September 7th, 2012 Biol 225

Chapter 40: Basic Principles of Animal form and function

Anatomy= biological form

Physiology= biological function

Animals are diverse:

In morphology & physiology

Niches they occupy

Despite of diversity they share many features and face similar challenged

Unity and diversity

Natural selection has driven the evolution of animals that are well suited for their environment

Structure and function

Animals don’t maintain all aspects of their internal environment every time.

40.1: Animal form and function are correlated at all levels of organization

Animals with simple internal organization have body plans that enable direct exchange between almost all their cells and the external environment.

Animals with flat shaped body plans have more exposure to the surrounding areas.

Most animals have complex internal organization, so

A multicellular organization works only if every cell has access to a suitable aqueous

environment, either inside or outside the animal’s body.

As body size increases, the muscles required for locomotion must represent an even

larger fraction of the total body mass and thicker skeletons are required to maintain

adequate support.

Integral body fluids link exchange surfaces to body cells

Interstitial fluid= fluid that fills the spaces between cells

Circulatory fluid: i.e. blood

Exchange between interstitial fluid and circulatory fluid allows cells to obtain nutrients

and get rid of wastes.

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Exchange occurs as substances dissolved in an aqueous solution move across the

plasma membrane of each cell.

Exchange surfaces are long & branched (folded) to allow maximum nutrient absorption.

i.e. lungs, kidney, small intestines.

Cells tissues organs organ system

Tissues= groups of cells with a similar appearance and a common function

Organs= tissues organized into functional units

Epithelial tissues:

o Cover the outside of the body and line organs and cavities within the body

o Form active interfaces with environment

o Polar (2 different sides)

Apical: luman (cavity)

Basal: separates the epithelium from underlying tissue.

Connective tissue:

o Holds many tissues and organs together and in place

o Cells in extracellular matrix. In the matrix there are:

Fibroblasts: secrete fiber proteins

Macrophages engulf foreign particles and any cell debris by

phagocytosis.

o 3 types:

Collagenous fibers: provide strength and flexibility

Reticular fibers: join connective tissue to adjacent tissue

Elastic fibers: make tissues elastic

Muscle tissue: all muscles cells consist of filaments containing actin & myosin

(proteins that enable muscle contraction)

o 3 types:

Skeletal muscle:

Responsible for voluntary movement

Attached to bones by tendons

Smooth muscle: responsible for involuntary body movements

Cardiac muscle: contractile wall of heart

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Nervous tissue

o Reception, processing, transmission of info

o 2 types

Neurons: transmit nerve impulses

Glial cells (glia): support cells

40.2: Feedback control maintains the internal environment in many animals

Regulator= uses internal mechanisms to control internal change in the face of external

fluctuation. Body temperature is independent of water temperature.

Conformer= allows its internal condition to change in accordance with external changes

in the variable.

Homeostasis= maintenance of internal balance. In achieving homeostasis, animals

maintain a relatively constant internal environment even when the external environment

changes significantly

An animal achieves homeostasis by maintaining a variable, such as body temperature

or solute concentration, at or near a particular value, or set point. Fluctuations in the

variable above or below the set point serve as the stimulus detected by a receptor, or

sensor. Upon receiving a signal from the sensor, a control center generates output that

triggers a response, a physiological activity that helps return the variable to the set

point.

Feedback control in Homeostasis:

Negative feedback: control mechanism that reduces or “damps” the stimulus.

Positive feedback: control mechanism that amplifies the stimulus.

Alterations in homeostasis: the set points and normal ranges for homeostasis can

change under various circumstances. Some regulated changes are associated with a

particular stage in life (puberty), others are cyclic (menstrual cycle).

Circadian Rhythm= set of physiological changes that occur roughly every 24 hours.

One way in which the normal range of homeostasis may change is through

acclimatization= the gradual process by which an animal adjusts to changes in its

external environment. (temporary, it’s not like adaptation)

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40.3 Homeostasis processes for thermoregulation involve form, function and behavior.

Thermoregulation= The process by which animals maintain an internal temperature

within a tolerable range.

Endothermic= animals that are warmed mostly by heat generated by metabolism.

Internal sources provide most of the heat for temperature regulation.

Ectothermic= Animals that gain most of their heat from external sources to provide most

of the heat for temperature regulation.

Homeothermic= maintain relatively constant body temperature (i.e. humans)

Poikilothermic= referring to organisms whose body temperature varies with the

temperature.

Most endotherms are homeotherms. Most ectotherms are poikilotherms.

How does thermoregulation work?

Balancing heat loss and gain

o Conduction: the direct transfer of thermal motion (heat) between

molecules of objects in direct contact with each other.

o Convection: the mass movement of warmed air or liquid to or from the

surface of a body or object

o Radiation: the emission of electromagnetic waves by all objects warmer

than absolute zero.

o Evaporation: the process by which a liquid changes into a gas

Heat moves from hotter objects to colder objects

Metabolic activity can also be a source of heat (endotherms)

Control the exchange and generation of heat (BOOK)

o Insulation: reduces heat exchange (there’s always some heat exchange)

(i.e. fur, feather)

o Cooling by evaporative heat loss (i.e. sweating, panting in dogs)

o Behavioral responses

o Adjusting metabolic heat production

September 7th, 2012 Biol 225