Problem 13 - Biology Today and Tomorrow Without Physiology

Question

Silica-rich remains of __________ are used as an insecticide. a. dinoflagellates b. diatoms c. foraminiferans d. apicomplexans

Step-by-Step Solution

Answer

Diatoms (option b) have silica-rich remains used as an insecticide.

Step 1: Understanding the Question

The question asks us to identify which group of organisms has silica-rich remains that are used as an insecticide. This means looking for an organism known for having a silica component in its structure.

Step 2: Analyzing the Options

Examine each of the given options: - **Dinoflagellates:** These are a group of single-celled organisms, but they have cellulose plates rather than silica in their cell structure. - **Diatoms:** These are a group of algae known for their silica cell walls, often referred to as frustules. - **Foraminiferans:** These are amoeboid protists with calcareous shells, not silica-rich. - **Apicomplexans:** These are parasitic organisms lacking silica-based structures.

Step 3: Identifying the Correct Organism

Based on the analysis, **diatoms** are known for their silica cell walls. Their remains, often termed "diatomaceous earth," are indeed used as an insecticide due to their abrasive properties. This matches our requirement for silica-rich remains.

Step 4: Selecting the Correct Answer

Having identified diatoms as the organisms with silica-rich remains, we determine that the correct answer to the exercise is option (b) diatoms.

Key Concepts

Silica-rich remains

When these organisms die, the silica structure does not decompose easily. They leave behind a significant amount of silica-rich material. This process contributes to the formation of what's called *diatomaceous earth*. These remains accumulate over millions of years, forming thick layers at the bottom of bodies of water. Silica is a natural compound made of silicon and oxygen. Diatoms use silica to create their cell walls, which provide both protection and rigidity. This is why, even after diatoms perish, their silica shells remain intact, continuing to have practical uses long after their lifecycle.

• Diatoms are one of Earth's most important producers of oxygen.
• Silica-rich remains help in maintaining the health of aquatic ecosystems.

Insecticide

Diatomaceous earth is an effective natural insecticide due to its physical properties. The tiny shards of silica are sharp to insects but harmless to humans and pets. Once diatomaceous earth comes into contact with insects, it cuts through their exoskeletons. This physical abrasion causes insects to dehydrate and eventually leads to their death. Diatomaceous earth's use as an insecticide is considered sustainable and environmentally friendly. It avoids the chemical residues associated with synthetic pesticides, making it a preferred option for organic farming.

• Safe for use around the home and garden.
• No harmful chemicals involved, making it eco-friendly.
• Can control a wide range of insects including ants, cockroaches, and fleas.

Diatomaceous earth

Diatomaceous earth is mined from deposits formed by the fossilized remains of diatoms. It appears as a fine, white, powdery substance and is comprised largely of silica. This material has various uses beyond insect control. It is often used in filtration processes for swimming pools and even in food and beverage industries as a filtering aid. Due to its mild abrasive properties, it is also utilized in products like toothpaste and polishes.

Multiple Applications of Diatomaceous Earth

Diatomaceous earth is a versatile substance used in several domains:

• As a gentle abrasive in cleaners and personal care products.
• As an anti-caking agent and soil conditioner in agriculture.

With its multitude of applications, diatomaceous earth proves to be a fascinating and essential resource derived from one of nature's simplest organisms.