orgin of fins

Question 1

fossil evidence? what did fins first look like? appeared in?

Answer 1

• Little fossil evidence
  
  • First appeared as phalanges, fin-like ridges, folds
  • Eventually formed paired fins
  • First appeared in the ostracoderms (agnathans)

Question 2

what are the 3 hypotheses for origin of fins?

Answer 2

fin fold theory, gill arch hypothesis, fin spine hypothesis

Question 3

describe fin fold theory

Answer 3

○ Fins come from continuous fleshy folds (like in ostracoderms)

Question 4

describe gill arch hypothesis

Answer 4

○ Unlikely, arches from ectoderm vs fins mesoderm

○ Innervation also somatic not visceral

Question 5

describe fin spine hypothesis

Answer 5

○ Early pectoral/pelvic spines with flesh membrane
○ Later evolved weak fin rays
○ Best supported hyothesis

Question 6

how do fins increase stability?

Answer 6

1. Increased stability and balance
   • Unpaired fins (dorsal and anal) control
   • Rolling (=rotation around body axis)
   • Yawing (=side to side motion)
   • Paired fins (pectoral and pelvic) control
   ○ Pitch (=vertical motion)

Question 7

how do fins increase manuverability? provide lift?

Answer 7

2. Increased maneuverability 
	• By altering angles of fins 
	3. Fins provide lift 
	• Hydrofoil like 
		○ Resist forces that displace a fish moving through 3-D space

Question 8

how do fins provide defense? communication?

Answer 8

fins can include toxins, give visual signals with color and movement `

Question 9

types of visual communication via colors?

Answer 9

nuputal, aposematic, cryptic, disruptive

Question 10

summary jaws and fins

Answer 10

increased locomotion and food habits, increase lifestyle and niches, increased diversity