Detail the pathway of oxygenated water in the ventilation of a fish. Name and briefly describe the mechanism by which gaseous exchange takes place.
Oxygen rich water enters the mouthdue to buccal expansion > water is accelerated across the gill filamentsdue to simultaneous contraction of the buccal cavity and expansion of the opercula > gaseous exchange takes place via a countercurrent system.The countercurrent system is the name given to the mechanism used for gaseous exchange in afish, whereby the direction of travel for oxygenated water and blood is opposite. This means that high oxygenatedwater untakes gaseous exchange with already oxygenated blood, while water witha lower oxygen content exchanges will less well oxygenated blood. This networkmaintains an active concentration gradient for a longer period of time.
OF
Related Biology A Level answers
All answers ▸Briefly describe the steps of DNA replication and the enzymes involved.
How are action potentials transmitted across synapses using neurotransmitters such as acetylecholine?
A drug used in a scientific trial is a competitive inhibitor of the elctron transport chain in the light dependent reaction, what affect will this have on the amount of glucose synthesised by the plant? (4 marks)
Compare and contrast the structures and starch and cellulose and explain how these relate to their functions in the cell