Volvox

Volvox refers to freshwater planktonic algae, which can float freely on the surface of the water. They exist in 20 unique genera, and are extremely beautiful to look at, often categorised as some of the most beautiful organisms in the plant kingdom. Understanding Volvox classification is essential if you hope to crack the NEET exams.

Read on to know more about Volvox algae, including its structure, characteristics and reproductive system. Notably, this is a vital topic in your NEET syllabus and you must be clear on its related concepts to attain a good rank in this examination.

Taxonomy of Volvox

To comprehend Volvox classification, refer to the following table. Keep in mind that Volvox’s Domain is Eukaryote. 

Volvox is a Chlorophyceae primarily because of the chlorophyll present inside it. 

Did You Know?

Father of microbiology, Antonie van Leeuwenhoek is credited as the first person to perform a detailed study on Volvox, thereby determining its characteristics.

Volvox Characteristics

To help you memorise and retain the characteristics of Volvox, the characteristics have been divided into pointers – 

• Spherical shaped individual cells.

• Each Volvox colony represents a ball-shaped structure with approximate diameters of around 0.5mm.

• To understand Volvox structure further, you should consider its plant body as a hollow sphere, referred to as the coenobium. Each of these coenobium houses thousands of cells.

• Glycoproteins make up the extracellular coenobium matrix.

• Pyrenoids are present inside chloroplasts.

• Chloroplasts are shaped like cups. 

• Flagellated somatic cells and germ cells are the two kinds of cells in coenobium.

• Each cell houses an eyespot, a nucleus and vacuoles.

• Adjacent cells are interconnected using cytoplasmic strands during cell division.

• All cells are capable of conducting metabolic activities independently, including photosynthesis, excretion, respiration, etc. 

• Volvox is responsible for the production of a significant amount of oxygen, allowing a wide range of aquatic organisms to utilise it.

• Two flagella in each cell assist in the movement of Volvox across the water body.

• When talking about Volvox characteristics, one cannot ignore the fact that eyespots in each cell act as light receptors, helping in phototaxis mobility.

• In some cases, Volvox can reproduce rapidly, leading to harmful algal bloom or HAB, which is responsible for increased nitrogen concentration in warm water bodies.

Illustration of Volvox

If it is too difficult to picture a Volvox from the characteristics listed above. Consequently, refer to this Volvox diagram below.

In the diagram, you can see individual cell structure, along with its contents. Furthermore, you can also get an idea regarding the functionality of Volvox.

Volvox Reproduction   

Volvox can reproduce both sexually and asexually. The former is reserved only for unfavourable conditions. For instance, sexual reproduction in Volvox is more common when the summer months draw toward an end. 

• Asexual Reproduction – 

Cells on the posterior side of the coenobium grow to almost 10 times their normal size. These cells withdraw their flagella, and they are pushed inside the colony during their development. 

Such cells, known as parthenogonidia, are separated from the other cells due to their size and position. Each parthenogonidia divide at least 15 times, developing more than 3200 cells.

• Sexual Reproduction – 

As stated above, sexual reproduction occurs under unfavourable conditions only. However, such a form of reproduction in Volvox is always oogamous. Depending on the exact species, though, this can either be dioecious and monoecious.

Volvox Life Cycle

Now that you possess a brief idea regarding the reproductive system in Volvox, here are some pointers about its life cycle.

• Sexual reproduction involves male cells (spermatozoa) and female cells (ova).

• All ova exist inside oogonium, and they include chloroplasts, which give them a greenish tinge.

• Antheridium produces spermatozoa, which are spindle-shaped and come with a pair of apical cilia. 

• Chemotactic movement is responsible for attracting antherozoids to the oogonium. Once the former reaches the oogonium, a proteolytic enzyme breaks down its wall, allowing the antherozoid to enter.

• Multiple sperms enter the oogonium, but only one antherozoid is responsible for the fertilisation.

• After fertilisation, a diploid zygote is formed. After formation, such zygotes turn red primarily due to the presence of hematochrome. 

• Through meiotic cell division, each zygote forms four haploid cells. 

• Furthermore, several mitotic divisions take place, leading to the formation of a colony. This, in turn, continues the Volvox life cycle.

In asexual reproduction, mitosis causes the production of daughter cells. Each daughter cell is known as a gonad. The same process continues until an invaginated colony of daughter cells is formed. These daughter cells are inverted to form spheres, much before being actually released from the parent colony. 

Prepare Well for Your NEET and Ace This Exam!

Now that you know more about Volvox classification make sure you devote enough time to the other topics in Biology. This subject can help you fetch great marks in your class XII examinations as well as in NEET.

Furthermore, while learning about the life cycle of Volvox and other topics, do not forget about your personal health. Ensure you take proper care of your diet and sleep for at least 7 hours each day. Failing to adhere to these tips can severely restrict your exam preparations, limiting your ability to concentrate.