• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Describe how size of living organisms determines the process, structure and function of gas exchange system.

Extracts from this document...

Introduction

Describe how size of living organisms determines the process, structure and function of gas exchange system Organisms rely on diffusion to fulfil their physiological needs. Over time different organisms have adapted so that they can meet their own demands. This is particularly evident in the way gaseous exchange relates to the size of the organism. The organism's oxygen requirements are proportional to its volume i.e. the bulk of the respiring tissue it contains. The exchanges are proportional to the surface area over which diffusion of oxygen can take place. The mathematical rule is - as an object increases in volume the ratio of its total surface area to voulme decreases i.e. The larger the object the smaller it's surface : volume ratio. In small organisms such as protozoa (Amoeba- around 1mm in diameter) ...read more.

Middle

In small organisms the distance is short and does not cause a problem. In larger organisms the distance is larger. This has been overcome by either developing a circulatory system with an oxygen carrying pigment, or by reducing the diffusion distance so that none of the cells are far from the surface. Various organisms have done this in various ways: * Flattened body -e.g. flatworms/leaves on plants - thus reducing the distance between surfaces * Thin tissues - e.g. Hydra - again reducing the distance of diffusion * External medium brought into body - e.g. tracheal system in insects - so that in itimate association is obtained with all tissues. As previously stated amoeba proteus possesses a large surface area to voulme ratio which satisfies its metabolic needs. Many other groups of invertabrate animals such as cnidarians (e.g. ...read more.

Conclusion

In mammals, the use of lungs is adapted. Air moves into or out of the lungs as a result of differences in pressure between atmospheric and alveolar air. When the atmospheric pressure is greater than the pressure within the lungs, air tends to flow down the pressure gradient and inspiration occurs. When the pressure in the lungs is greater than atmospheric pressure, air moves out of the lungs and into the atmosphere. These pressure changes are brought about by changes in the volume of the thorax, which in turn, are produced by contraction or relaxation of the respiratory muscles. The lungs follow these changes passively. The presence of a respiratory pigment in blood further increases the efficiency of the blood's oxygen carrying capacity. Blood that contains any form of respiratory pigment is a more efficient oxygen carrier than one without one. This is because the pigment permits far greater amounts of oxygen to be taken up and transported. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Energy, Respiration & the Environment section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Energy, Respiration & the Environment essays

  1. Marked by a teacher

    Investigation on the size of Limpets.

    5 star(s)

    Where growth is fast, such as on a sheltered shore, the lifespan can be 4 to 5 years while in places of slow growth this can be up to 15 to 17 years. The limpet species Patella vulgata is said to be a 'protandrous hermaphrodite' as younger individuals are predominantly

  2. The Pancreas is a large gland that forms part of the Endocrine System, but ...

    This level of subjectivity made obtaining results difficult. Advantages & Disadvantages: For this test I can detect no real advantages as it provides subjective results and any results that can be obtained are just qualitative. This leads me to seriously consider the value of performing this test Test 4- Faecal

  1. the role of pathology service

    Urine has hundreds of different body wastes. What you eat, drink, how much you exercise, and how well your kidneys work can affect what is in your urine. More than 100 different tests can be done on urine. A regular urinalysis often includes the following tests.

  2. Why the Body Needs Energy? Every living cell within the ...

    Reference: Class notes hand out 02 / 04 /08 http://health.howstuffworks.com/high-blood-pressure-in-depth.htm Website viewed on 29 / 04 08 Measuring the Blood Pressure Blood pressure is measured as the heart contracts and relaxes * The systolic pressure is measured when the heart ventricles contracts.

  1. High Blood Pressure

    Also those with a family history of high blood pressure are also at risk.[5] For reasons that are not entirely understood, people of Afro-Caribbean and South Asian (India, Pakistan and Bangladeshi) origins are more likely to develop hypertension than other ethnic groups.

  2. Ecology of leaves

    As for the leaves in the light exposed area they don't need to increase there surface area, as there is enough light as photosynthesis is already taking place at maximum effectiveness. Also the surface area is decreased to decrease the evaporation of water.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work