Question

1. What are the four chordate shared characteristics (=synapomorphies) and what is the function of each structure for a chordate animal?

2. The evolution of jaws is considered to be a key innovation in vertebrate evolution. What advantage do jawed vertebrates (gnathostomes) have when compared to jawless fishes (agnathan, hagfish and lamprey)?

3. What groups of vertebrates have an amniotic egg? What advantage do amniotes have over non-amniote vertebrates (e.g. fishes and amphibians)?

4. How did the origin of jaws, lungs, limbs, and the amniotic eggs affect the course of vertebrate evolution?

Answer 1

Answer 1) 4 chordate shared characteristics ( synapomorphies) are -

1. Notochord

2. Nerve cord

3. Pharyngeal slit

4. endostyle

Function of each structure for a chordate animal is as follows:

1. Notochord- it is located ventral to the dorsal nerve cord. It's primary function is to provide support and rigidity to the body. It mainly assists in locomotion by providing undalatory movements all because notochord Works as a rod for attachment of muscles.

2. Nerve chor- it is single dorsal hollow. Produced by unfolding of dorsal ectodermal cells. It mainly involves nerve impulse arising from peripheral nervous system.

3. Pharyngeal slits - they are nothing but the opening between pharynx, throat with the outside. Water is filtered by pharyngeal to separate the food particles.

4. Endostyle- it is found in lower chordates. It uses cilia to coat itself with mucus so that it can work to filter food.

A thumbs up would be highly appreciated. Thanking you.