Exchange Of Materials Flashcards

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1
Q

what do all organisms have to do relating to their environments

A
  • they must take in substances that they need from the environment
  • and get rid of any waste products
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2
Q

how can oxygen be an example of how organisms take substances from their environment and produce products to get rid of

A
  • cells need oxygen for aerobic respiration which produces carbon dioxide as a waste product
  • these two gases move between cells and the environment by diffusion
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3
Q

how can water be an example of how organisms take substances from their environment and produce products to get rid of

A
  • water is taken up by cells by osmosis

- in animals, dissolved food molecules and minerals diffuse along with it

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4
Q

how can urea be an example of how organisms take substances from their environment and produce products to get rid of

A
  • urea diffuses from cells to the blood plasma

- for removal from the body by the kidneys

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5
Q

what is dependent on the organisms surface area to volume ratio

A

how easy it is for an organism to exchange substances with its environment

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6
Q

what is urea

A

a waste product produced by animals from proteins

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7
Q

what does a ratio show

A

how big one value is compared to another

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8
Q

how does an organism becoming larger affect the surface area to volume ratio

A

the larger the organism, the smaller its surface area is compared to its volume

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9
Q

what would be the surface area to volume ratio ratio be of a mouse in a 1cm by 1cm block

A
  • surface area is (1x1) x 6 = 6cm^2
  • volume is 1x1 = 1cm^3
  • suface area to volume ratio is 6:1
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10
Q

how do gases and dissolved substances enter single celled organisms

A

gases and dissolved substances can diffuse directly into the cell across the cell membrane

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11
Q

why can a single celled organism have gases and dissolved substances diffuse directly into it

A
  • because they have a large surface area compared to their volume
  • so enough substances can be exchanged across the membrane to supply the volume of the cell
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12
Q

what do multi cellular organisms have compared to single celled organisms

A
  • a much smaller surface area compared to their volume

- or a much smaller surface area to volume ratio

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13
Q

what is the effect of multi cellular organisms having a smaller surface area to volume ratio

A

it makes it difficult to exchange enough substances to supply their entire volume across their outside surface alone

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14
Q

what do multi cellular organisms need if they have a small surface area to volume ratio

A
  • some sort of exchange surface for efficient diffusion

- and a mass transport system to move substances between the exchange surface and the rest of the body

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15
Q

what must the needed exchange surfaces for a multi cellular organism be able to do what have done to be able to do this

A
  • it must allow enough of the necessary substances to pass through
  • so they are adapted to maximise effectiveness
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