This document discusses homeostasis and the factors that influence an animal's internal environment. It explains that most animal cells are exposed to the internal environment rather than the external one, and that animals must actively regulate their internal conditions through homeostasis. It also notes that the composition of dry atmospheric air is extremely constant, with oxygen, nitrogen, and carbon dioxide making up the majority, and that increases in carbon dioxide from fossil fuel use can impact the greenhouse effect and global climate.

1. HOMEOSTASIS
Dr. NAGABHUSHAN C M M.Sc., B.Ed., Ph.D
ASSISTANT PROFESSOR
DEPT OF STUDIES IN ZOOLOGY,
VSK UNIVERSITY, BALLARI
91-9880-121-090
nagabhushancm@vskub.ac.in

2. An animal is defined by its
organization.
This characteristic of animals
provides the most fundamental
reason why animals require
inputs of energy throughout life
the second law of
thermodynamics says that for
organization to be maintained in
a dynamic system, use of energy
is essential.
Most cells of an animal are
exposed to the internal
environment, not the external
environment
Dr. Nagabhushan CM
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3. Dr. Nagabhushan CM
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External temperature
internal
temperature
External temperature
internal
temperature
(OC)
(OC)
An animal’s internal
environment may be
permitted to vary when its
external environment
changes
An animal’s internal
environment HELD
CONSTANT

4. 4
Dr. Nagabhushan CM

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Dr. Nagabhushan CM

6. COMPOSITION OF DRY ATMOSPHERIC AIR remains EXTREMELY CONSTANT
PHYSIOLOGICALLY MOST IMPORTANT
GASES are
O 20.95 %
N 78.09 %
CO2 00.03 %
Ar 00.93 % (noble gases=0.002%
+ minute Methane + pollutant gases)
_______
in addition it contains water vapour
This composition of air is maintained as a balance between the
user of oxygen in oxidation processes (respiration) and
assimilation of carbon dioxide by plants in which oxygen is
released (photosynthesis).
Do use of fossil fuel- oil, coal, gas deplete
the atmospheric oxygen ?
in 1910 accurate oxygen analysis showed the
value of 20.948 % and in 1970 repeated measure showed
20.946 %.
the investigators then calculated that if all the
known recoverable FF reserves were depleted, there
would still be 20.8 % Oxygen left in the atmosphere.
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Dr. Nagabhushan CM
Physiologically this change would be of no
consequence: it would be no more than the
change in oxygen partial pressure .

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• Slight increase in carbon dioxide by FF have negligible physiological
effects (not harmless)
• BUT the slight change in CO2 alters the absorption of solar radiation in
the atmosphere and may have unpredictable GHE which drastically
change climatic conditions.
Atm is more TRANSPARENT to incoming short-wave
radiations than to the long-wave radiations emitted by
earth.
The out going radiations are absorbed by CO2 and H2O
vapour. (if conc of CO2 is doubled = increased world
temp. by 1.3 oC if atm water remained constant)

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CARBON DIOXIDE (33%)
METHANE (15%)
OZONE (13%)
CFCs (07%)
N2O (06%)
OTHER CAUSES

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Carbon Dioxide (CO2)
A direct result of fossil fuel combustion, CO2 is arguably the most important
greenhouse gas, on the basis of both the amounts produced and its effects on
the climate (Bloom 2010). The majority of CO2 produced by human activities
stays in the atmosphere, while some also enters aquatic ecosystems.
Carbon dioxide levels are approximately 380 ppm (parts per million), but are
expected to reach 535–983 ppm by 2100 (IPCC 2007).
(Approximate contribution to global warming: 33%; Hansen & Sato 2001).

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Methane (CH4)
Under oxygen-poor (anaerobic) conditions, microorganisms frequently produce
CH4. Methane is also produced by: the imperfect combustion of wood products
(clearing land for agriculture), animals (digestive by-products of cattle, goats,
sheep), and natural gas operations (natural gas is primarily CH4) (Bloom
2010).
Methane levels are approximately 1.8 ppm, but future levels are predicted to
be from 1.46–3.39 ppm by 2100 (IPCC 2007).
(Approximate contribution to global warming: 15%; Hansen & Sato 2001).

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Ozone (O3)
Tropospheric ozone, as opposed to stratospheric ozone (i.e., the “ozone layer”),
is a secondary pollutant. One of the main components of photochemical smog, it
is generated through complex chemical reactions that involve sunlight, nitrogen
oxides (NOx), carbon monoxide (CO), and volatile organic compounds (VOCs)
(Bloom 2010).
All of these compounds are produced through by fossil fuel combustion.
Tropospheric ozone levels may increase by 40–60% by 2100 (IPCC, 2007).
(Approximate contribution to global warming: 13%; Hansen & Sato 2001).

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Chlorofluorocarbons (CFCs)
Molecules of carbon atoms bound to chlorine and fluorine atoms.
used in diverse ways such as refrigerants, spray can propellants, cleaners, and in
the production of Styrofoam (Bloom 2010).
These compounds break down the ozone layer; chlorine atoms can break down
multiple ozone molecules (Withgott & Brennan 2009).
While tremendous progress has been made to reduce the production of these
compounds, they have a lifespan in the atmosphere of 20–100 years, and the
potential to increase global warming 1000-times more than a similar mass of
CO2 molecules (IPCC 2007; Bloom 2010).
(Approximate contribution to global warming: 7%; Hansen & Sato, 2001).

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Nitrous Oxide (N2O)
Most nitrous oxide is produced by microorganisms undergoing anaerobic
respiration (denitrification). Large fertilizer additions, a common agricultural
practice, increase these emissions (Bloom, 2010).
Nitrous oxide levels are approximately 0.32 ppm, but future levels are predicted to
be 0.36–0.46 ppm by 2100 (IPCC 2007).
(Approximate contribution to global warming: 6%; Hoffman et al. 2006).

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• Extensive Melting Of Polar Ice Cover
• Rise In The Ocean Level (20-30 m or MORE)
• Loss Of Coastal Lands
• Major Cities Along The Shoreline
• Higher ATM Temp Can Hold More Water Vapour
Enhancing The Blanketing Effect  Further Rise In Temp.
• However increased H2O vapour in the ATM may augment
formation of CLOUDS  PROTECTS from incoming
solar radiations = OPPOSITE EFFECT.

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• Burrows , open spaces between soil particles have
variable air composition
• 15 % oxygen or even less
• 05 % increased CO2 conc.
• Reason: soil may contain oxidizable material that can
severely deplete the oxygen.
• Rich FeS can also consume oxygen until exhaustion.
• These oxidation processes depend on temperature;
humidity; rain water and other factors.
(ex. Rains blocks the soil porosity and provide
HUMIDITY for increased oxidation & the
microatmosphere may change drastically.

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solubility of gases