THIS IS ALL ABOUT SQUIDS!!! Q-1) How might the reflective tissue aid the squid i
ID: 2218 • Letter: T
Question
THIS IS ALL ABOUT SQUIDS!!!Q-1) How might the reflective tissue aid the squid in its variedhabitats?
Q-2) Describe how the gills change in thewater. When you first placed them in water they seemed to have noform. Do they have a form now? Describe them. Explain how this formwould be advantageous for gas exchange. (Hint: Consider the conceptof surface area:"Now that the gills are in the water, do theyappear to be bigger than you expected?)
Q-3) What is the benefit of having two heartsnear the gills? Why not just send the blood from the gills straightto the various tissues? Why return it to another heart?
Q-4) What feature in humans would be mostsimilar to the pen? What function do you think the penserves?
Explanation / Answer
Gills of vertebrates are developed in the walls of the pharynxalong a series of gill slits opening to the exterior. In fish, thegills are located on both sides of the pharynx. Gills are made offilaments which help increase surface area for oxygen exchange. Inbony fish, the gills are covered by a bony cover called anoperculum. When a fish breathes, it opens its mouth at regulartimes and draws in a mouthful of water. It then draws the sides ofits throat together, forcing the water through the gill openings.The water passes over the gills on the outside. Valves inside themouth keep the water from escaping through the mouth again. Theoperculum can be very important in adjusting the pressure of waterinside of the pharynx to allow proper ventilation of the gills.Lampreys and sharks lack an operculum, they have multiple gillopenings. Also, they must use different methods to force water overthe gills. In sharks and rays, this ventilation of the gills isachieved either by the use of spiracles or ram ventilation(ventilation by constantly swimming). Although some animals usethis method it is much better for animals to use a spiracle becausethey are less susceptible to injury.
In most species, a countercurrent exchange system is employed toenhance the diffusion of substances in and out of the gill, withblood and water flowing in opposite directions to each other. Watertaken into the mouth passes out of the slits, bathing the gills asit passes.
Some fish utilize the gills for the excretion of electrolytes.Gills' large surface area tends to create a problem for fishseeking to regulate the osmolarity of their internal fluids.Saltwater is less dilute than these internal fluids; as aconsequence, saltwater fish lose large quantities of waterosmotically through their gills. To regain the water, they drinklarge amounts of seawater and excrete the salt. Freshwater is moredilute than the internal fluids of fish, however, so freshwaterfish gain water osmotically through their gills.
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