Lecture Twelve: Evolution of Lungs Flashcards
What increases in the respiratory system as vertebrates transition to land? Why?
Surface area of gas exchange.
Compensate for increased metabolic rate.
What are the two different evolutionary pathways for lungs?
Alveolar
Faveolar
Describe the basic functioning of alveolar lungs
Air enters a closed-end sac, the sac expands then deflates as air is exhaled out. Change in volume with every breath cycle.
Describe the basic functioning of faveolar lungs
Flow-through system (think: straw). Air flows over respiratory surface without changing the volume.
Which lung type is more efficient? What is the hypothesis as to why this is the case?
Faveolar.
Evolved earlier when O2 concentration was lower.
What ecological niche do faveolar lungs open?
High altitude flying.
What type of current is used for faveolar lungs?
Cross-current flow (90* angle).
Why is cross-current flow in faveolar lungs more efficient than flow in alveolar lungs?
It’s more random in alveolar lungs (vessels surrounding sacs), cross-current is more clearly directed so the diffusion gradient is better maintained.
Synapsid
One temporal opening in the skull
Diapsid
Two temporal openings in the skull
Anapsid
No temporal opening.
Found in turtles. Categorized under diapsid since anapsid developed later from that category.
Why aren’t the faveolar and alveolar lungs examples of convergent or parallel evolution?
Their CA had lungs.
As lungs developed, what other changes occurred to the respiratory tract?
Distinct trachea with cartilaginous reinforcement.
In the synapsid lineage, some ribs are lost. What does this lead to the development of?
Diaphragm - used to ventilate lungs.
How does the pressure system change for respiration from gills to lungs?
Positive pressure (push air into) to negative pressure (vacuum).
Negative pressure system
Creates a vacuum by expanding volume.
What does the sternum prevent?
Ribs from opening too much.
Is negative or positive pressure more efficient? Why?
Negative pressure.
Allows for eating and respiring to happen at the same time.
Do synapsid vertebrae numbers change with size? What about sauropsid?
Synapsid: No
Sauropsid: Yes
How does movement affect alveolar lungs?
Same volume in both lungs. Movement enhances respiration.
Animal expands: air pulled in, animal contracts: air pushed out
How does movement affect faveolar lungs?
Lung contracts on side being bent toward, expands on side being lengthened (sprawling gait). Movement can impede efficiency.
As complication of muscle and skeleton increase, what also increases?
Complication of nervous and vascular systems.
Two chambered heart becomes a three then four chambered heart. What does this lead two?
Two pathways in the circulatory system. LP Blood goes to the lungs, returns to the heart, and then is pumped to the rest of the body at higher pressure (combat gravity).
How is blood returned to the heart?
Muscular activity
