Gill arches

Question 1

What is the watchmaker analogy? And the blind watchmaker?

Answer 1

The watchmaker analogy is the theory for which there’s someone that has created everything, since nature itself proves the existance of an intelligent designer (God).

The blind watchmaker is the opposite theory, in which evolution is guided by natural selection which provide direction.

To support the theory of a watchmaker, people often use the complexity of some biological structures, which can’t be magically formed but they need an intelligent designer to be created. This idea is thrown off by the fact that complex structure evolved step by step, and not all in one time.

Question 2

What is evolutionary tinkering?

Answer 2

Evolutionary tinkering is the theory for which evolution elaborates on what is already there.

Question 3

How did pharyngeal arches develop?

Answer 3

Pharyngeal arches are the evolutionary result of the pharyngeal basket present in the Amphioxus: initially it was a system of slits, supported by arches in the lateral pharynx, with the function of filtration.

These pharyngeal arches then develop in pouches:

• in fish these pouches open to the outside (pharyngeal clefts); the first cleft form the spiraculum, while the other forms the gills.
• in mammals, the first pouch form the eustachio tube and the middle ear.

Question 4

What is the fate of pharyngeal arches in various animal species?

Answer 4

1. first arch:
   
   • skull, allosphenoideum
   • malleus and incus
   • mandibula jaw
2. second arch:
   
   • stylohyoid ligament
   • stapes
3. third arch:
   
   • corpus hyoideum
4. fourth arch:
   
   • cartilage of larynx