Predators & defenses : Many different types of animals prey on adult sea urchins, including birds, sea otters, fishes, crabs, lobsters, octopuses, and sea stars. Eggs and larvae of sea urchins are eaten by many types of carnivorous zooplankters and by suspension-feeding invertebrates including hydroids, sea anemones, and mussels, just to name a few.
IPv4 (Internet Protocol Version 4) is the fourth revision of the Internet Protocol (IP) used to to identify devices on a network through an addressing system. The Internet Protocol is designed for use in interconnected systems of packet-switched computer communication networks (see RFC:791).
Packet switching is a philosophy of network communication, not a specific protocol. The protocol used by the Internet is called TCP/IP. The TCP/IP protocol is due to Robert Kahn and Vint Cerf. The IP in TCP/IP stands for Internet protocol and is the protocol used by computers to communicate with each other on the Internet. Computers using the Internet must have IP software. Packets that follow the IP specification are called IP datagrams. These datagrams have two parts: header information and data.