Discussion:Chordates 2BIbDF09 10/11

Where do Chordates live ? What do Chordates eat ? How do Chordates reproduce ? How do their bodies work?

Derived Characters Among Vertebrates

several characters allow us to make difference between diffrent species.

At first we have the evolution of jaws who seprates the jawless fishes from all the other vertebrate. Then early bony fishes had lungs, a derived character that permitted lide on land . Amphibians werev the first chordate group to clearly have jointed lims, in the same way that arthopods have joined appendages and to invade the land.. We wiil see that fleshy fins with jointed bones evolved into theses limbs.

The amphibians, reptiles, birds and mammals are tetrapods because they have four limbs: two anterior and two posterior limbs. The amnion, a membrane found in the amniotic egg, evolved in reptiles and is also present in birds and mammals. The special extraembryonic membrane s of the shelle amniotic eggs provided a means of reproduction suitable to land. Such membranes carry out all the functions needed to support the embryo as it develops into a young offspring capable of feeding on its own.