Resource Acquisition & Allocation
Energetics
Resource Acquisition & Allocation
Energetics
• A relatively high % of food passes through the
gut unused (80 to 90)
• Food is digested and assimilated and some is
used for respiration and metabolic activity
• The remainder is incorporated into the animal
concerned as secondary productivity (growth
or reproduction)
Resource Acquisition & Allocation
Energetics
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Ingestion = assimilation + egestion
Assimilation = productivity + respiration
Productivity = growth + reproduction
The total amount needed per unit time for
maintenance increases with increasing body
mass
Resource Acquisition & Allocation
Energetics
• Metabolic rates vary on several key aspects
Resource Acquisition & Allocation
Energetics
• Because small organisms have a very high
SA/vol ratio, they have a much higher
metabolic rate (scaled to mass)
Resource Acquisition & Allocation
Energetics
• Because energy is required to maintain a
constant internal body temperature,
homeotherms have considerably higher
metabolic rates, as well as higher energy
needs than poikilotherms (approximating
temperature is that of the environment) of the
same body mass
• Related terms: endotherm & ecotherm
Resource Acquisition & Allocation
Energetics
• The vast majority of animals are ectothermic
and all plants are as well
• Some of the larger poikilotherms are at times
at least partially endothermic
• Behavior allows for
increased efficiencies
Resource Acquisition & Allocation
Energetics
• Because of the
energy requirements
to maintain a
constant body temp
no matter what the
conditions,
endotherms have
considerably higher
metabolic rates
Resource Acquisition & Allocation
Energetics
• There is a distinct lower limit on body size for
endotherms (2-3; hummbird and
shrew…niche?)
• Unique adaptation of hummingbird
Energetics
• Body size, diet and movements are complexy
intertwined with the energetics of metabolism
• Energy requirements do not scale linearly with
body mass, but instead scale as a fractional
component E=km0.67 where k is a taxonspecific constant and m to body mass
Energetics
• Larger animals require larger areas
• Diet also strongly influences the size of a
geographic range (density of prey)
• Hunters and croppers
Energetics
• Larger animals require larger areas
Energetics
• Hunters and croppers on a gradient:
specialists?
Energetics
• Certainly the quality of habitat (productivity)
is going to influence territory size; how?
• How might this influence, if at all, the
evolution of sociality?
Energetics
• Locomotion is another energetic cost, which
varies depending upon the method
• Not surprisingly, terrestrial locomotion is the
most expensive, flying intermediate, and
swimming the least expensive (given certain
constraints)
Energetics
Energetics
• There are a few consistent size-related trends
related to metabolism and energetics
• E.g. mammalian heart is 0.6 % of body mass
• E.g. blood volume, 5.5% of body mass
• Others do vary, but by metabolic rate (lung
volume is directly proportional to MR)
Adaptation and Deterioration of
Environment
• Evolutionary adaptation can be defined as
conformity between the organism and its
environment (genetically, physiologically,
behavioral, and/or developmental flexibility)
• Remember, adaptation does not occur in a
vacuum and there are many constraints and
influences acting simultaneously
Adaptation and Deterioration of
Environment
• Conformity to any given component takes a
certain amount of energy that is then no
longer available for other adaptations
– E.g. reacting to the presence of a predator
reduces foraging efficiency
• Conformity in one area can also restrict
adaptiveness in other areas (consider
physiological trade-offs)
Adaptation and Deterioration of
Environment
• Adaptation to an unpredictable environment
is difficult and perhaps a poor strategy…why?
• One strategy is to go dormant during extreme
periods (whether predictable or not)
Adaptation and Deterioration of
Environment
• A simple, yet elegant, model of adaptation
and undirected environmental deterioration
was developed by Fisher
• He reasoned that no organism is ‘perfectly
adapted’-all fail to conform to something
Adaptation and Deterioration of
Environment
• A 3-dimensional model (competitive,
predatory, and physical environments)
• Small changes could result in a 50:50 chance
of being advantageous
(reducing the distance
between A and B)
Adaptation and Deterioration of
Environment
• The probability of such improvement is
inversely related to the magnitude of the
change
• Individuals will always
overshoot points of
closer adaptation
• Think microscope
and adjusting it
Adaptation and Deterioration of
Environment
• So which is better, a specialist or generalist?
• Environments deteriorate…
Adaptation and Deterioration of
Environment
• Water economy in desert organisms
• Many ways to go about it, but losses must be
replaced by gains
• Consider desert plants; what kind of roots to
grow?
Adaptation and Deterioration of
Environment
• Consider the
creosote bush
(Larrea), it has both
a surface root
system and a deep
tap root
• Many Cacti have an
extensive, but
shallow root system
Adaptation and Deterioration of
Environment
• Other desert plant are mesophytic, only
growing during periods of abundant water
• During droughts, drop leaves and go dormant
• Less dramatic, some plants
wilt during the day…why?
Adaptation and Deterioration of
Environment
• Camels do not rely on water storage, but can
withstand losing as much as ¼ of body mass
(primarily as water loss)
• They also allow themselves to overheat..why?
• Extreme electrolyte concentrations
• Behavior can be important
Adaptation and Deterioration of
Environment
• Many other materials can be limiting as well
(e.g. Ca, Cl, Mg, N, Na and K)
• Na, K, and Cl are all required in neural
mechanisms
• Herbivores generally have problems with Na;
why?
• Could plants utilize this problem to their
advantage?
Adaptation and Deterioration of
Environment
• Guinea pigs and the Indian fruit-eating bat
cannot produce ascorbic acid. Who else
cannot?
• Why should natural selection favor the loss of
the ability to make a vital mineral?
Adaptive Suites
• Any given organism possesses a unique
coadapted complex of physiological,
behavorial, and ecological traits whose
function it is to compliment one another and
enhance that organism’s survival and
reproductive success
• This has been termed ‘optimal design’
Adaptive Suites
• Consider the desert horned lizard
• Various features of its anatomy, behavior, diet,
temporal pattern of activity, thermoregulation
and reproductive tactics are interwoven and
make this one neat lizard!!
Adaptive Suites
13%
Adaptive Suites
• The weasel is another
great example of a
suite of adaptations
coexisting
• Body shape requires
more energy (but must
also have some
benefits)
• Sexual size dimorphism
Adaptive Suites
• Design constraints
• Natural selection has come
up with lots of interesting
adaptations
• E.g. photosynthesis,
immune response, vision,
flight, echolocation,
navigation
Adaptive Suites
• Design constraints
• Natural selection has come
up with lots of interesting
designs, although none
perfect
• E.g. most efficient
locomotion?
Adaptive Suites
• Upper physiologic limit of 40oC; why?
• Consider the evolution of homeothermy
– Homeothermy is a by-product of advantages
gained from maintaining maximum body
temperatures in the face of such an innate
physiological ceiling
• Remember, all homeotherms are NOT
endotherms (strong behavioral selection)
Adaptive Suites
• Thermoregulation in lizards is
actually very complex
• Notice all the different
times/places lizards are active
(morning, day, night)
• Vary in location (arboreal,
subterranean, ground)
• Body temps vary (25-38oC)
Adaptive Suites
• Interspecific variation
• Body temperature range
– Arboreal vs. ground
– Favors precise thermoregulation
• Ground dwellers have it tough
– Lack of basking sites (dawn/dusk)
Adaptive Suites
• Consider an analysis
of C/B of lizard
thermoregulatory
strategies
• Slope (between body
temp vs. ambient
temp)
• b=1 is true
poikiolothermy, 0 is
endothermy
Adaptive Suites
• Notice the intercepts
(38.8oC)
approximates the
point of intersection
of all regression
lines, perhaps
representing an
innate design
constraint
Adaptive Suites
• Birds descended from another reptilian stock,
the archosaurs (crocodilians)
• They have a higher body temperatures than
mammals
• Could you make predictions concerning a
comparable study using crocodiles?
• How about insects?
Adaptive Suites
Adaptive Suites
Adaptive Suites
Adaptive Suites
Adaptive Suites