Chp 1 Function on the Ecological Stage. Animal Physiology: Study of how animals function Importance:...
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Transcript of Chp 1 Function on the Ecological Stage. Animal Physiology: Study of how animals function Importance:...
Animal Physiology: Study of how animals function
Importance: - For basic understanding of physiology since human are
part of the animal kingdom- Important practical applications for health and disease,
management
Mechanism and Origin: Physiology’s two central questions
- What is the mechanism by which a function is accomplished?
- How did the mechanism originate?
The importance of physiology
• The study of mechanism: How do modern day animals carry out their functions? study or organ, cell functions and metabolism
• The study of origin: Why do modern-day animals possess the mechanisms they do? they inherited it from ancestors + it was beneficial adaptation through selection
• Mechanism and adaptative significance are distinct concepts that do not imply each other: Adaptation can be achieved through different mechanisms
This book’s approach to physiology
• Physiological mechanisms can be explain from a combination of evolutionary origin, environmental adaptations
• Environmental physiology: • Mechanistic physiology: study of mechanism• Evolutionary physiology: study of evolutionary origins
• Comparative physiology: compare the physiology of various groups
• Environmental physiology: study of the physiological responses to changes in environment
All of these approaches are interrelated
Animals
• Molecules forming an animal are constantly changing• The structure of an animal (organ system) persists
through time• The cells are exposed to the internal environment
- The internal environment might be permitted to change with the external environment conformity
- The internal environment might be kept constant despite varying external environments regulation
Homeostasis: internal constancy critical to maintain proper function
• Claude Bernard: recognized the constancy of the internal environment
• “Constancy of the internal environment is the condition for free life”
• Walter Cannon (1871-1945) – introduced the term “homeostasis = coordinated physiological processes which maintain most of the constant states in the organism”.
• Homeostasis is critical to mammals, but it is not important for survival in some other groups
• Regulation and conformity have their own advantages/disadvantages:
- Regulation: Costs energy but permits cells to function in a constant internal environment despite changing external conditions
- Conformity: Cells are subjected to changes when external environment changes. However, if they survive it, the energy cost is minimal.
Time in the lives of animals
1- physiological responses to change in external environment
2- internally programmed changes of physiology
3- evolutionary responses: at the level of populations
• (1) Responses to changes:- Acute responses: responses
within minutes- Chronic responses: long term
changes to the physiology- Acclimation: physiological
responses to small changes in the environment
- Acclimatization: responses to a larger change in the environment (ex: winter and summer)
2- internally programmed changes of physiology
• Phenotypic plasticity: phenotypic changes that an individual (single genotype) can undergo with changing environment
• Internally programmed changes: genetically programmed: can be due to development or to biological clocks
- development: Hb expression
- biological clocks:
- daily rhythm
- seasonal rhythm ..
The importance of body size
• Size determines many functions (scaling):
- gestational time
- rate of energy use
- age of sexual maturity
Environments• All the chemical, physical, and biotic components of an
organism’s surroundings.• Earth’s major physical and chemical environments:- Temperature: -70oC in Antarctica to 50oC in some deserts
most tissues are killed at temp>45oC
- Oxygen: 21% O2 in air, less in soil, high altitude, low solubility in water
- Water: universal solvent. Is the place of origin of life.- Blood of marine invertebrates has a similar composition to sea-
water (SW). Osmosis effect if water salinity changes
- Presence of microenvironments and microclimates- Animals modify their environments
Evolutionary processes
• Evolutionary physiology: study of the origin and maintenance of physiological traits
• Some processes are adaptive (due to natural selection), others are not (= founder effect -due to genetic drift)
• Pleiotropy: when a trait is common in a population because it is closely correlated with another trait favored by selection
The study of adaptations• Comparative method: today
animals are the products of yesterday life. We inherited the adaptations
• Studies of laboratory populations over many generations
• Single-generation studies of individual variation
• Creation of variation for study• Study of the genetic structure of
natural populations• Phylogenetic reconstruction
• Evolutionary potential depends on the available genetic variation