Living and Adapting to Its Own Habitat - Building the Most Complex Structure on Earth - page 229

The energetic cost of processing the stimulus in the brain is not negligible but
neural processing is conserved in the course of evolution because of some benefit
offsetting the cost. The benefit is that the processing figures out ways to adaptively
(in the case of the TDPs, also predictively) respond to the challenges the stressful
stimuli pose to the organism.
Thus, the information for the adaptive responses that lead to phenotypic
(i.e., morphological, physiological, behavioral, and life history) changes in cases of
TDP is generated through processing of stressful environmental stimuli in the brain.
Epigenetics of Behavior and Social Attachment in Animals
Here, behavior is defined as any motor action or sequence of motor actions the
organism performs in response to an external/internal stimulus. Animal behaviors
fall into two groups: innate behaviors, or instincts, and learned behaviors.
Innate behaviors are performed in perfect form from the beginning. An ameba
engulfing debris, a newborn calf suckling its mother's teats, or a plant turning its
flowers or leafs in the direction of the sun, are all examples of innate behaviors that
these organisms perform for the first time without previous experience. Innate behav-
iors rely on the presence of inborn fixed action patterns (FAPs) that are activated in
response to specific stimuli. FAPs result from the activation of specific neural cir-
cuits. Biologists have identified neural circuits for a number of innate behaviors
( Marin-Burgin et al., 2006 ) and the location of some others in the brain ( Balaban,
1997; Long et al., 2001; Teillet et al., 2005 ). How these neural circuits are hardwired
prenatally (i.e., independent of experience) is one of modern biology's enigmas.
Darwin believed innate behaviors evolved in the past from learned behaviors:
Some intelligent actions, after being performed during several generations, become
converted into instincts and are inherited.
Darwin (1874)
Darwin's idea still thrives in modern biology. Some empirical evidence seems to
prove he was right. It is reported that the Australian native black snake Pseudechis
porphyriachus started preying on the cane toad, Bufo marinus , when the toad was
first introduced in the fifth continent. The prey was always lethal to the snake, but
now, 23 generations later, the snake has developed an innate avoidance behavior
toward the toad ( Phillips and Shine, 2006 ). Solitarious desert locusts S. gregaria
(Forskål) prefer to live alone and rest in their niches. They do not fly, except when
disturbed. When they switch to the gregarious phase, they prefer to live in groups
and fly with other locusts. This learned behavior is transmitted to the next generation
as an innate behavior.
The fact that animals perform many behaviors such as chewing, breathing, swal-
lowing, swimming, flying, crawling, and burrowing in the absence of stimuli and
most of them cannot be modified by the sensory input led to the concept of the hard-
wired central pattern generators (CPGs), which are responsible for the above and
other rhythmic behaviors.