Homeostasis

Regulating vs Conforming

Difference between regulating and conforming

Why is regulation more energy expensive than conforming?

Adaptation needs to outweigh the needs of the body more than the benefits of the body

Balances

The natural environment is a system of balances Law of thermodynamics

Input and output should be equal When will there be an imbalance?

Thermoregulation

Temperature affects a lot of things- Proteins- Membranes- What else?

Four physical processes of heat gain and loss

ConductionConvectionRadiation Evaporation

What is a wind chill effect?

Endothermy vs Ectothermy

Define endotherm/ ectothermTrue or false: ectotherms are always cold-

blooded.

Advantages of endothermy

Longer vigorous activities than ectotherms Sustained activity is only possible in

endotherms Thermal problems living in a terrestrial

environment is resolved through endothermy; e.g. endotherms can live in below-freezing production- temperature that deactivate the metabolism of ectotherms

Disadvantage of endothermy

Thermoregulators invest more energy in their activity than conformers, thus, increasing the energy intake of regulators.

Question: why is ectothermy a good strategy in living in a new environment?

Adaptation of animals that thermoregulate

• Adjusting the rate of heat exchange between the animal and its surroundings

• e.g. insulation such as feathers, fat• changes in the circulatory system-

vasodilation/vasoconstriction• countercurrent heat exchange- arteries are in

opposite direction that of veins in the extremities; heat exchange is determined by physiology or environment

Cooling through evaporative heat lossBehavioural response- posture or movement

(migration/hibernation/estivation/winter sleep)

Changing the rate of metabolic heat- applies only to endotherms

Mechanisms of temperature control

Mammals/ birds Constant heat loss Constant heat production Nonshivering thermogenesis vs shivering

thermogenesis

Nonshivering thermogenesis (NST)

Hormones- inc metabolic activity of mitochondria rather than production of ATP

Brown fat InsulationBlubber

Panting and evaporative cooling

Increase rate of heat exchange

How does fur/hair help in insulation?

Amphibians and Birds

Movement is key to heat productionProduction of mucus to counter evaporative

coolingReptiles have scales that inc skin’s SAVasoconstriction in extremities of marine

iguana

FIshes

Mostly are conformersEndothermic fishes use countercurrent heat

exchange systemPresence of special heat generating organs

Invertebrates

Aquatic invertebrates- mainly thermoconformers

Terrestrial invertebrates- same as vertebrate ectotherms

Flying insects- smallest endotherms

Flying insects

Generate heat through flight musclesCountercurrent exchange mechanisms

Shutdown mechanisms during hot weather

Uses shivering in incubationHuddling Evaporative coolingfanning

Thermostat

Controls temperatureWarm receptors- indicate inc in tempCold receptors- indicate dec in tempWhat kind of mechanisms will each receptor

activate?

Below normal range?Above normal range?

Acclimation vs acclimatization

Acclimation- laboratoryAcclimatization- natural environment

Antifreeze- used by ectotherms in sub-zero environment

Proteins- e.g. Heat shock proteins

Torpor

Physiological state of low activity and low metabolism

Hibernation vs winter sleepEstivationDaily torpor

Osmoregulation

Functions in maintaining the composition of the cell’s cytoplasm

Mostly done indirectlyOpen circulatory- uses hemolymphClose circulatory- use interstitial fluidKidneys are specialized organs in maintaining

the composition of the body’s fluid composition

Transport epithelia

e.g. transport epithelium face the outside environment to release unwanted solutes but have tight junction in between cells to inhibit back flow; functions like the Casparian strip of plants

Ammonia

Most common in aquatic animalsCan easily pass through membranes via diffusionInvertebrates release ammonia all throughout the

bodyFish release ammonia in the form of ammonium

ions through the gills (kidneys excrete only minimal amount)

Freshwater fishes excrete NH4 ions but also take in Na ions through the gill epithelium to have a higher concentration of Na ions compared to the environment

Urea

less toxic compared to ammoniaNeed less water in eliminatingUsed by mammals, adult amphibians, marine

fishes and turtlesAmmonia+CO2Transported via the circulatory system and

filtered in the kidneys

Can be transported in high concentration due to low toxicity

Uses more energyAnimal adaptation: amphibians in water

excrete ammonia but excrete urea in land, what is the advantage of this lifestyle?

Uric Acid

relatively nontoxic nitrogenous wasteInsoluble in water and excreted as semisolid

pasteAdvantage: low water lossDisadvantage: highly expensive Present in land snails, insects, birds, reptiles

Osmoconformers vs osmoregulators

Osmoconformers- animals that have the same concentration of body fluid and of the external environment; live in relatively stable environment

Osmoregulators- maintains the concentration of body fluid; body fluid is not isoosmotic with that of the environment

Stenohaline- animals that cannot tolerate broad change in solute concentration

Euryhaline- animals that can tolerate substantial change in external osmolarity, e.g. salmon