Final answer:
Horseshoe crabs are described as ancient, marine, armored survivors, with descriptions based on objective facts. Jointed limbs and segmentation contribute to the success of the Arthropod group, while soft shell crabs are a result of the molting process. Horseshoe crabs' breeding behavior on shores gives insights into the early Arthropods' transition from ocean to land.
Step-by-step explanation:
Words to describe horseshoe crabs could include ancient, marine, armored, and survivors. These words are based on an objective reading, considering that horseshoe crabs have existed for around 450 million years, live in marine environments, have a hard exoskeleton for protection, and have survived multiple mass extinction events.
Jointed limbs are significant for Arthropods because they allow for complex movement and specialization, leading to a variety of appendage adaptations. These adaptations, along with segmentation, have been key to the success of Arthropods. They enable diverse functions ranging from locomotion to feeding, which allows them to inhabit various ecological niches.
Soft shell crabs are actually crabs that have recently molted their old exoskeleton and are still soft before their new shell hardens. Crustaceans need to shed their outer skeletons through a process called molting in order to grow. The carapace is the hard, protective upper shell of crustaceans like crabs and lobsters.
Scientists studying horseshoe crabs believe that their behavior of coming ashore to breed provides clues as to why Arthropods first left the ocean. This behavior is driven by tidal rhythms and is observed in other marine arthropods as well.