1. What is an Arthropod?

2.  Over the course of animal evolution, a number of changes in the coelomate body plan led to the evolution of animals with even greater complexity.

3.  The first major change in the coelomate body plan to arise was segmentation. Segmentation provided animal bodies with greater flexibility.

4.  Segmentation provided animal bodies with greater flexibility.  It also enabled individual segments to have individual functions. Guts & Reproduction Sensory Muscles

5.  The first segmented animals to evolve were the annelid worms, such as earthworms and leeches.  All coelomate animals except mollusks and echinoderms are segmented.

6.  Biologists say that segmentation underlies the body organization of all advanced coelomate animals.  A second major change in the evolution of the coelomate animal body was the evolution of jointed appendages.

7.  Arthropods were the first animals to have jointed appendages. Arthropods use jointed appendages as legs for walking, wings for flying, antennae to sense their environment, and as mouthparts for sucking, ripping, and chewing their food.

8.  Jointed appendages have proven to be very successful in the animal kingdom – more than half of all named animal species on Earth are arthropods, most of which are insects.