The heart

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what is the primary purpose of the heart ?
to move substances around the body e.g. oxygen, carbon dioxide and digestive products.
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why don't small oranisms such as unicellular creatures have a circulatory system?
large surface to volume ratio, so diffusion is able to take place fast enough to meet the organisms requirements.
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define diffusion ?
the movement of molecules or ions from a region of high concentration to a region of low concentration by relatively slow random movement of molecules.
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why can't multicellular organisms rely on diffusion?
diffusion can't move substances around their bodies quick enough therefore they rely on a mass transport system instead.
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define mass transport system
is a structure that moves substances efficiently over long distance ny mass flow.
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what is open circulatory system?
is when the heart pumps blood out into cavities surrounding the animals organs. (blood circulates in large open areas)
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what is a closed circulatory system?
where the blood is enclosed within tubes
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what are the common features of a closed circulatory system?
have higher blood pressure, as blood flows along fairly narrow tubes. the blood travels faster and the blood system is more efficient at delivering substances around the body.
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why are you must likely to find closed circulatory systems within larger more active animals?
because the blood travels faster thus more efficient at delivering substances around the body.
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describe the path the blood travels in a closed circulatory system ?
blood leaves the heart under high presure. flows along the arteries and the arterioles. to the capillaries for exchange between blood and cells. to the venules and then to the veins. and finally back to the heart.
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define a single circulatory system?
where the blood flows through the heart once for each complete circuit of the body.
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define a double circulatory system?
when the blood flows through the heart twice for each complete circuit.
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animals with a double circulatory system usually have what?
A high metabolic rate. as the heart gives the blood returing from the lungs an extra boost reducing the time it takes for the blood to circulate around the body, delivering more rapildly to the cells to meet their needs.
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define mass flow
the process where liquids and all the particles contained inthe circulatory system are transported in one direction due to the difference in pressure.
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Card 2

Front

why don't small oranisms such as unicellular creatures have a circulatory system?

Back

large surface to volume ratio, so diffusion is able to take place fast enough to meet the organisms requirements.

Card 3

Front

define diffusion ?

Back

Preview of the front of card 3

Card 4

Front

why can't multicellular organisms rely on diffusion?

Back

Preview of the front of card 4

Card 5

Front

define mass transport system

Back

Preview of the front of card 5
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