2
David B. Dusenbery
An important approach in answering this question is to consider what
alternatives to the existence of the feature are possible. In other words, how is the
evolution of organisms constrained? There are two basic types of constraints: (1)
Since organisms evolve from preexisting organisms, the specific history of
previous evolution provides one set of constraints. (2) Organisms must live in a
particular environment governed by certain physical relationships, and the laws of
physics and chemistry provide another set of constraints.
Even the understanding of evolutionary history requires sorting out adaptive
changes in the past from the effects of genetic drift, and physical constraints are a
major source of adaptive pressure - in the past as well as the present. Since all
evidence indicates that the laws of physics and chemistry have remained
unchanged since the beginning of life on earth, determining how these laws
constrain evolutionary adaptations will help answer questions about both past and
present adaptations.
The constraints of evolutionary history are difficult to determine and limited by
the fact that they apply to only one lineage. In contrast, some physical constraints
are universal, and understanding their implications provides powerful insights,
applicable to all organisms. For example, the limited rate of diffusion in liquid
water provides a strong constraint on the maximum size of organisms without
special transport systems (Dusenbery 1996, pp.6-9; Withers 1992, pp. 571-572).
Similarly, recognizing the conservation of atoms and energy and the second law of
thermodynamics has provided powerful insights to understanding cellular
metabolism, organismal physiology, and ecosystem processes. In sensory biology,
understanding the laws of optics has similarly provided powerful insights into
understanding many features of the eyes of vertebrates and insects and the
differences between them (Land 1981 ).
What can be done in sensory ecology to exploit physical constraints to reveal
general relationships that will improve understanding? In previous work, I
illustrated how understanding physical constraints on how stimuli move through
the environment (Dusenbery 1992, pp. 49-87) provides insights into the potential
range (Dusenbery 1992, p. 239) and relative costs of communication by different
modalities (Dusenbery 1992, p. 327).
In this chapter, I review some more recent analyses of physical constraints on
small organisms dispersed in water and hopefully provide inspiration for others to
exploit this approach further. First, however, let us consider what the field of
sensory ecology encompasses.
2 What Is Sensory Ecology?
2.1 Information and Causation
All individuals interact with two kinds of "spaces" - a pool or flow of genetic
information (contained in a population of similar organisms) and a material
environment (consisting of both animate and inanimate components, with which
David B. Dusenbery
An important approach in answering this question is to consider what
alternatives to the existence of the feature are possible. In other words, how is the
evolution of organisms constrained? There are two basic types of constraints: (1)
Since organisms evolve from preexisting organisms, the specific history of
previous evolution provides one set of constraints. (2) Organisms must live in a
particular environment governed by certain physical relationships, and the laws of
physics and chemistry provide another set of constraints.
Even the understanding of evolutionary history requires sorting out adaptive
changes in the past from the effects of genetic drift, and physical constraints are a
major source of adaptive pressure - in the past as well as the present. Since all
evidence indicates that the laws of physics and chemistry have remained
unchanged since the beginning of life on earth, determining how these laws
constrain evolutionary adaptations will help answer questions about both past and
present adaptations.
The constraints of evolutionary history are difficult to determine and limited by
the fact that they apply to only one lineage. In contrast, some physical constraints
are universal, and understanding their implications provides powerful insights,
applicable to all organisms. For example, the limited rate of diffusion in liquid
water provides a strong constraint on the maximum size of organisms without
special transport systems (Dusenbery 1996, pp.6-9; Withers 1992, pp. 571-572).
Similarly, recognizing the conservation of atoms and energy and the second law of
thermodynamics has provided powerful insights to understanding cellular
metabolism, organismal physiology, and ecosystem processes. In sensory biology,
understanding the laws of optics has similarly provided powerful insights into
understanding many features of the eyes of vertebrates and insects and the
differences between them (Land 1981 ).
What can be done in sensory ecology to exploit physical constraints to reveal
general relationships that will improve understanding? In previous work, I
illustrated how understanding physical constraints on how stimuli move through
the environment (Dusenbery 1992, pp. 49-87) provides insights into the potential
range (Dusenbery 1992, p. 239) and relative costs of communication by different
modalities (Dusenbery 1992, p. 327).
In this chapter, I review some more recent analyses of physical constraints on
small organisms dispersed in water and hopefully provide inspiration for others to
exploit this approach further. First, however, let us consider what the field of
sensory ecology encompasses.
2 What Is Sensory Ecology?
2.1 Information and Causation
All individuals interact with two kinds of "spaces" - a pool or flow of genetic
information (contained in a population of similar organisms) and a material
environment (consisting of both animate and inanimate components, with which