Chp 1Function on the Ecological Stage

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