1.1 Physical Constraints in Sensory Ecology
David B. Dusenbery
School of Biology, Georgia Institute of Technology, Atlanta, Georgia 30332 USA
Abstract
A "big picture" of sensory ecology is developed. The logic of biological
investigation and the meaning of behavior and information are briefly addressed
along with the importance of information to organisms. Ties between sensory
ecology and physiology and behavior are stressed. The value of understanding
physical constraints on what is possible is emphasized. The simplest physical
environment is that of planktonic organisms living free of any surface, and
consequences of physical constraints and biological generalities are described for
such organisms, as examples. This provides new insights into why small bacteria
are not motile, why most chemotactic bacteria are rods employing temporal
mechanisms of comparison for gradient detection, why small planktonic animals
do not employ pheromones for mate attraction, and explaining why male and
female mating types are common among sexually reproducing species.
Key words Noise, signal, information, threshold, plankton
1 Introduction
Organisms are extremely complex mechanisms, and it is a challenge to gain even
glimpses of understanding how they work. Jumars (1993, Preface) has pointed out
that biologists generally tend to focus on the particular and ignore general
relationships. This is unfortunate, because science should always strive for the
most general understanding possible. This chapter attempts to place sensory
ecology in the "big picture", to describe how it relates to other fields of biology,
and to discuss some of the general relationships important to the field.
A fundamental question that must be addressed for any biological feature studied
is whether organisms possess the feature because it is of adaptive value or whether
it is accidental in the sense that it is a sideeffect of some other adaptation, an
adaptation to a previous condition that no longer exists, or a pure accident of
genetic drift and fixation during evolutionary history.
David B. Dusenbery
School of Biology, Georgia Institute of Technology, Atlanta, Georgia 30332 USA
Abstract
A "big picture" of sensory ecology is developed. The logic of biological
investigation and the meaning of behavior and information are briefly addressed
along with the importance of information to organisms. Ties between sensory
ecology and physiology and behavior are stressed. The value of understanding
physical constraints on what is possible is emphasized. The simplest physical
environment is that of planktonic organisms living free of any surface, and
consequences of physical constraints and biological generalities are described for
such organisms, as examples. This provides new insights into why small bacteria
are not motile, why most chemotactic bacteria are rods employing temporal
mechanisms of comparison for gradient detection, why small planktonic animals
do not employ pheromones for mate attraction, and explaining why male and
female mating types are common among sexually reproducing species.
Key words Noise, signal, information, threshold, plankton
1 Introduction
Organisms are extremely complex mechanisms, and it is a challenge to gain even
glimpses of understanding how they work. Jumars (1993, Preface) has pointed out
that biologists generally tend to focus on the particular and ignore general
relationships. This is unfortunate, because science should always strive for the
most general understanding possible. This chapter attempts to place sensory
ecology in the "big picture", to describe how it relates to other fields of biology,
and to discuss some of the general relationships important to the field.
A fundamental question that must be addressed for any biological feature studied
is whether organisms possess the feature because it is of adaptive value or whether
it is accidental in the sense that it is a sideeffect of some other adaptation, an
adaptation to a previous condition that no longer exists, or a pure accident of
genetic drift and fixation during evolutionary history.