hours under ideal conditions.

 

2. Aplanospores Formation: Flagella are lost by the parent cell. The protoplast is rounded on the outside and secretes a thin wall, but it lacks pore flagella. Aplanospores are these non-motile structures. Aplanospores can germinate directly or divide to produce zoospores as favorable conditions approach.

 

3. Hypnospores Formation: In severe unfavorable conditions, the protoplast forms a thick wall, which is known as Hypnos pore. On the approach of favorable conditions, hypnospores germinate similarly to aplanospores.

 

4. Palmella stage: Under unfavorable circumstances, such as a lack of water or an abundance of salts, the palmella stage develops. The parent cell’s protoplast divides into several daughter protoplasts, but none of them forms zoospores. A mucilaginous sheath forms around daughter protoplasts as the parent cell wall gelatinizes. The daughter protoplasts form a gelatinous wall around themselves as well, but they lack flagella. Palmellospores are the protoplast segments that make up the palm. The division and red visions of these protoplasts eventually result in the formation of an amorphous colony with an infinite number of spores, which is known as the palmella stage. The gelatinous wall is removed, palmettosports produce flagella, and the spores are released to form new thalli when favorable conditions return.

 

Sexual Reproduction: Sexual reproduction in Chlamydomonas may be isogamous, anisogamous, or oogamous. The thallus can be homothallic or heterothallic, The gametes can be naked (gymnogametes) or protected by the cell wall.

• Anisogamy: The fusing pairs, in this case, are identical in form but different in scale. Four larger macrogametes are produced by the female cell. Eight smaller microgametes are produced by the male cell.

• Oogamy: The vegetative thallus, which is acting as a female cell, removes its flagella and acts as a non-motile macrogamete or egg. Pyrenoids are abundant in the female gamete. 

 

Chlamydomonas Classification

The Chlamydomonas is classified under these categories.

 

Chlamydomonas Characteristics

The unicellular, pear-shaped, and biflagellate plant body is unicellular, pear-shaped, and biflagellate. Each cell has two contractile vacuoles, one eye-spot, and a cup-shaped chloroplast. Palmella-stage is present. Biflagellate zoospore formation is used for asexual reproduction. Iso-, aniso- and oogamy are all forms of sexual reproduction.

 

Chlamydomonas Function

Chlamydomonas is a model organism for research into flagellar motility, chloroplast dynamics, biogenesis, and genetics. Chlamydomonas have ion channels (channelrhodopsins) that are directly activated by light, which is one of its many distinguishing features.