Lecture Six: Chondrichthyes Continued, Transition to Osteichthyes Flashcards
February 11
What is ecological role defined by?
Where an organism is found and what they feed on.
The shape of proteins and lipids can be altered by what underwater factor?
Pressure.
What categorizes a shark as “ancient”?
Having more than 5 gill slits.
Before what depth are most sharks found?
3000m.
What is the difference between buoyancy and floating?
Buoyancy: Maintain level in the water column.
Floating: Stay on top of water.
How does an oily liver provide buoyancy?
Oil is less dense than water.
Ram ventilation:
Swimming with mouth open so water flows over the gills. Used by sharks when activity level/metabolic rate increases.
Do all sharks have to move to survive?
No, not all.
What does the swim bladder evolve into as animals move to land?
Lungs.
Why does the swim bladder evolve?
Transition from cartilage endoskeleton to bony endoskeleton. Skeleton becomes denser, fish need another way to stay buoyant.
What are some major differences between Osteichthyes and Chondrichthyes?
- Endoskeleton (cartilage -> bone).
- Fixed fin placement (pectoral fins move up, pelvic fin moves forward, etc. in oste).
- Heterocercal tail to homocercal tail (propel fwd).
- Subterminal jaw -> terminal jaw.
- Gill slits -> operculum cover covers all gills.
- placoid scales -> flexible cycloid or ctenoid scales.
Operculum cover
Covers all gills in Osteichthyans. Used for buccal pumping (pouring water over gills).
What change accompanies the development of the operculum cover?
More musculature around head region to use the cover.
What types of fish are ganoid scales found in?
More ancient fish like the sturgeon. Usually not very flexible.
Spiral valve:
Found in Chondrichthyes. Used to increase SA in intestine for digestion.
How do Osteichthyes increase digestive surface area?
Lengthen the intestines.
Rectal gland:
Found in Chondrichthyes.
Used to get rid of excess salt.
Describe Osteichthyan circulation.
2 chambered heart.
Blood from the heart flows to the gills to be oxygenated then goes to the rest or the body before circulating back to the heart.
Do fish have high or low blood pressure? Why (3 reasons)?
Low.
Blood flows from the heart to the gills, which are very fragile. If the pressure is too high, the gills will be damaged.
Oceanic environment offsets gravity so high blood pressure is less important.
When the fish swims, blood is naturally pumped back to the heart which raises BP. Heart is actually used to help slow it back down.
Vehicle pumping:
Movement of operculum cover to move water over the gills.
Describe the salt vs. solute regulation in Chondrichthyes.
Chondrichthyes: Same SOLUTE concentration in body and environment. No net flow of water in/out. Uses energy (osmoregulate to osmoconform). Lower SALT content in bodies than environment (will diffuse in) – why they have rectal gland.
Which is more complex: Osteichthyes or Chondrichthyes osmoregulation?
Chondrichthyes.
Placoid scales allow for what kind of water flow?
Laminar (water flows smoothly, little/no turbulence created).
In water, does more or less of the body moving prevent friction?
Less movement. (Stiff body is better).
