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Osmoregulation and Excretion

Lecture 07

© Pearson Education Australia 2009 Campbell et al. 2009 Biology 8e Fig. 44.14

Dr Tony Haigh 2011

Reading

• Campbell et al. 2009 • Chapter 44

• Themes • Evolution • Organisms interact with their environment exchanging matter and energy • Structure and function are linked at all levels • Feedback mechanism regulate biological systems

2

A Balancing Act

• Regulating water uptake • Regulating water loss • Regulating internal environment • Metabolism depends on balance of

• Organic solutes

• Proteins, amino acids

• Salts

• Na+, Cl-, K+, Ca2+, HCO3© Pearson Education Australia 2009 Campbell et al. 2009 Biology 8e Fig. 42.01

3

Osmolarity

• Total concentration of solutes and salts

• milliOsmoles (mOsm)

• High concentration

= high osmolarity

• Low concentration

= low osmolarity

• Water flows from

• Low osmolarity to high osmolarity • Opposite to osmolarity gradient

© Pearson Education Australia 2009 Campbell et al. 2009 Biology 8e Fig. 44.02

4

Osmoregulation

• Water flows against osmotic gradient • Osmoregulation achieved by

• • • • Controlling intake Regulating loss Excreting unwanted solutes Retaining desirable solutes

• • • •

Osmoregulators Osmoconformers Stenohaline Euryhaline

5

Osmoconformers

• • • • Most marine invertebrates Sharks, rays Lungfish, hagfish Internal osmotic environment

≈ external osmotic environment ≈ 1,000 mOsm

• Isoosmotic • Internal composition

≠ external composition

• Ionic regulation...