THE VARIETY OF LIVING ORGANISMS

Organism Adaptations

Organism Adaptations

Mass transport

When materials have to travel over long distances this is carried out efficiently through mass transport. Both plants and animals contain mass transport systems. In plants you find:

  • gaseous exchange
  • water transport

In animals examples of mass transport include:

  • gaseous exchange
  • blood transport
  • endocrine system
  • excretion

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Unicellular organisms

For unicellular organisms gases can simply diffuse across the cell membrane. This means that there’s no need for a specialised gas surface. Unicellular organisms have a large surface to volume ratio; in other words: they have a bigger surface area compared to their volume. In addition, being composed of only one wall the path of diffusion is small. This makes them efficient for gas exchange.

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Multicellular organisms

Multicellular organisms are much larger than unicellular ones and so gaseous exchange becomes more difficult.

For large, thin organisms, like flatworms, the surface area to volume ratio has remained high and so they can still use their outer body as an exchange surface.

However, larger organisms have had to create more specialised exchange surfaces.

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Gas exchange

In order to achieve gas exchange, organisms have developed different systems.

However, one process they all use is diffusion. In order for diffusion to be most efficient it requires:

  • a large surface area
  • a thin surface
  • a concentration gradient

The larger the area, the thinner the surface, and the bigger the concentration gradient, the quicker the rate of diffusion.

Other factors, for example an oxygen transport system to take oxygen where it’s needed, are also involved. Plus, temperature has an effect on the rate on diffusion: it speeds up with warmer conditions because the molecules have more energy and so can move more quickly.