Problem 116 - Objective Biology for NEET

Question

Which of the following belongs to arthropods? (a) Peripatus and crab (b) Prawn and scorpion (c) Centipede and cockroach (d) All of these

Step-by-Step Solution

Answer

The correct answer is option (b) and option (c). Both prawns and scorpions, and centipedes and cockroaches belong to the arthropod phylum.

Step 1: Understand Arthropods

Arthropods are invertebrates with segmented bodies, jointed limbs and exoskeleton mainly composed of chitin. Examples include crabs, scorpions, spiders, centipedes and insects such as a cockroach.

Step 2: Analyze Option (a)

Peripatus is an onychophoran, not an arthropod, whereas a crab is an arthropod, belonging to the crustacean group.

Step 3: Analyze Option (b)

Prawns and scorpions both are arthropods, prawn is an example of a crustacean, scorpions belong to the arachnid group.

Step 4: Analyze Option (c)

The centipede from the myriapods group, and a cockroach which is an insect, are both arthropods.

Step 5: Analyze Option (d)

As analyzed, options (b), and (c) fully consist of arthropods, but option (a) partly includes a non-arthropod creature. Therefore, option (d) is not correct.

Key Concepts

Invertebrates

Invertebrates are animals that lack a backbone or vertebral column. They make up the majority of animal species on Earth, exploring diverse adaptations to survive in varied environments. One of the most diverse groups within invertebrates is the arthropods.
Arthropods include species like insects, arachnids, and crustaceans, all characterized by their exoskeletons and jointed limbs. The absence of a spine in invertebrates allows for a great variety of body structures and functions. This flexibility enables them to inhabit every conceivable habitat on the planet from the ocean depths to the highest trees.

• Arthropods possess exoskeletons, which are external skeletons providing support and protection.
• Invertebrates can be aquatic or terrestrial, demonstrating vast ecological breadth.
• They reproduce in various ways, from laying eggs to live birth, adapting to their specific environments.

Learning about invertebrates opens a window into the incredible diversity that underpins much of life's complexity on Earth.

Arachnids

Arachnids are a fascinating group within arthropods known for their eight-legged feature. This group includes spiders, scorpions, ticks, and mites. Unlike insects that have three body segments, arachnids typically have two segments: the cephalothorax and the abdomen.
Arachnids exhibit various adaptations suited for life as predators or parasites. Many have specialized appendages near their mouths called chelicerae, which they use to grasp or immobilize prey.

• Most arachnids are terrestrial, although some, like sea spiders, inhabit marine environments.
• They lack antennae, a distinguishing characteristic compared to insects.
• Their respiratory systems can include book lungs or tracheae, depending on the species' evolutionary path.

Studying arachnids showcases the specialized niches arthropods can occupy, exploiting their environments with efficient adaptations.

Crustaceans

Crustaceans are primarily aquatic arthropods, famous for their hard exoskeletons and a wide range of body forms. This group includes crabs, lobsters, shrimps, prawns, and barnacles. Crustaceans usually have a body divided into three parts: the cephalothorax, abdomen, and carapace which is a shell covering part of the body.
These adaptations allow crustaceans to thrive in the diverse and competitive aquatic habitats. The life cycles of many crustaceans involve complex stages featuring transformations from larvae to adults.

• Nearly all crustaceans have gills for breathing, allowing them to extract oxygen from water.
• They play essential roles in aquatic ecosystems, acting as scavengers that recycle nutrients.
• Crustaceans are often vital food sources for humans and many other animals.

Understanding crustaceans gives insight into evolutionary success in aquatic environments and their critical ecological roles.

Myriapods

Myriapods are remarkable arthropods known for their numerous legs. This group primarily includes centipedes and millipedes. Unlike insects or arachnids, myriapods possess bodies that are long and segmented, with each segment bearing one or two pairs of legs.
Centipedes are typically carnivorous, using their many legs for rapid movement to hunt for food. In contrast, millipedes are generally detritivores, feeding on decaying organic matter.

• Myriapods typically have simple eyes, but their long antennae are crucial for sensing their environment.
• They inhabit moist environments that facilitate their physiological needs, such as breathing since many lack waterproof cuticles.
• Myriapods can defend themselves with secreted fluids or structural features like hardened body plates.

Examining myriapods reveals how varying anatomical features support different survival strategies in arthropod evolution.