183
D. Kar, Wetlands and Lakes of the World,
DOI 10.1007/978-81-322-1023-8_10, © Springer India 2013
It may be assumed that there are at least as many
strategies for survival as there are species, perhaps, more. It is because particular species may
adopt different strategies in different places or at
different times. However, emphasis has been laid
on the planktonic and benthic organisms because
they refl ect the opportunities and constraints
associated with life in water very clearly.
Virtually, all attributes of an organism, e.g.
body form, colour, behaviour, diet, reproductive
method and habitat requirement, are of selective
importance. Strategies for survival encompass all
these multitudinous facets.
The phrase ‘strategies for survival’ is used
generally for literary expedience. Certainly, it
does not imply any planning for the future on the
part of an organism. Past experience of selection
pressures is generally refl ected by the so-called
adaptations of organisms. The products of past
selection pressures are likely to do well in the
present or near future. It is because there is often
a very good correlation between the past and
future events or environmental conditions.
Notwithstanding the above, a common theme of
life history strategies is the trade-off between
investment of time and energy on confl icting needs.
Each case is a compromise and an optimal solution
for simultaneous problems. Properties, e.g. competitive ability, predator defence and productivity,
tend to detract from each other mainly because of
limited time or energy available to an organism.
In this regard, some of the stimulating references
within the general area of evolutionary ecology
include Harpes ( 1978 ), Krebs and Davies ( 1978 ),
Maynard Smith ( 1978 ) and Pianka ( 1978 ).
10.1 Feeding
Attempt to differentiate between biota of land
and water reveals generally two outstanding
distinctions. These are as follows:
(a) Many organisms live permanently in the
water column, while virtually no organism
lives permanently suspended in air.
(b) Many aquatic organisms living fi xed to the
substratum are animals. But, most sedentary
organisms on land are plants.
The fi rst distinction is due to the high density of
water relative to that of air. The second difference
is partly due to the higher density of water and the
rapid attenuation of light passing through water.
10.2 Clones and Modular Colonies
It is said that asexually produced offspring remain
attached to the parent and form a colony of modular construction. Alternatively, they may also
detach from the parent to form a clone of free individual. However, both these depend on the lifestyle of the organism. Colonies of modular
construction, e.g. colonial hydroids, bryozoans,
tunicates, macroalgae and higher plants, are able
to compete effectively for space, suspended food
particles or light by lateral sheet-like growth over
10
Strategies for Survival of Aquatic
Organisms
D. Kar, Wetlands and Lakes of the World,
DOI 10.1007/978-81-322-1023-8_10, © Springer India 2013
It may be assumed that there are at least as many
strategies for survival as there are species, perhaps, more. It is because particular species may
adopt different strategies in different places or at
different times. However, emphasis has been laid
on the planktonic and benthic organisms because
they refl ect the opportunities and constraints
associated with life in water very clearly.
Virtually, all attributes of an organism, e.g.
body form, colour, behaviour, diet, reproductive
method and habitat requirement, are of selective
importance. Strategies for survival encompass all
these multitudinous facets.
The phrase ‘strategies for survival’ is used
generally for literary expedience. Certainly, it
does not imply any planning for the future on the
part of an organism. Past experience of selection
pressures is generally refl ected by the so-called
adaptations of organisms. The products of past
selection pressures are likely to do well in the
present or near future. It is because there is often
a very good correlation between the past and
future events or environmental conditions.
Notwithstanding the above, a common theme of
life history strategies is the trade-off between
investment of time and energy on confl icting needs.
Each case is a compromise and an optimal solution
for simultaneous problems. Properties, e.g. competitive ability, predator defence and productivity,
tend to detract from each other mainly because of
limited time or energy available to an organism.
In this regard, some of the stimulating references
within the general area of evolutionary ecology
include Harpes ( 1978 ), Krebs and Davies ( 1978 ),
Maynard Smith ( 1978 ) and Pianka ( 1978 ).
10.1 Feeding
Attempt to differentiate between biota of land
and water reveals generally two outstanding
distinctions. These are as follows:
(a) Many organisms live permanently in the
water column, while virtually no organism
lives permanently suspended in air.
(b) Many aquatic organisms living fi xed to the
substratum are animals. But, most sedentary
organisms on land are plants.
The fi rst distinction is due to the high density of
water relative to that of air. The second difference
is partly due to the higher density of water and the
rapid attenuation of light passing through water.
10.2 Clones and Modular Colonies
It is said that asexually produced offspring remain
attached to the parent and form a colony of modular construction. Alternatively, they may also
detach from the parent to form a clone of free individual. However, both these depend on the lifestyle of the organism. Colonies of modular
construction, e.g. colonial hydroids, bryozoans,
tunicates, macroalgae and higher plants, are able
to compete effectively for space, suspended food
particles or light by lateral sheet-like growth over
10
Strategies for Survival of Aquatic
Organisms