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and physiology and more to do with how the same or very similar genes
are controlled via the epigenetic template (Maggio et al. 2006; Yaish et al.
2011; Gonzalez et al. 2013).
B. Dormancy: The Original Developmental Environmental
Defense Program
Among the many mysteries of biology, the explosion of speciation of
complex multicellular metazoans at the beginning of the Cambrian has
drawn intense interest. A strong argument can be made that multi-
cellularity and complexity do not offer overall competitive advantages
since single cell and simpler multicellular organisms out number and
even exceed the biomass of complex multicellular organisms by far. The
most likely advantage of initial cellular differentiation was to allow
encroachment into a broader range of environments. The likely origin of
this strategy was a combination of specialized cells, one highly tolerant
to environmental extremes and the other capable of rapid proliferation
in more optimal environments (Marshall 2006). Eventually many ver-
sions of such specialized cells would evolve to allow habitation of
various environments, but probably all would include a form of dor-
mancy as evidenced now by the taxonomically ubiquitous spore (Oliver
et al. 2005; Lopez et al. 2009). These special defensive cell types would
also develop to deal with organism versus organism challenges and this
may help explain the close relatedness between genes involved in both
development and energy management for growth and biotic defense
(Narsimhan et al. 2009).
In the evolution of plants, there has been a consistent decrease in the
complexity of the gametophyte to where it has become a diminutive
structure that is parasitic on the sporophyte (Gilbert 2003), probably as a
result of heterochronic adjustment (Cronk 2001). After the evolution of
sexual reproduction, recombination, and eventually the gene silencing
system, the importance of an adult haploid version of a species for
quality checking the genome would diminish because functional hap-
loids can occur at recombined or silenced alleles (Walbot and Evans
2003). However, the need to alternate phenotypes matching seasonal
environmental change would persist. One may consider that
flowering
plants (most of our crops) accomplish intragenerational alternation of
extremely different epigenetic states that greatly affect their environ-
mental
fitness. They remain in a stress sensitive form for most of the life
of the sporophyte and also after meiosis and subsequent formation of the
gametophytes (embryo sac and pollen). Then, after fertilization they take
on an extremely stress tolerant phenotypic version of the sporophyte, a
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