Vertebrates cont'd

Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata

We've been talking about the subphylum, Vertebrata. Vertebrates are all members of the phylum, Chordata. What does it mean to be a chordate? Chordates have bilateral symmetry, meaning if cut down the middle, one side would match the other. Chordates also have a notochord and at some point in their lives had gills slits. In fish, the gill slits become gills, but in other animals the gill slits disappear.

There are a few characteristics of vertebrates that make them special. The first is that they have an endoskeleton (bones on the inside). Vertebrates also have spinal cords, backbones, and usually eyes, nostrils, and a mouth on their head.

Vertebrates are either endothermic or ectothermic. Being endothermic means you must keep your own body temperature. This requires energy and the body working around the clock to do so. Being ectothermic means your body temperature is determined by the outside temperatures. Birds and mammals are endothermic. Amphibians, reptiles, and fish are ectothermic.

Some vertebrates give live birth, some lay eggs, and some do both. Birds and amphibians just lay eggs. Reptiles and fish lay eggs and give live birth. Most people think that mammals only give live birth, but there are 2 species that lay eggs, the platypus and echidna. Reptile eggs are different from other eggs because they are leathery and hard making them waterproof. Bird eggs are also tough, but not waterproof. Fish and frogs lay their eggs in the water.

There are 3 groups of mammals: monotremes, marsupials, and placental. Monotremes are the mammals that lay eggs. Marsupials carry their young in a pouch like kangaroos, opposums, koalas.Placental animals give live birth and the babies are grown inside the mother's body being nourished by a placenta.

There are 3 types of fish: cartilaginous, jawless, and bony.