Problem 2 - Campbell Biology

Question

. Which phylum is characterized by animals that have a segmented body? \begin{equation}\begin{array}{ll}{\text { (A) Cnidaria }} & {\text { (C) Arthropoda }} \\ {\text { (B) Platyhelminthes }} & {\text { (D) Mollusca }}\end{array}\end{equation}

Step-by-Step Solution

Answer

Arthropoda

Step 1: Understand the Question

Identify the phylum that is known for having animals with a segmented body from the given options (A, B, C, D).

Step 2: Recall Characteristics of Each Phylum

Review the main features of each phylum: (A) Cnidaria - Known for having a simple body plan with radial symmetry and no segmentation.(B) Platyhelminthes - Known for having a flattened body, also without segmentation.(C) Arthropoda - Known for having a body divided into segments with a hard exoskeleton.(D) Mollusca - Known for having a soft body, usually protected by a hard shell, but typically not segmented.

Step 3: Identify the Correct Phylum

Based on the characteristics of each phylum, determine which one has segmented bodies. The correct phylum is Arthropoda.

Step 4: Confirm the Answer

Verify that Arthropoda is indeed the phylum known for segmented bodies, which includes insects, arachnids, and crustaceans.

Key Concepts

phylum Arthropoda

The phylum Arthropoda is a major group in the animal kingdom that includes animals like insects, arachnids, and crustaceans. These creatures are characterized by their segmented bodies and exoskeletons, which provide support and protection. The word 'arthropoda' itself comes from the Greek words 'arthro,' meaning joint, and 'podos,' meaning foot, referring to their jointed limbs. Segmentation refers to the division of their bodies into different sections or segments, which enables them to move efficiently.
Arthropods are incredibly diverse, making up more than 80% of all known animal species. They can be found in nearly every habitat on Earth, from deep oceans to high mountains. The segments in their bodies often have specialized functions, like sensory detection, locomotion, or feeding, making them incredibly versatile and adaptable to different environments.

characteristics of Arthropoda

Arthropods exhibit several key characteristics that set them apart from other animal phyla. Some of the most important ones include:

• Segmented bodies: Their bodies are divided into segments, typically divided into the head, thorax, and abdomen.
• Exoskeleton: They possess a hard exoskeleton made of chitin, which provides structural support and protection. To grow, arthropods must molt, shedding their old exoskeleton and forming a new, larger one.
• Jointed appendages: Their limbs are jointed, allowing for a wide range of movements. This adaptability is crucial for tasks like walking, swimming, or catching prey.
• Complex life cycles: Many arthropods undergo metamorphosis, a process where they develop through distinct stages – like egg, larva, pupa, and adult – each with unique forms and functions.

These characteristics make arthropods some of the most resilient and adaptable animals on Earth.

animal segmentation

Segmentation in animals is the division of an animal's body into repetitive segments. This feature is not unique to arthropods; it also appears in other phyla such as Annelida (segmented worms) and Chordata (vertebrates). However, the way segmentation is manifested in arthropods is quite distinct.
In arthropods, segmentation allows each body segment to specialize and perform specific functions, contributing to the overall efficiency and adaptability of the animal. The head typically houses sensory organs and mouthparts, the thorax includes structures for locomotion like legs and wings, and the abdomen contains organs related to digestion and reproduction.
This modular design helps arthropods survive in various environments because they can easily adapt to different functional needs. For instance, some legs might evolve into pincers for grasping, while others could develop into specialized structures for swimming. The segmented body plan thus provides a flexible template for evolutionary changes, allowing these animals to diversify and thrive in a multitude of niches.