ZOL2601 Comparative Animal Physiology summaries made form the prescribed textbook (Schmidt-Nielsen, K. 1997. Animal Physiology. Five Edition: Cambridge University Press:
London.)
Class notes Respiration Animal Physiology, ISBN: 9780521570985
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University of South Africa (Unisa)
ZOL2601 - Comparative Animal Physiology (ZOL2601)
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ZOOLOGY SUMMARIES
ZOL2601
Use the study guide for diagrams
,RESPIRATION
Process of oxygen uptake and release of carbon dioxide is called respiration
Diffusion may be aided by bulk movement such as the movement of air in and out of the lungs but the
concentration gradients remain as the fundamental driving force for moving the respirator gases
Easy access to oxygen in the atmosphere permits a high rate of metabolisms and a high degree of
organizational development
HOW WATER AND AIR DIFFER AS RESPIRATION MEDIUMS
BREATHING MEDIUM: ATMOSPHERE
Composition of dry atmospheric air
Physiologically most important gases: oxygen, carbon dioxide and nitrogen
Nitrogen and the noble gases are equally inert to the organism
Analysis of respiratory gases is usually carried out y determining oxygen and carbon dioxide
values and calling the remainder “nitrogen”
Composition of the atmosphere remains extremely constant
Open atmosphere has a constant gas composition, except for its water vapor
Composition is maintained as a balance between the use of oxygen in oxidation processes
Primarily oxidation of organic compounds to carbon dioxide and the assimilation of carbon
dioxide by plants which in the process release oxygen
COMPOSITION OF DRY ATMOSPHERIC AIR
COMPONENT %
Oxygen 20.95
Carbon Dioxide 0.03
Nitrogen 78.09
Argon 0.93
Total 100
,The greenhouse effect
Carbon dioxide alters the absorption of solar radiation in the atmosphere
Atmosphere is more transparent to incoming shot-wave radiation than to long-wave radiation
emitted by the earth
Outgoing long-wave radiation is absorbed in the atmosphere mainly by carbon dioxide and
water vapor
Doubling of the atmospheric carbon dioxide content would increase by 1.3C if the atmospheric water
remained constant. Would cause extensive melting of the polar ice covers and a rise in the ocean level of
20 to 30m
At higher temperature the atmosphere can hold more water vapor, which enhances the
blanketing effect and causes an increase in temperature rise
Micro-environments, such as borrows occupied by animals have more variable air composition (oxygen
as low as 15%). Air contained in soil in open spaces between the soil particles is often low in oxygen. The
reason is that soil may contain oxidizable material that can severely deplete oxygen. Not only organic
matter and substances such as iron sulfide can consume oxygen until practically all free oxygen has been
removed. Oxidation processes depend on temperature, humidity and other factors
Water vapor in air
Pressure of water vapor over a free water surface changes with temperature
If the atmospheric pressure is lower, water boils at a lower temperature
When air is saturated with water vapor, we say that the relative humidity (r.h) is 100%
Altitude and atmospheric pressure
At an altitude of 3000m humans begin to fell the effects of altitude as a reduction in physical
performance and at 6000m most humans can just barely survive
At sea level the partial pressure of oxygen in dry air is 21.2 kPa
At 6000m the atmospheric pressure is half that at sea level, 50.7 kPa
Decrease in partial pressure of oxygen that produces such severe effects
If person is places at an atmospheric pressure of 47 mm Hg (19 000m) their lungs would be filled
with water vapor and no air or oxygen could enter their lungs
, BREATHING MEDIUM: WATER
Many small organisms obtain oxygen by diffusion through their body surfaces without having any special
respiratory organs and without circulating blood, larger and more complex animals often have
specialized surfaces of gas exchange and also a blood system to transport oxygen more rapidly than
diffusion alone can provide
HOW ORGANSIMS RESPIRE IN WATER
ORGANISMS WITHOUT SPECIALISED RESPIRATORY ORGANS
Simplest geometrical shape of an organisms is a sphere. Sphere has the smallest possible surface
corresponding to a given volume. Any deviation from the spherical shape gives a relative enlargement of
the surface area
Necessary oxygen tension at the surface, sufficient to supply the entire organism with oxygen by
diffusion can be calculated from an equation developed by E. Newton Harvey
𝑉 𝑟
𝐹 =
6𝐾
FO2 is the concentration of oxygen at the surface expressed in fractions of an atmosphere
VO2 is the rate of oxygen consumption as cm3of oxygen per cm3 tissue per minute
r is the radius of the sphere n centimeters
K is the diffusion constant in square centimeters per atmosphere per minute
Conclusion, organisms to be supplied with oxygen must either be much smaller or have a much
lower metabolic rate
Organisms that are supplied with oxygen by diffusion only, protozoans and flatworms are mostly quite
small (less than 1 mm) or have very low metabolic rates like jellyfish
Jelly fish can be very large it may contain less than 1% organic matter, the rest is water and salts
ORGANISMS WITH RESPIRATORY ORGANS
If the respiratory surface is turned out, forming an evagination the resulting organ is usually called a gill
The gill may be enclosed n a cavity such as in fish, this does not change the act that gills
fundamentally are evaginations
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