Problem 11 - Biology

Question

Collar cells (choanocytes) are characteristic of phylum (a) Porifera (b) Cnidaria (c) Coelomata (d) Lophotrochozoa (e) Ecdysozoa

Step-by-Step Solution

Answer

Choanocytes are characteristic of phylum Porifera (a).

Step 1: Understanding Choanocytes

Choanocytes, also known as collar cells, are specialized cells used in the process of filtering and obtaining food in certain organisms. These cells have a distinctive structure with a flagellum surrounded by a collar of microvilli which creates water currents to trap food particles.

Step 2: Identifying the Phylum

Choanocytes are characteristic of the phylum Porifera. Organisms in this phylum are commonly referred to as sponges. Sponges are simple, multicellular organisms that primarily inhabit marine environments and rely on choanocytes for feeding.

Key Concepts

Choanocytes

Choanocytes play a crucial role in the survival of sponges, acting as their primary feeding mechanism. These specialized cells are equipped with a flagellum, a whip-like structure that beats to create water currents. Surrounding the base of the flagellum is a collar composed of microvilli.

• The movement of the flagellum draws water through the sponge's porous body, enabling the organism to filter out food particles.
• The microvilli trap these particles, usually composed of bacteria and plankton, which are then engulfed by the cell.

This feeding process is known as filter feeding. Additionally, choanocytes aid in the sponge's reproductive processes by capturing sperm from the water, facilitating fertilization.

Collar Cells

Collar cells, another name for choanocytes, are pivotal to understanding the biology of sponges. They not only help in feeding but also play a part in the respiration and filtering systems of these simple creatures.

• The structure of collar cells is highly efficient at moving large volumes of water through the sponge’s body.
• This efficiency ensures the sponge can both gather enough nutrients and remove waste materials.

Through this movement, the cells also facilitate oxygen diffusion directly into the sponge's internal tissues, while helping to expel carbon dioxide and other waste products with the outgoing water.

Sponges

Sponges, or Porifera, are fascinating organisms known for their simplicity and ecological importance. Although they lack true tissues and organs, sponges are highly adapted to their environments.

• They reproduce both sexually and asexually, with some species having remarkable regenerative capabilities.
• Most sponges live in marine environments, although a few inhabit freshwater.

In the ecosystem, sponges provide habitats for numerous marine organisms. Their filter-feeding habits help maintain water quality by trapping and breaking down particulate matter from the water.

Marine Biology

Marine biology explores the diverse forms of life in the ocean, with sponges being one of the earliest multicellular organisms in marine ecosystems. Understanding sponges and their interactions within marine environments is key to comprehending broader ecological dynamics.

• Sponges serve as important indicators of ocean health due to their sensitivity to water conditions.
• Studies on sponges have contributed to discoveries in bioactive compounds, beneficial in medical research and pharmacology.

Marine biologists continue to explore how these ancient organisms will adapt to modern challenges, such as climate change and pollution, which impact marine ecosystems globally.