Download central themes in physiology

LECTURE 2
CENTRAL THEMES IN ANIMAL
PHYSIOLOGY
Hierarchy of life
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The figure is showing one movement of frog leg
from organism to molecular level
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IN THE EXAMPLE OF FROG ABOVE
Frog catches a passing fly by a leap (skeletal
muscle)
After eating fly, frog’s stomach mixes and
massages the contents (smooth muscles)
The nutrients absorbed into the blood are
propelled by the beating of heart to the body
(cardiac muscle)
SOME EXAMPLES OF STRUCTURE FUNCTION RELATIONSHIP
Transmitter (e.g., hormone) and receptor (just
like Enzyme-Substrate)
Nutrition and digestion (Shape of beak is
according to food available)
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ADAPTATIONS, ACCLIMATIZATION
AND ACCLIMATION
Adaptation is a physiological, biochemical or
anatomic change that typically occurs in a
gradual manner over generation. Generally it is
not reversible.
Physiology of an animal is usually well
matched with the environment. Evolution by
natural selection is the explanation of the
process called adaptation.
Acclimatization
is
a
physiological,
biochemical or anatomic change within and
individual animal during its life that results
from the animal’s chronic exposure in its
native habitat to new, naturally occurring
environmental conditions.
Acclimation is same process but when the
same changes are induced experimentally in
laboratory or in wild habitat by researcher.
Adaptation is a change in genotype that results in a
structural or functional change in phenotype
(expression of genotype).
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ADAPTATION ----CONTD
EXAMPLES:
1. Migration of a bear from low-lying valley to
high mountain result in increased ventilation in
beginning but later on returned to normal as
other physiological mechanisms takes its
place, for example, RBCs increase in number
to increase oxygen-carrying capacity of blood.
This is called Acclimatization.
2. If the conditions of mountain (hypobaric) are
developed in laboratory for any animal, same
response could be seen, but it is called
Acclimation.
3. Bar-headed goose fly up to the peaks of
Himalayas, which if other animals do, they die.
This is adaptation of the goose selected via
process of natural selection to survive in this
extreme environment.
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ADAPTATION ----CONTD
Adaptation was thought to be optimal but now
it is realized that it is not “optimal” all the time
but good enough to ensure survival of the
animal in its environment. For example,
temperature range of 1 -2 °C is adapted; it
could be more precise but may not be selected
by natural selection to ensure survival.
It could be difficult to know that whether a
physiological characteristic is of adaptive
value or not. A physiological process is
adaptive if it is present at high frequency in a
population. The reason is that it results in a
higher
probability
of
survival
and
reproduction.
 How to prove certain character is adaptive? Comparative
approach tells us how it is possible.
 Closely related species have same character while living in
strikingly different environments. Llama and camel’ blood
have same affinity for oxygen (which is very high).
Lives in very cold area (Tibet)
Lives in deserts and plains
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The reason for all this is that both physiological
and anatomic adaptations are genetically based, i.e.
these are in germ line. And these pass from one
generation to the next. Animals inherit information
in the form of DNA. Mutation (spontaneous
alteration) occurs in the nucleotide sequence of
DNA that cause alteration in RNA and then
proteins. Mutations that enhance animals’ survival
and hence chances of its reproduction are retained
by natural selection and their frequency in
population increases over time. This results in
Adaptation.
Genetic material (DNA) is passed from
parents to offspring's
Germ line is derived from the parent’s germ
line, to continue the germ line DNA.
Evolution is centered on the survival of DNA,
since information it have defines a species.
Failure to reproduce its DNA leads to
extinction of a species.
From biological point of view, animal life’s
main purpose is to reproduce and propagate its
DNA. All physiological processes, behaviours
and anatomic structures are ultimately
subservient to continuation of germ line.
Adaptation is to cope with constraints and
demands of environment to survive.
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HOMEOSTASIS
Homeostasis is defined as “consistency of
internal environment”. This is a concept first
recognized by a French pioneer of modern
Physiology, Claude Bernard.
Animals live in quite hostile environments
- Aquatic animals face more dilute (fresh
water) or more salty (sea water) than their
body.
- Terrestrial animals face too hot or too cold
temperature
- Aerial mode of life has resistance to flight
etc
Also most environments have fluctuations, i.e.
changes over time and in seasonal changes.
To survive animals have to cope with these
changes.
Homeostasis is the mechanism for this.
Various physiological processes and anatomic
structures are adapted to maintain homeostasis.
EXAMPLES:
Body Temperature in human
Body pH (in human it is slightly alkaline, 7.4
at 37 °C)
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FEEDBACK CONTROL SYSTEMS
 Feedback control is the basic mechanism by which
systems, whether mechanical, electrical, or
biological,
maintain their equilibrium or
homeostasis.
 In the higher life forms, the conditions under which
life can continue are quite narrow. A change in body
temperature of half a degree is generally a sign of
illness.
 The homeostasis of the body is maintained through
the use of feedback control [Wiener 1948].
 A primary contribution of C.R. Darwin during the
last century was the theory that feedback over long
time periods is responsible for the evolution of
species.
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CONFORMITY AND REGULATION
 Conformity is that organisms cannot maintain
homeostasis when there is a change in
environment and change their internal
environment when external changes.
 Regulation is phenomenon in which organisms
maintain homeostasis and resist change in
external environment.
 Organisms which do not maintain homeostasis
are called conformers and who do so are
called regulators.
 e.g. birds maintain body temperature, hence
called thermoregulators; some annelid worms
cannot maintain oxygen homeostasis, hence
are oxyconformers.
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