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Comparing Various ClosedCirculatory SystemsMammals Frogs Fish

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Circulation in Mammals (and birds)Double circulation

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Questions1a) How many of each kind of chamber does a

frog's heart have?

b) Compare and Contrast the functioning of thefrogs heart with that of a mammal.

c) The diagram of the path of circulation in a frog

(above) shows that there is an extensive blood

supply to the body wall. Frog's skin is usuallymoist. Frogs can spend considerable time under

water. How could this type of circulation be an

advantage when the frog is underwater?

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FrogDouble Circulation

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FROG: Circulatory System

Answers1a) How many of each kind of chamber does a frog's heart have?Three chambers: 1 Ventricle and 2 Atria

b) Compare and Contrast the functioning of the frogs heart with that of amammal.

They are similar in that both have a right and left atria that function toreceive blood and pump it to the ventricle (s).

But they differ in that oxygen rich and poor blood mix in the ventricleof the frog and the ventricle functions to send blood with a relativelylow oxygen concentration (compared to in a mammal) to the tissuesof the body.

Mammals dont have blood returning from the body and the lungsmixing; they are kept in separate ventricles and so only oxygen richblood from the left ventricle is distributed to the tissues of the body.

So Blood moving to body tissue will contain less oxygen per unit ofvolume than mammalian blood

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Cont.c) ..How could this type of circulation be an

advantage when the frog is underwater?

Oxygen (from the water) can be absorbedacross the moist skin of the frog when it is

under water (and cant use its lungs for gas

exchange). (Oxygen enables aerobic

respiration to proceed and thus ATP to beproduced without waste such as lactic acid

accumulating.)

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FISH

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Questions2 a) How many of each type of chamber does the heart of afish have?

b) Fish have a single circulation as compared to the double

circulation of mammals. Examine the diagram of thepath of circulation in a fish (above) and explain what ismeant by a single circulation.

c) Suggest a possible advantage of a double circulatorysystem over a single circulatory system.

d) Why is a single circulatory system effective for a fish,when it would be ineffective for a mammal?

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FISH: Circulatory System Question

2a) How many of each type of chamber does the heart of a fish have?

1 atrium and 1 ventricle

b) Fish have a single circulation as compared to the double circulation

of mammals. Examine the diagram of the path of circulation in afish (above) and explain what is meant by a single circulation.

Blood moves through the heart only once in each complete circuitaround the body. It goes from heart to gills and from gills to therest of the body. (as opposed to double circulation which involves

the blood passing through the heart twice in each completecirculation of the body. It is returned to the heart after beingreoxygenated at the lungs, before being pumped to the rest of thebody)

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c) Suggest a possible advantage of a double circulatory system over asingle circulatory system

(i) The heart receives blood which is oxygen rich. The heart is a muscle

and muscle tissue being active requires a rich supply of oxygen so thatATP can be generated during aerobic respiration

(ii) Freshly oxygenated blood will then be pumped by the heart to othertissues of the body. This pumping forces the blood along and ensuresrapid delivery to tissues.

(single circulation in comparison means the actual heart tissue onlyreceives oxygen poor blood and that blood pumped to other tissues is

under low pressure and is delivered fairly inefficiently

d) Why is a single circulatory system effective for a fish, when it would beineffective for a mammal.

Fish are poikilothermic ectotherms (their body temp fluctuates with thatof the environment and they dont adjust their production of metabolicheat) and less metabolically active than mammals. Thus their tissues

require less ATP to fulfill their needs, thus oxygen and glucose can besupplied at a slower rate for the respiration to still be sufficient.Mammals are homeothermic endotherms (maintain a stable coretemperature and control generation on metabolic heat to do so) andmore metabolically active and need to supply oxygen and glucose tocells more efficiently to enable supply of ATP fast enough to sustaintheir cells