Introduction

Rhythmicity is found in a multitude of biotic and abiotic factors. The examples of environmental cycles shown in Table 1 document the wide range of frequencies of cycling abiotic factors. Some environmental cycles have well-known effects on organisms - such as the rhythmic change in foraging behavior of intertidal organisms caused by the ebb and flow of the tides. Other cycles, such as the change in the path of the Earth's revolution around the Sun (the orbital eccentricity rhythm), can potentially affect organisms by causing slow weather changes over thousands of years. A few well-known biological rhythms - some of which are and some ofwhich are not controlled by environmental cycles - are listed in Table 2. Biological rhythms involve repetitive processes ranging in frequency from more than once per second, such as the spontaneous firing rate of neurons in the mammalian central nervous system, to less than once every decade, such as the oscillation in the wild population of the Canadian lynx (Lynx canadensis).

Most research on biological rhythms conducted during the past 50 years has dealt with daily/circadian and annual/circannual rhythms and has concentrated on

Table 1 Some environmental cycles on the Earth

Duration of

cycle

Phenomenon

2 x 10~15s

Oscillation of electromagnetic waves in visible

2 x 10~2s

light

Voltage oscillation in alternated current (home

electricity)

12.4h

Tides (attractive forces of the Sun and the

Moon)

24 h

Days (Earth's rotation)

30 days

Months (Moon's revolution around the Earth)

365 days

Years (Earth's revolution around the Sun)

10 years

Cycle of sunspots

22 000 years

Precession of the equinoxes

41 000 years

Variation in Earth's obliquity (axial tilt)

96000 years

Variation in Earth's orbital eccentricity

Table 2 Some biological rhythms

Duration of

cycle

Phenomenon

10~1 s

Spontaneous firing rate of cortical neuron

1s

Human heart rate

1h

Pulsatile secretion of hormones

12.4h

Tidal and circatidal rhythms

24 h

Daily and circadian rhythms

4 days

Estrous cycle of rat

7 days

Human work-rest week

30 days

Lunar and circalunar rhythms

110 days

Estrous cycle of elephant

12 months

Annual and circannual rhythms

10 years

Oscillation in the wild population of Canadian

lynx

basic behavioral, physiological, neural, and molecular processes studied in a small number of species in the laboratory. Few studies have examined interspecies differences in basic processes, and fewer yet have addressed ecological issues in natural environments. Thus, this article will start with a brief review of what has been learned in the laboratory about the basic processes of biological rhythmicity and will then examine what little we know about the behavioral ecology of biological rhythms.

Trash To Cash

Trash To Cash

This book will surely change your life due to the fact that after reading this book and following through with the steps that are laid out for you in a clear and concise form you will be earning as much as several thousand extra dollars a month,  as you can see by the cover of the book we will be discussing how you can make cash for what is considered trash by many people, these are items that have value to many people that can be sold and help people who need these items most.

Get My Free Ebook


Post a comment