Physical Constraints in Sensory Ecology
5
relationship with its environment, and this, in tum, leads to changes in both kinds
of inputs. Thus, organisms are often engaged in chains of causation that cycle
between these categories of inputs and outputs:
sensory ~ behavior ~ sensory ~ ~ ~ behavior ~ causal ~ ~ ~ fitness
Understanding why an organism responds to a particular sensation with a
particular behavioral response (i.e. the function of the sensory system and the
behavior) requires knowing the causal input later in the chain; and understanding
how the sensory input is amplified and how it controls behavior (i.e. its
mechanism) requires knowledge of physiology. Thus sensory ecology must be
intimately involved with ecology, behavior, and physiology, as well as evolution.
2.3 Information Is Important
The laws of thermodynamics require that all organisms must obtain causal inputs,
including energy and nutrients, but there is no such requirement for obtaining
information. A fundamental characteristic of information is that it is easily ignored;
it causes nothing to happen unless special mechanisms are present to amplify its
effects. Consequently, sensory ecology might have covered only minor,
idiosyncratic aspects of biology, and this probably was the case during early
phases of evolution. However, we observe among extant organisms: (1) large
investments in sensory systems in many bacteria and most animals, (2) frequent
modification of external features (camouflage) to alter visual information, (3) daily
vertical migration among many pelagic animals probably driven by visual
predation (Mangel and Clark 1988), (4) bacteria that transmit signals (by
bioluminescence) to vertebrates, (5) bacteria that communicate with one another
by chemicals (quorum sensing) (Surette et al. 1999), and ( 6) flowering plants that
make significant investments in sending signals to their pollinators. These
observations demonstrate that during evolution, many (most? all?) organisms have
found it advantageous to obtain information about their environment. In fact, one
might conjecture that all extant organisms have some kind of sensory system and
obtain some kind of information about their environment.
Whether or not this conjecture is true, it is clear that information about the
external environment is an important resource to many organisms and especially to
the large animals most familiar to us. There is also an accumulating body of work
suggesting that plants obtain much more information about their environment than
previously realized (Baldwin and Schultz 1983; Rhoades 1985; Kasperbauer 1987;
Bradbume et al. 1989; Balian~ et al. 1990). Thus the study of the processes by
which information is obtained (sensory ecology) is an important part of biology,
and this is increasingly recognized as the development of electronic technology
5
relationship with its environment, and this, in tum, leads to changes in both kinds
of inputs. Thus, organisms are often engaged in chains of causation that cycle
between these categories of inputs and outputs:
sensory ~ behavior ~ sensory ~ ~ ~ behavior ~ causal ~ ~ ~ fitness
Understanding why an organism responds to a particular sensation with a
particular behavioral response (i.e. the function of the sensory system and the
behavior) requires knowing the causal input later in the chain; and understanding
how the sensory input is amplified and how it controls behavior (i.e. its
mechanism) requires knowledge of physiology. Thus sensory ecology must be
intimately involved with ecology, behavior, and physiology, as well as evolution.
2.3 Information Is Important
The laws of thermodynamics require that all organisms must obtain causal inputs,
including energy and nutrients, but there is no such requirement for obtaining
information. A fundamental characteristic of information is that it is easily ignored;
it causes nothing to happen unless special mechanisms are present to amplify its
effects. Consequently, sensory ecology might have covered only minor,
idiosyncratic aspects of biology, and this probably was the case during early
phases of evolution. However, we observe among extant organisms: (1) large
investments in sensory systems in many bacteria and most animals, (2) frequent
modification of external features (camouflage) to alter visual information, (3) daily
vertical migration among many pelagic animals probably driven by visual
predation (Mangel and Clark 1988), (4) bacteria that transmit signals (by
bioluminescence) to vertebrates, (5) bacteria that communicate with one another
by chemicals (quorum sensing) (Surette et al. 1999), and ( 6) flowering plants that
make significant investments in sending signals to their pollinators. These
observations demonstrate that during evolution, many (most? all?) organisms have
found it advantageous to obtain information about their environment. In fact, one
might conjecture that all extant organisms have some kind of sensory system and
obtain some kind of information about their environment.
Whether or not this conjecture is true, it is clear that information about the
external environment is an important resource to many organisms and especially to
the large animals most familiar to us. There is also an accumulating body of work
suggesting that plants obtain much more information about their environment than
previously realized (Baldwin and Schultz 1983; Rhoades 1985; Kasperbauer 1987;
Bradbume et al. 1989; Balian~ et al. 1990). Thus the study of the processes by
which information is obtained (sensory ecology) is an important part of biology,
and this is increasingly recognized as the development of electronic technology