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AMER. ZOOL., 29:1095-1103 (1989)
Natural History and the Necessity of the Organism1
A L A N J . KOHN
Department of Zoology, University of Washington,
Seattle, Washington 98195
SYNOPSIS. Natural history, in focusing on the individual whole organism in its environment, occupies a central position in the spectra of spatial and temporal scales appropriate
to biological science. This essay examines the current status of theory relevant to natural
history, growing points of research within natural history, and its relevance to other
components of biology. During the past 15 years, optimality, especially of foraging, and
biomechanics, especially of individual organism—environment relationships, have been
fruitful hypothetico-deductive approaches to animal natural history. Because of the nested
hierarchical nature of biological organization, knowledge of individual organisms is necessary to understand more complex levels—populations and communities—as well as the
roles of the component parts of organisms. For systematics and evolutionary biology,
individual organisms preserved as specimens in natural history museums document knowledge of the biological world. Type specimens are especially important, as these "name
bearers" that anchor original descriptions document all communication among biologists
about species.
INTRODUCTION
Spatial scales appropriate to the biological sciences range over some 16 orders of
magnitude, from small organic molecules
to the earth's entire biosphere. Biologically
relevant temporal scales span an even
broader spectrum, from nanosecond transport of ions across cell membrane channels
to the 4-billion-year sweep of biological
evolution (Fig. 1). Over this immense
expanse of space and time, the subject matter of biology is appropriately viewed as
levels of organization increasing in complexity, from macromolecule through
organelle and cell to ecological communities and the entire biosphere. This is a
nested hierarchy: at any level, a unit or
system is composed of lower-level subsystems and is a component of a higher-level
system. A cell is a set of organelles; an
organism, a set of functional systems; a
community, a set of populations of different species (Fig. 2).
Most practising biologists concentrate
their research on a single level of organization or on two or three adjacent ones. A
cell biologist may study the structure and
interaction of organelles in a specific cell
1
From the Symposium on Is the Organism Necessary?
presented at the Annual Meeting of the American
Society of Zoologists, 27-30 December 1987, at New
Orleans, Louisiana.
type; a population ecologist may study how
the numbers of individuals in a population
change in time, and how other components
of the community affect these changes.
These examples follow the scheme indicated above, and involve a "hierarchy of
control" (Fig. 2, left) (Grene, 1987). The
integrity and functioning of each unit
depend on information passing in both
directions between it and units at the levels
above and below. Evolutionary biologists
may pursue studies along a somewhat different but overlapping hierarchical scheme
of gene-organism-deme-species- clade (e.g.,
Gould, 1986). Grene (1987) calls this type
a "hierarchy of classification" (Fig. 2, right).
Classification per se lacks the dynamic of
control, but evolutionary processes such as
speciation and extinction invariably affect
lower levels, and more inclusive levels may
also be affected (Vrba and Gould, 1986).
Understanding the nature of interactions
in these types of hierarchy are the most
challenging problems of biology.
Here I adopt Marston Bates' definition:
"Natural history is the study of animals and
plants—of organisms. . . . I like to think,
then, of natural history as the study of life
at the level of the individual—of what
plants and animals do, how they react to
each other and their environment, how
they are organized into larger groupings
like populations and communities" (Bates,
1954). Some may regard natural history
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ALAN J. KOHN
BIOLOGY
earth: areal extent of biosphere
6-
Island of Hawaii
4-
°
earth: radial extent of biosphere
1 km
ORGANISMS
2-
I
•
1 m
w
largest organisms' v
largest animals*
many animalsand plants
0-
smallest vertebrates*
most
• invertebrates
• many protists
-2-
1 mm
protists
-4-
cells
1 jun
prokaryotes
-6-
organelles
2
CO
smallest organisms
viruses, small organelles
proteins
-8-
small molecules
1A -10-
I
-16
1
1
-14
•
1
-12
1 ^second
1
I
-10
1
1
-8
1
1
'
-6
1
'
-4
1 minute
1 day
1
1
1
"
0
-2
1 year
1
2
•
1
4
1
1
6
1 million
years
1
1
'
8
I
10
1 billion
years
x
TEMPORAL DIMENSIONS (TIME IN 10 YR)
FIG. 1. The spatial and temporal domains of biology (outer rectangle) and of natural history—the biology
of whole individual organisms (inner rectangle). Dots indicate relationships between size (linear dimension)
and life span or age to approximate order of magnitude. "Radial extent of biosphere" is from high mountains
to the greatest depth of the sea; "areal extent of biosphere" approximates the square root of earth's surface
area. The island of Hawaii is included to aid appreciation of scale. Based partly on information in Morrison
etal. (1982).
defined this way as a subset of ecology.
Schoener (1986) for example refers to
"individual-ecological concepts—those of
behavioral ecology, physiological ecology,
and ecomorphology." For the purposes of
this essay, "individual-ecologic" concepts
are those of natural history, which also
encompasses much of behavioral ecology
and ecomorphology. I assign the last clause
of Bates's definition to ecology.
Bates (1954) also reminds us that no level
of biological organization is inherently any
more important than any other. Natural
history, however, in focussing on the individual whole organism in its environment,
occupies a central position in the spatial
and temporal scales of life (Fig. 1). This
narrows our focus to about 8 orders of
magnitude each for organism size and for,
say, life span time, still formidable ranges
of scale.
Every organism on earth is potentially
subject to study of its natural history, and
the relevant attributes of organisms are
wonderfully diverse: external appearance,
life history, habits and activities, or more
concisely, life stories and life styles. This
description suggests some main subdivisions: General natural history pertains to
where organisms live and how they make
their livings. Comparative natural history
concerns structural and behavioral adaptations, in the case of animals for e.g., feeding, locomotion, defense and reproduction, across taxa. Evolutionary natural history
concerns the more difficult questions of why
organisms do what they do, or how these
attributes of the whole organism in its environment have come to be. "An important
goal of the study of natural history is the
identification and ranking of selective
agencies" (Vermeij, 1987). The individual
NATURAL HISTORY AND THE ORGANISM
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HIERARCHY OF CLASSIFICATION
HIERARCHY OF CONTROL
Biosphere
Clade
\
I
Ecosystem
\
Community
Species
Den*
Population
Organism
Otgantsrn
Organ System
\
Organ
Cel
Organelle
Maoomctecule - Gene
\
Molecule
FIG. 2. Hierarchies of biological organization. In the hierarchy of control, integrity and functioning at each
level requires information passed between adjacent levels in both directions. "Clade" on the diagram indicates
the entire hierarchy of higher monophyletic taxa. The position of "gene" indicates that it belongs to the
more general set of macromolecules.
organism is an important unit of selection;
an individual survives to reproduce, or it
does not.
In this essay I examine the current status
of some areas of theory relevant to natural
history, the focal level of which is the whole
individual organism in its environment. I
note briefly some empirical and experimental approaches to questions in natural
history and assess the importance and relevance of natural history to other components of biology.
Two hypothetico-deductive approaches
derived from general evolutionary theory,
optimality and biomechanics, seem particularly important in natural history although
in rather different ways, and I present them
as "growing points" of the field. Optimality hypotheses lead to explanations and
predictions about what an organism will
do, i.e., its behavior, given certain
conditions. Biomechanical theory seeks to
explain the organism's design and its activities in relation to its environment in terms
of engineering principles and to predict
the properties of its materials.
OPTIMALITY THEORY IN
NATURAL HISTORY
When we contemplate every complex
structure and instinct as the summing up
of many contrivances, each useful to the
possessor, nearly in the same way as when
we look at any great mechanical invention as the summing up of the labour,
the experience, the reason, and even the
blunders of numerous workmen; when
we thus view each organic being, how
far more interesting, I speak from experience, will the study of natural history
become!. . . (Darwin, 1859)
Optimal foraging
In modern terms, Darwin's desideratum
would apply optimality theory to natural
history. Nearly a century later, David Lack
(1954) showed that observed reproductive
rates of birds and mammals often maximize the number of offspring that survive
to independence. But little more than two
decades have passed since the first explicit
applications of optimality theory to foraging by individual animals (MacArthur
and Pianka, 1966; Emlen, 1966). These
seminal papers, presenting a priori theory
grounded in the assumptions of natural
selection, inaugurated the most active outburst of research in animal natural history
of the past 20 years (Gray, 1987, fig. 1).
MacArthur later (1972) called optimal
foraging theory the economics of consumer choice, and it is typically modeled
as a decision-making process based on ben-
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ALAN J. KOHN
efit-cost assessment. The animal is predicted to select food items that increase or
maximize the ratio of benefits to costs.
Benefit is usually modeled as net energy
gain, i.e., total energy gain less the energetic costs of pursuit, handling, and eating.
Cost is usually modeled as time expended
in pursuit, handling, and eating. Schoener
(1971) explicitly formulated the general
model and applications to animals subject
to different types of constraints on foraging behavior, such as time limitations
imposed by other necessary activities and
variation in relative availability of different
food types.
MacArthur (1972) partitioned foraging
into four decision-requiring phases: where
to search, how to search so as to detect the
presence of an appropriate food item,
whether to pursue the item once detected,
and finally, how to capture and eat it. Subsequently, theoretical advances have incorporated in the models these and other
important aspects of foraging, such as
whether to maximize feeding rate or to
minimize the time spent to gain a fixed
amount of food; whether to continue foraging in the same place or to move, and if
so where to move; foraging from a central
base or home; and the effects of specific
nutrient requirements, proneness to or
aversion of risk, and randomness factors
(Pyke, 1984; Schoener, 1987). Tests confirming predictions of optimal foraging
models have been reported in studies of all
vertebrate classes, active invertebrates such
as arthropods and gastropods (summarized
by Stephens and Krebs, 1987, table 9.1;
see also Hughes, 1986), and such slow-witted forms as clams and echinoderms
(Taghon, 1982).
The most recent synthesis of the entire
field (Stephens and Krebs, 1987) clarifies
the basic components of optimal foraging
models: "decision assumptions" concern
what kinds of choices the forager will analyze; "currency assumptions" concern the
criteria for then evaluating the choices; and
"constraint assumptions" concern environmentally and intrinsically imposed limits on the choices and their "pay-offs" in
currency terms. Stephens and Krebs (1987)
also present models derived from recent
theoretical advances. These are more complex because they increase realism by
incorporating more parameters and fewer
assumptions.
As noted above, empirical and experimental results supporting optimal foraging
models have been widely reported. Stephens and Krebs (1987) and Schoener
(1987) compiled these papers in order to
evaluate the testability and current status
of optimal foraging as an explanatory and
predictive theory. Both concluded that
about 80% of the studies resulted in at least
partial support of the optimal foraging
model being tested. But in an independent
analysis, Gray (1987) reached a very different conclusion, that only about one-third
of the studies actually supported optimal
foraging models. The validity of these tests
has also been questioned on the grounds
that the cases do not fulfill all assumptions
of the model being tested (Pyke, 1984;
Gray, 1987). Other criticisms 1) question
basic assumptions of optimal foraging theory and their testability, 2) state that rejection can always be avoided by suitably modifying the model, and conversely, 3) observe
that by considering only one-way information flow between the organism and its
environment, optimal foraging theory
inadequately addresses the bidirectionality
essential to the hierarchy of control (Fig.
1) and that foraging merits a more inclusive evolutionary approach (Gray, 1987;
Pierce and Ollason, 1987; Schoener, 1987).
While the success of optimal foraging theory is thus debated, it has certainly catalyzed substantial research advances in animal natural history during the past decade.
Pyke (1984), Schoener (1987) and Gray
(1987) all plot the yearly frequency of
papers that develop or test optimal foraging models. These increased exponentially between 1966 and 1981. The regression N = 1.23e025x, where N = number of
papers and x = years after 1965, explains
94% of the variance in Gray's (1987, fig.
1) analysis for this period. However, the
stability in number of papers over 198184 (86, 70, 70, 85, respectively) suggests
an asymptotic curve; the logistic equation,
NATURAL HISTORY AND THE ORGANISM
N = K(l + e-")- 1 with K = 87, r = 0.4,
and t = years after 1968, is a close approximation. In all, Gray (1987) lists 137 theoretical, 276 empirical, and 78 review and
commentary papers published on optimal
foraging through 1984.
Optimal reproductive and life history
strategies
These typically involve the principle of
allocation, e.g., of energy within the organism among physiological and behavioral
requirements. Some decision assumptions
concern the relationships of number and
size of eggs or offspring, and energy committed to reproduction vs. growth, competition, defense, or other activities. Most
are at the organ-system level and below,
but the following involve the whole individual organism: time and energy devoted
to parental care, variable relationships
between mortality and reproductive rate
(models in Alexander, 1982), total reproductive effort and effort per offspring
(Congdon and Gibbons, 1987; Winkler and
Wallin, 1987), and territorial behavior and
territory size (e.g., Carpenter, 1987; Hixon,
1987). The currency in these models is usually fitness or an assumed correlate. Constraints may include those that also affect
foraging, competitors for mates, requirements for defense of territories and young,
and anatomical requirements of other body
functions.
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those involving foraging and reproductive
strategies.
BLOMECHANICAL THEORY IN
NATURAL HISTORY
[It is] important to realize that organisms
do not live in the best of all possible
worlds . . . but in the mundane world of
materials and history. (Futuyma, 1979)
In biomechanics, engineering principles
are applied to organism structure and
functioning and to organism-environment
relationships. One could consider biomechanical theory as a subset of optimality
theory, as implied above in the section on
optimal movements. Decision variables
might be weight and functional capacity,
with the choices minimization and maximization, respectively. Optimality models
have traditionally emphasized the decision
and currency assumptions, although a current trend is toward increased recognition
of constraint assumptions (Stephens and
Krebs, 1987). Biomechanics has traditionally focused primarily on constraints
imposed on an organism's structure and
performance by its design, materials, or
relationship with its solid or fluid environment, and on effects of deviation from
optima. For the purpose of this essay, biomechanics merits a separate heading as a
hypothetico-deductive approach important to natural history.
Assembled as a convergence of heteroOptimal movement
geneous physiologists, physicists, engiConsiderations other than those involved neers, and comparative and functional
with foraging and reproduction also affect morphologists and spearheaded in the U.S.
the decisions of individual animals that by Stephen Wainwright and Steven Vogel
involve movement. Alexander (1982) sum- at Duke University, the field of biomemarizes models of walking and running chanics at the whole organism level has
gaits, flight, and swimming that minimize extended its focus to organisms other than
energy consumption or maximize velocity. vertebrates and has grown rapidly in the
Movements at larger spatial scales include past 15 years. It filled courses at Duke and
dispersal and migration. Models using fit- at Friday Harbor and particularly attracted
ness as currency and that distinguish mor- an array of the brightest young invertephological, ecological and genetic conse- brate zoologists, now dispersed among
quences of the movements of individuals faculties at Berkeley, Chicago, Seattle, and
are currently under active study (Weihs and Stanford. I cite some of their recent conWebb, 1983; several chapters in Swingland tributions below. Since publication of the
and Greenwood, 1983; Bull et al., 1987). seminal work of Wainwright et al. (1976),
They have been less subjected to test than emphasis has shifted somewhat from design
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ALAN J. KOHN
and biomaterials to whole-organism relationships with environment, especially fluid
flow and locomotion. Vogel (1983) provided a major impetus to this most relevant
aspect of biomechanics to natural history;
The ASZ symposium, "Biomechanics"
(Denny, 1984) is an excellent, broad survey, but there has been no up-to-date synthesis of the entire field. I thus indicate a
few specific research directions that link
biomechanics and natural history.
Biomechanics has addressed relationships of individual organisms and their
environment with considerable flexibility.
Animals that move vary widely in size (Fig.
1), velocity, and a correlate of these factors,
the relative importance of viscous and inertial forces. For animals that swim, the
Reynolds number (Re), a measure of this
ratio, varies over some 11 orders of magnitude. Moving animals also vary widely
with regard to acceleration and its relationship to velocity, constancy or steadiness of locomotion, whether the fluid
medium is air or water, and whether movement is entirely within the fluid or on or
in a substratum. A number of studies at the
level of the whole organism are currently
investigating the problems these complex
relationships pose, e.g., unsteady swimming
and the importance of acceleration (Daniel, 1984; Daniel and Webb, 1987), body
and appendage relationships as size, shape
and Re change during development (Williams, 1986; in preparation), burst swimming in zooplankters that lack appendages
(C. Jordan, in preparation). Other problems of current interest include flows
around sessile animals (Koehl, 1984;
LaBarbera, 1984; Vogel, 1984) and the use
of stiff vs.flexiblesupport structures (Vogel,
1984).
RELEVANCE OF NATURAL HISTORY TO
OTHER LEVELS OF BIOLOGY
The questions addressed so far lie
squarely at the level of the whole individual
organism in its environment. The critical
bidirectional controlling interactions
between systems at different levels (Fig. 1;
Grene, 1987) indicate that knowledge of
the organism is necessary to understand
the organization of adjacent levels in the
hierarchy.
Four years ago, an ASZ symposium
forcefully emphasized the important contributions of a "mechanistic" approach to
problems in community ecology. In large
part this term means a focus on the individual organism or natural history as discussed here. Introducing that symposium,
Price (1986) defined the approach as examining "the mechanisms by which processes
operating at the level of individuals and
populations affect properties of communities." Similarly, Schoener (1986) defined
it as "the use of individual-ecological concepts . . . as the basis for constructing a
theoretical framework with which to interpret the phenomena of community ecology."
Relevance to population ecology
Although he focuses primarily on community-level phenomena, Schoener (1986)
also summarizes several series of studies,
most dating from the mid-1970s to mid1980s, that use individual-ecologic attributes as components of population-level
models. These studies analyze patterns of
resource use by individuals, including, for
example, foraging behavior, habitat selection, and functional responses of predators
to varying prey density, and they examine
how these patterns affect population
dynamics, size, age and sex structure, and
reproductive schedules.
Information necessarily passes in both
directions in control hierarchies, as noted
above (Fig. 1). Wethey (1984) gives an
especially clear example of this in his study
of population effects as constraints on the
fecundity of individual barnacles. Individuals of Balanus glandula crowded by conspecific competitors for space do not grow
as large as, and produce fewer eggs than,
uncrowded individuals. Crowded individuals are also less fecund than uncrowded
ones of the same size. In two other species,
the relationship between crowding and
fecundity is reversed. Crowded individuals
in high-density populations benefit reproductively, producing more offspring than
less crowded neighbors of the same size.
NATURAL HISTORY AND THE ORGANISM
Their growth changes from conical to a
more spacious columnar form, biomass
increases, and adjacent individuals share
exoskeletal support structure. In general,
individuals benefit from gregarious living.
These strikingly different responses of
individuals of closely related species to the
same population attribute clearly underscore the importance of basic natural history information for understanding population-level phenomena, as well as the
impact of population density on individuals.
Relevance to community ecology
This was a main thrust of the 1983 ASZ
symposium (Price, 1986). The studies
alluded to in the previous section also link
the individual activities listed above to
community-level phenomena, particularly
species diversity and abundance, coexistence of interspecific competitors of similar and of very different sizes, and interaction of predator and prey dynamics. In
addition, several of the symposium papers
bypass the intermediate population level
and directly relate the same individual
activities to coexistence, community dynamics and stability. These include effects
of foraging, habitat selection, and predator
avoidance behavior on species diversity,
abundance, and differential resource use
patterns (summarized by Schoener, 1986).
1101
fish) overlap each other minimally, the third
member occupies a central position, overlapping both of the others to some extent,
and the overlaps are below the levels
expected to lead to competitive exclusion.
Dayton's careful analysis of individual foraging behavior revealed, however, that the
anemone feeds on scraps from the asteroids' table—prey individuals dislodged by
starfish foraging activity but not eaten fall
into strategically located waiting anemone
mouths. The dietary similarities between
anemone and starfish are due to facilitation, and the competition-based model is
entirely inappropriate to the situation. This
was discovered only through Dayton's
careful attention to individual organismlevel phenomena.
Other areas of biology
In the scope of this essay it has not been
possible to consider in detail other, perhaps no less important aspects of natural
history than those discussed. Natural history provides essential data for both aspects
of the subdiscipline of evolutionary biology, analyses of current evolutionary processes and inferring past processes.
Natural history museums represent a
unique support system, as they preserve
individual organisms as specimens. Their
collections constitute the essential database for documenting organismic variation, distribution, and diversity and their
Dayton's caveat
patterns of temporal change. "Type specMost of the studies that relate individual imens" are among the most important of
behavior to diversity of interspecific com- these objects of natural history. They are
petitors employ the limiting similarity the name bearers to which the original
models of MacArthur and Levins (1967). descriptions of species are irrevocably tied.
But, as Paul Dayton (1973) eloquently The international codes of zoological and
argued, these models may give correct botanical nomenclature now require
answers for the wrong reasons. In one authors of new species to deposit nameof Dayton's examples, diets of two starfish bearing specimens in museums. Although
and a sea anemone overlap in the order early taxonomists were not guided by the
Pisaster-Anthopleura-Pycnopodia. T h e cen- type concept, many specimens that served
trally placed anemone shares the main prey as the basis of their new species descriporganisms of Pisaster, mussels and barna- tions still exist in museums. These specicles, and that of Pycnopodia, a sea urchin. mens—some are now more than two cenDayton found that, as the limiting similar- turies old—provide insights into the
original authors' concepts of nominal
ity model predicts for stable coexistence, species. Appreciating the species that the
the two predators that use the resource original author intended to denote by a
array most differently (here the two star-
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ALAN J. KOHN
specific name is prerequisite to applying
that name to identify an organism under
study.
Type specimens and comparative collections in natural history museums thus provide essential data for classification and
identification, and the consequences of
misidentification may be serious. For
example, the protracted failure to understand the etiology of malaria in Europe is
a particularly well documented effect of
misidentifying organisms belonging to
closely related species (Mayr, 1963). More
broadly, all communication among biologists about most groups of organisms
depends completely on the documentation
this system provides.
Finally, in education, where it is clearly
impossible to teach about all areas or levels
of biology in an introductory course,
emphasis on the whole individual level
organism may be particularly effective
pedagogically. This level is at the students'
own perceptual scale, the biological problems they care most about concern their
own bodies, and the student in the next
seat and the professor at the podium provide convenient study organisms.
DISCUSSION AND CONCLUSIONS
Both historically and at the present time,
natural history is a term applied to an
unusually diverse array of concepts. Some
modern definitions are meaninglessly
broad: "The study of nature, natural
objects and natural phenomena" (Lincoln
and Boxhall, 1987). Marston Bates' (1954)
definition, "the study of. . . organisms,. . .
of life at the level of the individual," is the
most heuristic.
Research efforts focused at the level of
the individual whole organism are important for both intrinsic and extrinsic reasons. In revealing knowledge of the private
perceptual worlds and the real complexity
of behavior of seemingly simple organisms, such research often proves to be a
"magic well." Karl von Frisch is supposed
to have referred to the study of bees in this
way, because the more he drew from his
studies, the more he found that there was
to learn. The same can apply to any taxon.
The general, comparative, and evolu-
tionary approaches to natural history all
have healthy growing points of inquiry. I
have addressed a few aspects that have contributed significantly to advancing both the
theory and data of natural history in the
1980s: determinants of behavior and of
individual organism-environment relationships, how individual behaviors can
affect population dynamics and community
organization, and how mechanical interactions of organisms with their solid and
fluid physical environments relate to their
size, shape, structure and life styles. Prior
American Society of Zoologists symposia
have been important landmarks in all of
these (Howell, 1983; Denny, 1984; Price,
1986) and in other aspects of natural history, such as the relationships of individual
behavior and species recognition (Beecher,
1982) and territoriality (Carpenter, 1987).
All of these examples, and others alluded
to but briefly, emphasize the importance
of natural history information and the
necessity of the level of the whole individual organism for approaching questions
aimed at understanding more general biological phenomena at both higher and
lower levels. Each organism's individuality
and unique genealogy also effectively
express the uniqueness of this level of organization and of biology among the sciences.
ACKNOWLEDGMENTS
The content of this essay developed from
research supported by the National Science Founation, and its preparation was
aided by NSF Grant BSR-8700523.1 thank
Keith Benson, Walter Bock, Tom Daniel,
Chris Jordan, Bob Paine, Louise RussertKraemer and Terri Williams for helpful
discussion and comments on the manuscript.
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