Problem 13 - Biology Today and Tomorrow with Physiology

Question

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

Step-by-Step Solution

Answer

The silica-rich remains of diatoms are used as an insecticide.

Step 1: Understand the Question

The question asks about organisms whose silica-rich remains are used as an insecticide. We need to identify which organism's remnants have this property from the given options: dinoflagellates, diatoms, foraminiferans, or apicomplexans.

Step 2: Define the Options

Let's understand each option briefly: - Dinoflagellates: A type of algae, some are bioluminescent and not typically known for silica-rich remains. - Diatoms: Microscopic algae with silica cell walls, known for their silica-rich exoskeletons called frustules. - Foraminiferans: Marine organisms with calcareous shells, not silica-based. - Apicomplexans: Parasitic protozoans, not known for forming silica structures.

Step 3: Identify the Correct Organism

From the definitions, diatoms are the only group known for having silica cell walls. Therefore, their remains, which are silica-rich, are used as an insecticide, commonly known as diatomaceous earth.

Step 4: Conclusion

Based on the information analyzed, the silica-rich remains of diatoms are used as an insecticide. This aligns perfectly with the use of diatomaceous earth, made from diatom remnants.

Key Concepts

Silica-rich remains

Diatoms are fascinating microscopic algae that are an essential part of aquatic ecosystems. One of their most notable features is their silica-rich cell walls. These walls, known as frustules, are made of silica—a hard, glass-like material. When diatoms die, these silica-rich remains settle to the bottom of water bodies and form deposits. Over time, these deposits accumulate, creating a substance that is rich in silica. This process results in the formation of diatomaceous earth.

Diatomaceous earth is essentially a fine, powdery substance formed from the collected remains of ancient diatoms. These remains are packed with silica and, as such, have important industrial applications. The high silica content makes the material abrasive and useful in various products, including as a natural insecticide. The abrasive nature of diatomaceous earth allows it to damage the exoskeletons of insects, leading to their dehydration and eventual demise.

Insecticide

Diatomaceous earth serves as a natural insecticide and is appreciated for its safety compared to chemical alternatives. When used as an insecticide, its primary mechanism of action is physical rather than chemical. Here's how it works:

• The fine particles of diatomaceous earth attach to the outer shell or exoskeleton of insects when they come into contact.
• The abrasive quality of the particles causes small cuts or abrasions on the exoskeleton.
• These abrasions then lead to dehydration, as the damage causes insects to lose moisture rapidly.

Because its action is primarily physical, diatomaceous earth is considered non-toxic to humans and pets, making it a popular choice for home use against pests such as ants, bed bugs, and cockroaches. It does require reapplication—particularly if washed away by rain—but remains a highly effective natural solution. Remember, though, that despite its safety, inhaling large amounts of the fine powder should be avoided.

Diatomaceous earth

Diatomaceous earth is a naturally occurring, soft, and powdery sedimentary rock that is comprised primarily of the fossilized remains of diatoms. These remains are primarily made up of silica, giving the material its name. Various types of diatomaceous earth exist, and it is classified based on its different applications, such as:

• Filter Grade: Used industrially to purify liquids, such as in the production of beer, wine, and juices.
• Food Grade: Safe for consumption, frequently used as a health supplement due to its mineral content.
• Pesticide Grade: Used effectively for pest control, relying on its insecticidal properties.

Diatomaceous earth is not just limited to pest control. It has a wide range of applications, including as an abrasive in toothpastes and polishes, as a stabilizing component in dynamite, and even as an additive in animal feed to aid digestion. Its versatility, abundance, and safety make it highly valuable across a diverse range of industries. Whether you're looking at improving filtration processes or naturally dealing with pests, diatomaceous earth offers a reliable and sustainable solution.