What are the two major groups of arthropods?

The two major groups of arthropods are indeed insects and arachnids. Arthropods represent a vast and diverse phylum that includes organisms characterized by their exoskeleton, segmented bodies, and jointed appendages. Within this phylum, insects make up the largest group, with their complex life cycles, distinct body structures (head, thorax, abdomen), and significant ecological roles. Arachnids, which include spiders, scorpions, ticks, and mites, are another prominent group within arthropods, distinguished by having eight legs and two main body segments (the cephalothorax and abdomen).

Understanding the classification of arthropods is essential for pest management and biological control strategies, as different groups exhibit unique behaviors, life cycles, and responses to pesticides. The other options mentioned do not represent valid groups within the arthropod classification, as mammals and reptiles are vertebrates, whereas amphibians are a separate class entirely, further emphasizing the importance of recognizing the correct classification of insects and arachnids within the arthropod phylum.