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R AND K SELECTED SPECIES powerpoint presentation
1. R- AND K -SELECTED
SPECIES-power point
presentation.
2. LIFE HISTORY STATEGIES
๏ Life history strategy is correlated with many aspects of an organisms
reproductive strategy and life history , as well as with demographic
variables such as
-generation time
-life span
-population parameters such as population density and population
dynamics.
๏ Invoked to predict the relative influences of density dependant versus
density independent ecological influences on life stages and age classes.
๏ The most notable example of life history theory is that of r and k
selection ( Mac Arthur and Wilson ,1967) based on their work on island
biogeography.
3. POPULATION GROWTH
๏ The variable r and k in r/k selection
comes from the logistic equation for
population growth.i.e
dN/dt = rN ( 1 โ N/K )
๏ r represents the intrinsic rate of natural
increase of a species.
Mathematically,
r = (birth rate + immigration rate )
โ (death rate + emigration rate)
๏ K refers to the carrying capacity of the environment ,that is the
maximum density at which a population is able to exist in a given
environment.
14. Conclusion
๏ The distinguishing feature of the r- and k- selection paradigm was the
focus on density-dependent selection as the important agent of
selection on organismsโ life histories.
๏ The paradigm was challenged as it became clear that other factors, such
as age-specific mortality, could provide a more mechanistic causative
link between an environment and an optimal life history.(Streams 1976,
1977).
๏ The r- and k- selection paradigm was replaced by a new paradigm that
focussed on age โspecific mortality (Streams, 1976; Charlesworth,
1980). This new life-history paradigm has matured into one that uses
age-structured models as a framework to incorporate many of the
themes important to the r-k paradigm.
15. References
๏ Winemuller, KO. 2005. LIFE HISTORY STRATEGIES, POPULATION REGULATION,
AND IMPLICATIONS FOR FISHERIES MANAGEMENT. Can.J.Fish.Aquat.Sci.62:872-
885.
๏ Roff, D.A.1992. THE EVOLUTION OF LIFE HISTORIES: THEORY AND ANALYSIS.
Chapman and Hall, New York.
๏ Stearns, S.C.1992. THE EVOLUTION OF LIFE HISTORIES. Oxford University Press,
Oxford.
๏ King, Charles E. and watt W. Anderson, 1971. AGE-SPECIFIC SELECTION.2. The
interaction between r- and k- during population growth. Am. Naturalist 105:137-156.
๏ MacArthur, Robert H. and Edward O.Wilson, 1967. THE THEORY OF ISLAND
BIOGEOGRAPHY. Princeton University Press, Princeton, New Jearsey.
๏ Margalef, Ramon, 1958. Mode of evolution of species in relation to their places in
ecological succession. 15th Int. cong. Zool. Proc. 10:787-789.
๏ Charlesworth and Michael R.Rose, 1980 ; EVOLUTIONARY BIOLOGY OF AGING
๏ King. J.R. and G.A. McFarlane, 2003. Marine fish life history strategies: applications to
fishery management. Fish. Manage. Ecol. 10:249-264.