Vertebrate Basics
Vertebrates are the most advanced organisms on Earth. The traits that make all of the animals in this section special are their spinal cords, vertebrae, and notochords. It's all about having a series of nerves along your back (dorsal side). If you are an organism, you can't just have the nerves sitting there. You need to give those nerves support and protection. That need brings us to the backbones and a rod of cartilage called the notochord.
Not So Many Species
Fifty thousand species might seem like a lot. Compared to theinvertebrates, there are not that many species of vertebrates. You might be asking why. One reason is that vertebrates are usually larger than invertebrates. They need more space. Another reason is that, even though they are more advanced, there are many limitations on the environments that are available to them.
Think about it this way. If you are smart mammal, would you rather live near the ocean or in the frozen tundra of the arctic? Many land animals can make that decision and move to more desirable areas for living. Those nicer areas can only support so many species of animals.
They've Got The Brains
Vertebrates are smart. Some of them are very smart. We mean you. Most vertebrates have very advanced nervous systems. While a goldfish might not compare to your intelligence, when you compare a goldfish to a sea anemone, a goldfish is like Einstein. Octopi are probably the smartest invertebrates and may equal or be smarter than some vertebrates. Octopi are the exception in the invertebrate category.
More cool traits about vertebrates are that they have muscles and skeletons. While the materials may vary, muscles allow vertebrates to move around very efficiently and perform complex moves. That ability to move and the intelligence to go with it gives vertebrates such as reptiles and birds an advantage in the natural world.
Here Fishy Fishy
Fish have had an evolution all their own. When you think of a fish today, you are actually thinking about an advanced organism. They started their development over 500 million years ago as fish-like organisms without jaws. Over many years they developed bones and skeletons. There are four main types of fish.
(1) Jawless fish: Like we just said, the first fish didn't have jaws. It is tough to eat and even harder to survive in the long run. Even with a mouth and a series of teeth to cling to their food, it's still hard to compete with fish that have jaws and mouths. Some species made it to the modern world. One good example is a Lamprey. These fish suck on the sides of other fish. Not a very exciting life.
(2) Fish with cartilage: In our opinion, though not as advanced as fish with real bones, fish with cartilage are the coolest fish out there. Cartilaginous fish include species of sharks, rays, and skates. Sharks are the ultimate hunters of the ocean. They are big, fast, and have very sharp teeth that rip their prey apart. Skates and rays are a lot more docile or non-aggressive. They are usually bottom feeders. The bodies of rays and skates have developed large wings that allow them to glide through the water using their tail as a rudder.
(3) Bony fish with lobe fins: And then the fish with real bones came along. No longer was cartilage the skeleton of choice. Bony fish were able to out-compete most of the fish that had cartilage for skeletons. Scientists classify them into two groups - the LOBE-finned and the RAY-finned. Lobe-finned bony fish include examples such as lungfish and coelacanthus. Until about 30 years ago, scientists thought the coelacanthus was long extinct. One day a fisherman found one in the net and voila!
