Chapter 1

Animal Physiology

Physiology helps us understand:-The fundamental biology of all animals-Human health and disease-The health and disease of nonhuman animals of importance in human affairs

Figure 1.1 Pacific salmon

migrating upriver to their

spawning grounds 

Figure 1.2 The study of

physiology integrates

knowledge at all levels of

organization 

Figure 1.2 The study of

physiology integrates

knowledge at all levels of

organization (Part 1)

Figure 1.2 The study of

physiology integrates

knowledge at all levels of

organization (Part 3)

Physiology’s Two Central Questions About How Animals Work

What is the mechanism by which a function is accomplished?

Origin: How did that mechanism come to be?

The mechanism of light production

by fireflies (Photinus) 

Figure 1.3 The mechanism of

light production by fireflies

(Photinus) (Part 2)

Natural Selection: the increase in frequency of genes that produce phenotypes that raise the likelihood that animals will survive and reproduce

Adaptation: a physiological mechanism or other trait that is a product of evolution by natural selection

Adaptive Significance: Why the trait is an asset – why natural selection favored the evolution of a trait

Terms to Know

Male fireflies employ their

mechanism of light production for an

adaptive function: mate

attraction

Structures that are similar in gross appearance,

functional performance, and adaptive significance can differ dramatically in details of how they are assembled and work

Mechanisms and adaptive significance are distinct concepts that do not imply each other

The mechanisms by which animals perform their life sustaining functions.

The evolution and adaptive significance of physiological traitsThe ways in which diverse phylogenetic groups of animals

both resemble each other and differThe ways in which physiology and ecology interact, in the

present and during evolutionary timeThe importance of all levels of organization – from genes to

proteins, and tissues to organs-for the full understanding of physiological systems

Topics this Semester

AnimalsEnvironmentsEvolutionary Processes

Three Major Topics

1. Structurally dynamic2. Organized systems that

require energy to maintain organization

3. Both time and body size are fundamental significance in the lives of all animals

Animals

The atoms of their bodies are in dynamic exchange with the atoms in their environments (isotope

studies)

Structurally Dynamic

Although the particular atoms change the overall structure stays the same-

energy required

Animal Organization

Figure 1.6 Conformity and

regulation 

Figure 1.7 Mixed

conformity and regulation in a

single species

Regulation demands more energy than conformity because regulation represents a

form of organization

Homeostatsis – the existence of regulatory systems that automatically make

adjustments to maintain internal constancy

Example: negative feedback – controlled variable brought back to its set point

Changes in response to the external environment:1. Acute Changes – short term, reversible, in individuals2. Chronic Changes – long term, reversible, in individuals3. Evolutionary Changes – alteration of gene frequencies (genotypes) over

the course of multiple generations in population exposed to new environments

Changes in response to the internal environment:4. Developmental changes – programmed changes from conception to

senescence5. Changes controlled by periodic biological clocks-changes that occur in

repeating patterns

Five Time Frames in Which Physiology Changes

Figure 1.8 Heat acclimation in

humans as measured by

exercise endurance 

Acclimation – chronic response to a laboratory environment – controlled environment with just a few changes

Acclimatization – chronic response to a natural environment (winter/summer, high/low elevation)

Norm of Reaction – Correspondences between phenotypes and environments (high melanin & high sun), can be adaptations

Phenotypic Plasticity – the ability of an animal to express two or more genetically controlled phenotypes,

can evolve

Developmental changes – programmed changes from conception to senescence

Changes controlled by periodic biological clocks-changes that occur in repeating patterns

Changes in response to the internal environment

Body Size – Many traits vary in regular ways with their body size among related species – brain size, heart rate, energy use etc. Scaling – the study of these relationships

Changes in response to the internal environment

Figure 1.9 Length of

gestation scales as a regular

function of body size in

mammals 

Are Mountain Reedbuck and Bushbucks Specialized or Ordinary?

1. Animals2. Environments3. Evolutionary Processes

Three Major Topics

1. Temperature2. Oxygen3. Water

Environments

A measure of intensity of the random motions that the atoms and molecules in the material undergo (high temps=lots of movement)

Temperature

Conformers: Fish in the sea around Antarctica spend their entire lives at body temperatures near –1.9°C

Figure 1.11 Butterfly

biogeography 

Decline in Diversity Towards the Poles

Figure 1.12 A thermophilic

(“heat-loving”) lizard common

in North American deserts 

Need for oxygen due to need for metabolic energy.

Releasing energy from organic compounds (food) release hydrogen.

This is combined with oxygen to form water.

The suitability of an environment depends on availability of O2.

Oxygen

Figure 1.13 Performance in

an O2-poor environment 

High elevations have less oxygen in them due to air pressure being low

Density layering can cut off the O2 supply to the deep waters of a lake 

Universal solvent in biological systemsRequired for blood and all other body fluids to have their proper compositions

Water bound to proteins and other macromolecules as water of hydration required for proper chemical and functional properties

Water

Figure 1.16 Microenvironme

nts in the Arizona desert near Tucson 

The Environment an Animal Occupies is Often a

Microenvironment or Microclimate

Microenvironments in the Arizona desert near Tucson 

At head height air temps approach 50°C in summer and 7°C in winter

In the burrow of a kangaroo

rat at 1 m beneath the soil surface,

temperatures remain

between 15°C and 32°C

Figure 1.17 Microenvironme

nts in deep snow in the far

north

1. Animals2. Environments3. Evolutionary Processes

Three Major Topics

A change in gene frequencies over time in a population of organisms

Not necessarily due to adaptation which occurs due to natural selection

Nonadaptive evolution occurs when gene frequencies change but does not confer a survival or reproductive advantage.

Evolution

Natural Selection: the increase in frequency of genes that produce phenotypes that raise the likelihood that animals will survive and reproduce

Adaptation: a physiological mechanism or other trait that is a product of evolution by natural selection

Adaptive Significance: Why the trait is an asset – why natural selection favored the evolution of a trait

Terms to Know

Processes in which chance assumes a preeminent role in altering gene frequencies.

-Random deaths-Founder effects

Genetic Drift

The control of an allele of a single gene of two or more distinct and seemingly unrelated traits- can lead to nonadaptive outcomes

Pleiotropy

Direct observation

The comparative method – how a function is carried out by related and unrelated species

Studying Adaptation

Figure 1.18 The comparative

method 

Study lab populations over many generations – fruit flies

Single-generation studies of individual variation

Studying Adaptation Cont.

Figure 1.19 Physiological

variation among individuals of a

species 

Creation of variation for study – knock out animals, RNA interference, allometric engineering

Studies of the genetic structures of natural populations - clines

Phylogenetic reconstruction-making family trees from molecular data

Studying Adaptation

There must be genetic diversity of a trait for it to evolve

Evolutionary Potential

Figure 1.20 The effects of

genetic diversity on evolutionary

potential