AP 5

Name the 4 different evolutionary times when levels of oxygen where high

Origin of 1st animal body plans 600mya, movements of animals onto land 400mya, gigantism in arthropods 300mya and increase in mammalian body size

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What were the main characteristics of air breathing evolution

Lungs evolved in late silurian and devonian with fluctuations in rainfall acting as a selection pressure in favour of this

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When where the 3 times that there were low o2 on earth

Mass extinction in late devonian, permian triassic mass extinction and triassic-jurassic mass extinction

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How are lung and swimbladders similar in function and evolution?

Both have evagination of gut tube and both originate from same 7-8 pharyngeal pouches, both have 9th brachial artery blood supplies

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How are lung and swimbladders different?

Lungs venous return to the blood is seperate from general circulation, however swimbladders blood drains into the general circulation

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How is surfactant different in fish and land mamals?

In fish its a fluid mixture with high cholesterol and unsaturated phospholipids but in land mammals its a low cholesterol and unsaturated phospholipid mixture with high levels of desaturated phospholipids

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Name the 6 possible explanations for the evolution of air breathing

Cambrian explosion, silurian-devonian o2 spike, permain o2 decrease and extinction, triassic explosion and mass extinction, jurassic low o2 period and the cretaceous extinction and aging of mammals

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How have vertebrate air breathing organs evolved? (4)

origin of central nervous oscillator, use of posterior pharynx to breathe air, specilisation of dorsal/ventral pharyngeal regions of gas exchange and the differentiation of 2/4 pump breathing cylce

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