Problem 6 - Biology Today and Tomorrow with Physiology

Question

The ______ have a cuticle and molt as they grow. a. roundworms b. annelids c. arthropods d. both a and c

Step-by-Step Solution

Answer

Both roundworms and arthropods molt; option d is correct.

Step 1: Understanding the Question

The question is asking which organisms have a cuticle and undergo molting as they grow. We need to identify the types of organisms that exhibit these characteristics.

Step 2: Identifying Characteristics of Each Group

a. Roundworms (Nematodes) - These organisms have a cuticle and molt as they grow. b. Annelids - These are segmented worms like earthworms that do not have a cuticle for molting. c. Arthropods - This group includes insects, arachnids, and crustaceans, all of which have a cuticle and molt as they grow.

Step 3: Analyzing the Options

Option a mentions roundworms, which molt. Option b mentions annelids, which don't molt. Option c mentions arthropods, which molt. Option d suggests both a (roundworms) and c (arthropods), both of which have a cuticle and molt.

Step 4: Selecting the Correct Answer

From the analysis, both roundworms and arthropods have a cuticle and molt as they grow. Therefore, the correct answer is option d, 'both a and c'.

Key Concepts

Roundworms

Roundworms, scientifically known as nematodes, are simple but fascinating creatures. They are one of the most abundant groups of animals on Earth. Roundworms have a cylindrical body that is often pointed at both ends.
Their body is covered with a flexible, yet tough layer known as a cuticle. This cuticle is essential for their growth and survival.
A remarkable feature of roundworms is their process of growth, known as molting. As roundworms grow, they shed their cuticle to make space for a new, larger one. This molting process is crucial as it facilitates their growth and adaptation to the environment.
Key characteristics of roundworms include:

• They are cylindrical and often very tiny.
• A flexible cuticle covers their bodies.
• They undergo molting to grow.

Roundworms are immensely diverse and can be found in virtually any habitat, from deep oceans to the soil in your backyard.

Arthropods

Arthropods are the largest group of animals on Earth, including insects, spiders, and crabs. These creatures have segmented bodies, jointed limbs, and a hard exoskeleton made of chitin. This exoskeleton protects their bodies and provides attachment points for muscles, allowing them to move efficiently.
Like roundworms, arthropods undergo molting to grow. Since their exoskeleton doesn't expand, they periodically shed this outer layer in a process similar to changing a suit of armor. This molting allows them to increase in size and develop further.
Arthropods exhibit several fascinating attributes:

• They have jointed limbs for versatile movement.
• An exoskeleton made of chitin gives them protection and mobility.
• They grow through a process of molting, where they shed their old exoskeleton.
• This group includes a diverse range of animals such as insects, arachnids, and crustaceans.

Due to their adaptability and diverse range of forms, arthropods inhabit every ecosystem on Earth, from deserts to rainforests.

Molting

Molting is a fundamental biological process vital for the growth and development of certain animals, including roundworms and arthropods. This process involves shedding or casting off an outer layer, such as a cuticle or exoskeleton, and growing a new one in its place.
The molting cycle generally includes several stages:

• The old layer is loosened, often with the help of special enzymes.
• The animal creates a new layer underneath the old one.
• Finally, they shed the old layer, allowing the new, slightly larger structure to expand.

Molting provides several advantages:

• It allows the organism to grow larger, replacing their restrictive outer layer.
• New outer layers can help them adapt better to environmental changes.
• This process can also contribute to the repair or renewal of damaged body parts.

This incredible adaptation has allowed species like roundworms and arthropods to thrive in a multitude of environments, supporting their evolution and survival through changing conditions of the environment.