Answer:
1. Invertebrates as a group do not have a specific classification. Since vertebrates are classified by the chordate subphylum vertebrata, invertebrates are any other animal that is classified outside of that class. Are there a lot of invertebrate species? Mammals, amphibians, reptiles, fish, and birds all have vertebrae.
2. This decline matters because of the enormous benefits invertebrates such as insects, spiders, crustaceans, slugs and worms bring to our day-to-day lives, including pollination and pest control for crops, decomposition for nutrient cycling, water filtration and human health.
3. Arachnids are members of a class of animals that includes spiders, scorpions, mites, and ticks. What they all have in common—and what distinguishes them from insects—are four pairs of legs and no antennae.
