Give reasons for the following :
(a) Fish are cold blooded animals.
(b) Small intestine has villi.
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A) Well, poikilothermy is primitive, in the fact that the first vertebrates were (and are) poikilothermic. But as you’ll see, poikilothermy is actually a very elegant solution to the fundamental problem of retaining heat in an aquatic environment—where life first evolved.
Water is a heat sink. Because of its high specific heat, water tends to drain the heat out of surrounding objects. This makes sense, right? If not, go take the polar bear plunge in your winter clothes and read this again.
So, being immersed in water 24/7 would quickly drain the energy of any endotherm (unless it possesses massive amounts of insulating fat like whales and seals). Plus, fishes’ blood has almost direct contact with their heat-robbing environment—through the gills. So for fishes, this means that using your metabolism to keep warm would be very energetically expensive.
In that sense, poikilothermy represents an evolutionary advantage, rather than a disadvantage.
But there are a few endothermic fish species…
Many fishes, such as tuna, actually have a physiological mechanism that enables them to be at least partially endothermic. They use a counter-current circulatory system called the rete mirabile (Latin for “wonderful net”), which exchanges venous blood (going to the heart) and arterial blood (going from the heart). This minimizes the amount of heat that is lost between the fish’s warm, fast moving extremities and its cooler, slow-moving core.
And very recently, scientists discovered the first fully endothermic fish. The Opah keeps its blood warm by constantly flapping its pectoral fins. A series of counter-current heat exchangers in the fish’s gills helps the blood stay warm. This helps the Opah in the deep, cold waters of the Pacific where it lives.
B) To increase the surface area for absorption.
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Adira.
Water is a heat sink. Because of its high specific heat, water tends to drain the heat out of surrounding objects. This makes sense, right? If not, go take the polar bear plunge in your winter clothes and read this again.
So, being immersed in water 24/7 would quickly drain the energy of any endotherm (unless it possesses massive amounts of insulating fat like whales and seals). Plus, fishes’ blood has almost direct contact with their heat-robbing environment—through the gills. So for fishes, this means that using your metabolism to keep warm would be very energetically expensive.
In that sense, poikilothermy represents an evolutionary advantage, rather than a disadvantage.
But there are a few endothermic fish species…
Many fishes, such as tuna, actually have a physiological mechanism that enables them to be at least partially endothermic. They use a counter-current circulatory system called the rete mirabile (Latin for “wonderful net”), which exchanges venous blood (going to the heart) and arterial blood (going from the heart). This minimizes the amount of heat that is lost between the fish’s warm, fast moving extremities and its cooler, slow-moving core.
And very recently, scientists discovered the first fully endothermic fish. The Opah keeps its blood warm by constantly flapping its pectoral fins. A series of counter-current heat exchangers in the fish’s gills helps the blood stay warm. This helps the Opah in the deep, cold waters of the Pacific where it lives.
B) To increase the surface area for absorption.
Thank you!
Hope my answer helps you!
PLEASE MARK ME AS BRAINLIEST
Regards,
Adira.
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