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Summary Adaptation Physiology of Animals (NWI-BM010C)
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Extensive summary of all lectures of adaptation physiology of animals (NWI-BM010C).
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Adaptation Physiology of AnimalsHomeostasis and allostasis
Adaptation → should be genetic and inheritable to the next generation
Animal Adaptation Physiology
- Adaptation → a heritable physical or behavioral trait that serves a specific purpose function
and improves an organism’s fitness or survival
Time frames in which physiology changes
Physiological responses to the environment
- Adaptation sensu stricto usually takes a long time, occurs over generations, and is non-
reversible
o Adaptation: evolutionarily, genomically-fixed responses
- Acclimatization (‘fast’, i.e. within the life span of an organism)
- Acclimation: the response to experimental conditions; it tells us about the capacity of an
organism to handle disturbances, within the bandwidth of the genotype and thus its
evolutionary capacity (and success)
- Example: a camel is adapted to desert life, a human being can acclimatize to desert
conditions, or we can force a mouse model to acclimate to desert conditions (called
acclimation)
Evolutionary concepts are related to processes or patterns
- Process, natural selection, which drives adaptation
- Pattern, e.g. the homology of the human arm and a bird wing, structures with similar
underlying bones, modified in shape but not in basic layout
o The tails of say a fish and a dolphin are analogous structures
- Adaptation
o A dolphin is wonderfully adapted to move in water (is adapted to an environmental
factor)
o Biston betularia, melanism in a moth providing camouflage in soot-blackened birch
trees (adaptation in the making)
, o Darwin finches on Galapagos islands: lineages branching out from a common
ancestor, due to different environmental conditions prevailing in the different
geographic locations (adaptation, adaptive radiation); beak form adapted to
available food resources
Adaptation
- Consider the degree of environment-specificity of adaptations
o The nature of selection favoring and adaptation may change over time (exaptation)
o New features that evolve must integrate well with the rest of the bodily structure
and organization (co-adaptation)
- Examples
o The origin of jaws is not environmental-specific, they are very useful under a wide
range of environmental conditions and never got lost. Jaws arose from the skeletal
supports of the first pair of gill supports; gills were enlarged for improved breathing
and then underwent changes for improved eating (an exaptation)
o The cranium and vertebral column are a design improvement in all environments,
never lost in vertebrates; walking legs (tetrapods) and wings (birds) are more
environment-specific. The latter have been lost or reversed (cataceans and penguins,
respectively)
Evolution and adaptation – Darwinism in a nutshell
- Natural selection (for adaptations) is the driving force for evolution
- At least some of the differences between individuals, which impact
their survival and fertility, are inheritable
- During the ‘struggle for resources’, the fittest individuals will survive
(i.e. the frequency of the beneficial gene in the population
increased) and reproduce
Evolution and homeostasis
- Homeostasis and allostasis are the mechanisms/processes required to adapt to a dynamically
changing environment
Concept of homeostasis
- Claude Bernard developed the physiological concept of homeostasis, a fundamental concept
in modern physiology/biology; he noted constancy of chemical composition and physical
properties of body fluids, despite changes in the environment
- He claimed that this ‘fixity of the milieu intérieur’ (mainly blood in his case) compared to the
milieu exterieur was essential to the life of higher organisms
Homeostasis
- A relatively stable state of equilibrium or a tendency toward such a state between the
different but interdependent elements or groups of elements of an organism, population, or
group
- In other words: homeostasis is the property of an open system, especially living organisms
(or parts/organs thereof), to regulate its internal environment so as to maintain a stable
condition, by means of multiple dynamic equilibrium adjustments controlled by interrelated
regulation mechanisms
,Homeostatic control mechanisms
- Key words: stimulus → receptor (sensor) → control center → effector
Examples of homeostasis in the animal body: states of balance in the body
Negative feedback
Positive feedback
- Oxytocin (only known hormone that provides positive feedback)
, Homeostasis
- Homeostasis has survival (i.e. adaptive) value because it means an animal can adapt to a
changing environment, by becoming (partly) independent
- E.g., you can deal with the temperature difference you face when you step out the front door
- The body will attempt to maintain a norm, the desired level of a factor to achieve
homeostasis (setpoint)
- However, it can only work withing tolerable limits; extreme conditions will disable the
negative feedback mechanism, and pathologies may develop
Homeodynamics
- A more recent term that ‘updates’ homeostasis, defined in a dictionary as:
o ‘the pysiologycial process by which the internal systems of the body (e.g. blood
pressure, body temperature, acid-base balance) are actively maintained at
equilibrium, despite variations in the external conditions’
- Homeodynamics attempts to add emphasis to the dynamic, active, ever-adjusting
physiological nature of these processes
There was growing awareness that strict homeostatic control is not always the explanation for
physiological processes: an example…
- Arterial blood pressure (continuous registration) fluctuates to meet predicted demand
o No defense of a setpoint
o Rather responsiveness to rising and falling demand
o
- Arterial pressure fluctuates, even in a subject with established hypertension
o No defense of a fixed setpoint
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