topic 7 - energy budgets Flashcards
what is the difference between organisms in energy demands
differ in the relative amounts they spend on each part of their life history
what do energy budgets depend on
size
environment
thermoregulation
what is the difference in energy demand between larger and smaller animals
larger = more energy required but less per unit body mass
smaller = less total energy required but more per unit body mass
what is the energy allocated to homeostasis used for
wear and tear
metabolism
survival (big portion)
what is the energy for thermoregulation used for
keeping body temp within limits
(not present in ectotherms)
how does size impact energy demand
the way they move, how often they eat, and what they eat
what is scaling
how size/mass affect anat/phys/bio processes
what happens when you scale up a dimension
means more SA and even more volume
more SA = more membrane / skin
more volume = more mass
what is the difference in SA V ratio in different sized organisms
larger = smaller SA V ratios
(lots of volume and very low SA to interact with the environment proportionally)
- evolved ways to increase SA to exchange matter and energy with their environment (lungs, kidneys, blood vessels, intestines, etc)
how does the scaling of SA work
SA scales with mass - because mass and V are related
what do logarithmic axes mean
shows a predictable relationship
what are the implications of body size scaling
organisms need to obtain resources and excrete waste to support their mass (volume)
organisms exchange matter and generate energy across their membranes (SA)
what is the disadvantage for large organisms with their SA V ratio
reduced efficiency (lots of biomass to “service” but relatively low SA to do it with)
diffusion distance (large distance to flow inside to out)
specialised systems (need to divert energy to building and maintaining systems to increase SA)
what are the advantages for large organisms with their SA V ratio
heat retention (heat produced by large volume but lost through small SA)
water conservation
structural strength
what is the formula for allometry
y = aX^b
mass (X) effect on any given biological variable is given by this power function
a = value of Y per unit mass
b = scaling component
what is the meaning of b (scaling component)
b = 1 - isometry (flat line)
b = 0 - biological variable is independent of body mass
0<b<1 = increase and then plateau
b>1 = exponential increase
b<0 = exponential decrease
what is isometry
variable scaling at the same rate as body size
ex: heart mass scales at the same rate as body mass for marsupials
what is the benefit of log transformations
used to understand power relationships (esp in allometry)
what is positive/hyper allometry
slope > 1 on log transformed graph
as one variable increases, the other increases at a faster rate
ex: as body size increases, the claw size grows at a faster rate
what is negative/hypo allometry
slope < 1 on log transformed graph
as one variable increases, the other increases at a slower rate
ex: as body size increases, the brain grows at a slower rate
what are the types of energy usage
assimilation = what gets used by the organism
= RMR + activity + production
= available energy
RMR = energy used at rest
activity = behaviour, reproduction, thermoregulation
production = stored by the organism (ex: from growth)
excretion = what is lost by the organisms to the environment
how does body size affect energy in larger animals
need more food
- greater energy per unit time
eat more food
- eat less relative to body size
take in more air and pump more blood with each breath / heartbeat
- slower breathing and HR
how to minimise energy excretion (maximise assimilation)
chewing, selecting palatable food, length of gut (hyperallometric), food retention time (hypoallometric)
what is energy RMR
rate of energy consumption per unit time at rest with routine activities
rate at which organisms converts chemical energy to heat and external work
calories/t or J/t
helps determine how much food an animal needs
what is BMR (basal metabolic rate)
metabolism at complete rest (lowest possible)
measured while fasting in vertebrates
done on endotherms
what are the considerations with BMR
standard measure of metabolic rate
measure on endotherm when animal is in a thermoneutral zone, fasting, and resting
what is SMR (standard metabolic rate)
metabolic rate measured at a specified temp (ectotherms)
- don’t regulate internally, so need to specify temp
- still done while fasting and resting
what is FMR (field metabolic rate)
metabolic rate measured in wild animals
might not be accurate because not lab controlled
what is direct calorimetry
measures the rate at which heat leaves an animals body
expensive and cumbersome
what is indirect calorimetry
respirometry - measuring an animals state of resp gas exchange with environment
(O2 consumed or CO2 produced as proxy for metabolism)
material balance method - measuring the chemical energy content of the organic matter that enters and leaves the body
(uncommon)
how does RMR scale with body size
bigger = more RMR
negative allometry
body mass and RMR have the same slopes across organisms
y = aX^0.75
- metabolic rate increase with mass raised to the 3/4 power
how to calculate mass specific metabolic rate
metabolic rate per unit body mass
whole organism rate/mass
Y - aX(b-1)
(b-1) = always negative for mass specific rate
decreases with increases body weight
- holds for any biological variable when you make it mass specific
what is the effect of activity on energy
increases heat generated
includes most forms of mvmt above resting state
activity increase may offset the thermoregulation costs of a dormant (resting) organism
what is the effect of growth and reproduction on energy
production represents both growth and reproduction
balanced energy budget - should = 0
more than enough energy consumed = positive and mass will increase
not enough energy consumed = negative and mass decreases
