Volvox - Diagram, Classification, Structure and Reproduction

Volvox: Volvox is a polyphyletic genus of chlorophyte green algae in the family Volvocaceae. These organisms usually form spherical colonies of up to 50,000 cells, which is why they are known as "globe algae." Volvox belongs to a larger group of multicellular species known as volvocine algae. They have different body sizes, cell counts, and degrees of cell-type specialisation.

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Volvox Diagram

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Volvox Classification

Volvox Characterstics

PROKARYOTIC CELLS

Volvox Structure

• Flagella: Each cell within a Volvox colony has two flagella, whip-like structures that protrude from the cell and are used for movement. The flagella beat coordinatedly, allowing the colony to move through the water.
• Nucleus: Volvox cells contain a nucleus, which houses the cell's genetic material and controls its activities.
• Chloroplasts: The cells of Volvox contain chloroplasts, which are responsible for photosynthesis. These chloroplasts are cup-shaped and contain pyrenoids, structures that help store starch.
• Eyespot: Some cells in Volvox colonies possess an eyespot, a light-sensitive organelle that helps the colony detect light direction.
• Contractile Vacuoles: Volvox cells also have contractile vacuoles, which regulate the cell's water content and maintain osmotic balance.

4. Cellular Connections: The cells within a Volvox colony are interconnected by cytoplasmic strands. These strands allow for cell communication, enabling them to coordinate their activities.

Sexual Reproduction in Flowering Plants

Volvox Unicellular or Multicellular

Volvox Locomotion

Connective Tissue

Volvox Reproduction

Asexual Reproduction in Volvox

1. Cell Growth and Development: Asexual reproduction begins with cells on the posterior side of the coenobium, the colony of Volvox, undergoing significant growth, increasing in size nearly tenfold.
2. Flagellar Withdrawal: As these cells grow, they withdraw their flagella, the whip-like appendages used for movement.
3. Inward Movement: The enlarged cells, now called parthenogonidia, are pushed inside the colony during their development, leading to their separation from other cells due to their size and position within the coenobium.
4. Cell Division: Each parthenogonidium undergoes multiple divisions, typically around 15, producing more than 3200 cells.

Female Gametophyte

Sexual Reproduction in Volvox

Vegetative Propagation

Life Cycle of Volvox

1.Sexual Reproduction Process:

• Oogonium Formation: All eggs are contained within specialized structures called oogonia, which also contain chloroplasts, giving them a greenish colour.
• Spermatozoon Production: Male gametes, or spermatozoa, are produced in antheridia. These spermatozoa are spindle-shaped and have a pair of apical cilia for movement.
• Fertilisation: Chemotactic movement attracts the spermatozoa to the oogonium, where a proteolytic enzyme breaks down the oogonium's wall, allowing the spermatozoon to enter. Only one spermatozoon is typically responsible for fertilising an egg.
• Zygote Formation: After fertilisation, a diploid zygote is formed, which turns red due to the presence of hematochrome, a red pigment.
• Cell Division: The zygote undergoes meiotic cell division to produce four haploid cells, which further divide through mitosis to form a new colony.

2. Asexual Reproduction Process:

• Gonad Production: Asexual reproduction involves the production of daughter cells, or gonads, through mitosis.
• Colony Formation: These daughter cells continue to divide, forming an invaginated colony within the parent colony.
• Release of Daughter Colonies: The daughter colonies eventually invert to form spheres and are released from the parent colony, completing the asexual reproduction process.