Regulation and homeostasis are important for animals to maintain stable internal conditions. There are two main strategies - regulation and conformity. Regulators actively modify their internal environment through processes like thermoregulation and osmoregulation, while conformers passively change with their external environment. Examples of regulators include mammals and salmon, while ectotherms are usually conformers. Homeostasis requires energy to maintain balance between energy intake and output. When regulating temperature or water balance, animals use various physiological and behavioral adaptations depending on their environment.

1. Homeostasis, osmoregulation and excretion wind-chill factor- wind increases the loss of heat by increasing rate of
transfer in a cold environment
Regulating and conforming
radiation – emission of electromagnetic waves by all objects warmer than
Regulators- animals that modify their internal environment through absolute zero
homeostasis
e.g. ectothern basking in the heat of the sun
e.g. thermoregulators- mammals
evaporation- removal of heat from the surface o f a liquid that is losing its
osmoregulator- salmon molecules as gas
Conformers- changes internal environment through changes in the external e.g. cooling effect of evaporation of sweat
environment
- Live in more stable environment
Ectotherms have body temperatures close to environmental temperature;
e.g. ectotherms. Osmoconformers endotherms can use metabolic heat to keep body temperature warmer than
their surroundings
There are no perfect conformers and regulators, only a mixed of both in the
natural environment The four processes that transfer heat are used by animals in combination
Regulation is more energy exhausting than conforming Ectothern- low metabolic rate; heat produced is too low to affect body temp,
body temp is dictated by the environment
Adaptation is needed to outweigh the needs of the body rather than the
benefits of homeostasis Endotherm- high metabolic rate increases its body temperature higher than
that of the external environment
Advantages of endothermy
Homeostasis balances the loss and gain of energy
High aerobic metabolism
Input in energy will only be higher than output if animal is reproducing or
growing Longer vigorous activities than ectotherms
Imbalance can cause diseases or death if severe Sustained activity is only possible in endotherms
Homeostasis can be viewed as a budget in energy consuming energy Thermal problems living in a terrestrial environment is resolved
through endothermy; e.g. endotherms can live in below-freezing production-
Energy consumption depends on the availability of resources, e.g. temperature that deactivate the metabolism of ectotherms
reproduction may be cancelled for the next season of breeding if not enough
energy will support its maintenance Disadvantage of endothermy
Thermoregulators invest more energy in their activity than conformers, thus,
increasing the energy intake of regulators.
Regulation of body temperature
Question: whys is ectothermy a good strategy in living in a new
Temperature affects different body mechanisms environment?
e.g. proteins are affected by heat- enzymes function at a faster rate if the Thermoregulation involves physiological and behavioural adjustments
temperature of the environment is increased, but will denature if the
temperature is too high Adaptation of animals that thermoregulate:
membranes are also affected by temperature changes, it being composed of 1. Adjusting the rate of heat exchange between the animal and its
lipids and proteins that greatly depend on temperature for its function surroundings
four physical processes account for het gain or loss e.g. insulation such as feathers, fat
conduction- direct transfer of heat through direct contact of molecules changes in the circulatory system- vasodilation/vasoconstriction
e.g. an ectotherm lying on a rock to increase its internal countercurrent heat exchange- arteries are in opposite direction
environment that of veins in the extremities; heat exchange is determined by
physiology or environment
convection- transfer of heat through the movement of air or water
2. Cooling through evaporative heat loss
e.g. movement of blood from warmer area of the body to the colder
extremities 3. Behavioural response- posture or movement
(migration/hibernation/estivation/winter sleep)

2. 4. Changing the rate of metabolic heat- applies only to endotherms Reptiles like amphibians keep their body temperature by moving; scales on
their body can increase the surface area that comes in contact with the heat
of the sun
Physiological adaptation is also used by reptiles in restoring body
temperature; marine iguana for example, increase vasoconstriction in their
Most animals are ectothermic but endothermy is widespred skin to move blood towards the core of the body to decrease heat loss in the
cold sea. Also, temporary endothermy is present in large reptiles such as the
Mechanisms of thermoregulation phyton that shivers to incubate its eggs
Mammals and birds Fishes
Mammals- 36-38C Most fishes are conformers when it comes to maintaining its body
temperature
Birds- 39-42C
Powerful swimmers such as the tuna, swordfish and great white shark are
Constant heat loss is present endotherms- blood is conveyed to deep muscles where the vessels are
arranged in a countercurrent heat exchange
Adaptation: high metabolic rate that constantly produce heat that replaces
what is lost; e.g. muscle activity or shivering Question: why do you think powerful swimmers such as the swordfish are
endotherms rather ectotherm?
Nonshivering thermogenesis (NST)
Special heat-generating organs are also present in some species of fish; heat
Hormones can also increase the metabolic activity of the mitochondria may increase the effectiveness of these organs
instead of ATP
Invertebrates
Brown fat- present in the thorax; rapidly releases heat
Aquatic invertebrates- mainly thermoconformer
Insulation – reduces heat flow, thus, heat loss
Terrestrial invertebrate- same as vertebrate ectotherm
- Reduces energy of heat production
Flying insects- smallest endotherms
Question: Why trapping air in raised fur or hair decreases heat loss?
- Generate heat through action of flight muscle
Blubber helps decrease heat loss in marine mammals
- Chemical reactions, e.g. cellular respiration, is speed up
Heat loss is higher in aquatic environment than in a terrestrial environment
- Presence of countercurrent heat exchanger
Hair loses its insulating property in an aquatic environment but marine
mammals have blubber that are very effective insulating the bodies - Insects can overheat during hot weather, presence shut
down mechanism of the countercurrent heat exchanger
Thermoregulation of mammals and birds: metabolic heat production,
insulation and vascular adjustments - Bumblebee queen- use shivering to incubate eggs
Panting- mechanism that enhances evaporative cooling - Huddling- used by bumblebee colony to increase
temperature in the hive
- Increases evaporation through increased contact between
the air and the blood vessels - Huddling uses up energy, honey is used as fuel
Evaporative cooling is also enhanced by action of the sweat glands through - Uses also evaporative cooling (water) and convection
the nervous system, spreading of saliva on body surfaces, use of saliva and (fanning)
urine
Feedback mechanism in thermoregulation
Thermoregulation is controlled by the nervous system
Amphibians and Reptiles
Hypothalamus is the part of the brain that controls the thermostat of the
Amphibians lose body heat rapidly when exposed to air due to evaporation body
of moist body surfaces
Thermostat- a device used to control the changes in temperature over a set
Body temperature is maintained through movement (warm to cold or vice of range (body temperature is controlled through heat gain or loss)
versa) or increase in the production of mucus to decrease the effect of
evaporative cooling Nerve cells for temperature- found in the skin, hypothalamus, other body
organs
Warm receptors- indicate increase in temperature

3. Cold receptors- indicate decrease in temperature Winter sleep- bigger animals do not go hibernation but rather winter sleep;
body temperature is decreased but unlike that of hibernation body
Below normal range- heat-loss mechanism is shut down temperature only drops a few degrees Celsius
- Heat-saving mechanism is turned on Hibernation is not present in large animals because to arouse a big animal
like a bear during hibernation it will need large amount of energy to do it.
- Vasoconstriction of peripheral BV Also, large animals have less need to save metabolic fuels due to low normal
basal metabolic rate: energy store ratio
- Erection of fur or hair
Estivation – summer torpor; slow metabolism and inactivity, e.g. lungfish and
- Switching on of shivering and non-shivering mechanisms some African frogs
Above normal range- heat-retention mechanism is shut down Daily torpor- present in bats and other small animals; these animals undergo
sleep to inactivate or slows down metabolism during resting
- Vasodilation, evaporative cooling and panting is used
Sleep in humans may be an evolutionary adaptation of daily torpor
Water balance and waste disposal
Both action responds through negative feedback mechanism
Osmoregulation- management of the body’s water concentration and solute
Question: How is negative feedback mechanism employed in the cooling and
composition
heating of the body?
- Functions in maintaining the composition of the cell’s
Adjustment to Changing Temperature
cytoplasm
Acclimatization- broad range of changes brought about by long exposure to
- Mostly done indirectly
environmental conditions (natural environment)
- Open circulatory- uses hemolymph
Acclimation- a specific change brought about by long exposure to changes in
the environment (laboratory) - Close circulatory- use interstitials fluid
Acclimatization in endotherms - Kidneys are specialized organs in maintain the composition
of the body’s fluid composition
Growing of thick fur during winter and shedding it during summer;
change in heat production in different seasons
Water balance and waste disposal depend on transport epithelia
Acclimatization in ectotherms
Transport epithelium- has a characteristic feature that regulates the
Compensating in the changes in body temperature, e.g. during movements of particular solutes in specific direction
summer bullhead catfish can survive up to 36C but cannot function in cold
water conversely during winter they can tolerate cold water but dies if the e.g. transport epithelium face the outside environment to release
temperature is below 28C unwanted solutes but have tight junction in between cells to inhibit back
flow; functions like the Casparian strip of plants
Also, acclimatization in ectotherms involves changes at the
cellular level. Increase in the production of a specific enzyme can be used to An animal’s nitrogenous waste wastes are correlated with its phylogeny and
speed up reaction (low temperature decrease enzyme action) or production habitat
of new enzyme that has a lower temperature optima. Lastly, proportion of
saturated and unsaturated lipids in the membrane is changed to retain the Metabolic wastes are dissolved first in water before elimination (except CO2
fluidity of the membrane. in air-breathing animals)
Antifreeze- used by ectotherms in sub-zero environment Removal of nitrogenous waste depends on metabolism and diet of animals
Cells also produce stress-induced proteins stimulated by different factors Endotherms eat more food thus excrete more wastes
such as heat, change in pH, etc
Predators release more nitrogenous wastes compared to animals that eat
Heat-shock proteins- produced by cells to combat sudden change mainly carbohydrates or fats
in temperature to inhibit protein denaturation in the cell
Ammonia- very toxic; can be tolerated at very low concentration
- Most common in aquatic animals
Torpor conserves energy during environmental extremes
- Can easily pass through membranes via diffusion
Torpor- physiological state of low activity and low metabolism
- Invertebrates release ammonia all throughout the body
Hibernation- long-term torpor as an adaptation to winter cold and food
scarcity (present only in small animals)

4. - Fish release ammonia in the form of ammonium ions Hypoosmotic- low solute concentration
through the gills (kidneys excrete only minimal amount)
Water moves from hypoosmotic to hyperosmotic solution
- Freshwater fishes excrete NH4 ions but also take in Na ions
through the gill epithelium to have a higher concentration of Osmoregulators and osmoconformers
Na ions compared to the environment
Osmoconformers- animals that have the same concentration of body fluid
Question: Why do freshwater fishes need to take in Na ions? and of the external environment; live in relatively stable environment
Urea- less toxic compared to ammonia Osmoregulators- maintains the concentration of body fluid; body fluid is not
isoosmotic with that of the environment
- Need less water in eliminating
- Discharge water if it lives in a hypoosmotic environment
- Used by mammals, adult amphibians, marine fishes and
turtles - Take in water if it lives in a hyperosmotic environment
- Ammonia+CO2 - Requires energy to maintain osmotic gradient
- Transported via the circulatory system and filtered in the - Uses active transport mechanisms in moving solutes
kidneys
Stenohaline- animals that cannot tolerate broad change in solute
- Can be transported in high concentration due to low toxicity concentration
- Uses more energy Euryhaline- animals that can tolerate substantial change in external
osmolarity, e.g. salmon
- Animal adaptation: amphibians in water excrete ammonia
but excrete urea in land, what is the advantage of this Maintaining water balance in the sea
lifestyle?
Most invertebrates are osmoconformers and some vertebrates, e.g. hagfish
How is urea advantageous against ammonia in living on a terrestrial
environment? These animals are isoosmotic with the environment but composition of the
body fluid is different from that of the environment
Uric Acid- relatively nontoxic nitrogenous waste
Most marine vertebrates are osmoregulators except the hagfish
- Insoluble in water and excreted as semisolid paste
- These animals lose water very fast
- Advantage: low water loss
- Eat food high in water and take in large amount of salt water
- Disadvantage: highly expensive
- Salt is actively transported in the gills
- Present in land snails, insects, birds, reptiles
- Little urine is produced
Mode of reproduction also determines the kind of nitrogenous waste used
Cartilaginous fishes on the other hand use another strategy regulating their
internal environment
Non-shelled embryo uses urea because it can diffuse out of the
shell-less egg of an amphibian or through the circulatory system of the
- Salt is taken in via food and through diffusion to the body
mother in mammals
- Some of the salt load is excreted via the kidneys and a
But, urea can accumulate in to a harmful concentration if it is not
special organ called rectal gland or it is lost via fecal
eliminated. Shelled embryo like that of birds uses uric acid because even if it
elimination
accumulate in the egg it will precipitate out
- Water loss is prevented by increasing the amount of urea
Evolutionary lineage also determines the kind of nitrogenous waste.
inside the body and the use of another organic solute called
Terrestrial turtles use uric acid while sea turtles use both ammonia and urea
trimethylamine oxide (TMAO)
Also, depending on the temperature and availability of water, tortoises can
- TMAO protects protein damage via urea
use uric acid or urea.
- Hyperosmoticity of the shark’s body enables the net
Osmolarity determines net movement of water across permeable
movement of water from the environment to its body
membrane; osmotic pressure
Maintaining water balance in fresh water
Isoosmotic- no net movement, but water moves in the same rate between
the environments Problem is opposite that of sea water environment, water is continually
gained and salt is continually lost
Hyperosmotic- higher solute concentration

5. - Amoeba and Paramecium have contractile vacuoles that - Protonephridium- network of dead-end tubules lacking
regularly pumps out water internal openings
- Some freshwater fishes release very dilute amount of urine - Branch all throughout the body and the smallest branch is
and gain salt by eating salty food or active uptake o salt capped by a cellular unit called flame bulb
Question: how do migrating fishes like the salmon balance their internal - Flame bulb has a tuft of cilia that beat regularly and draw
environment when they are in the sea? In freshwater? water and solute
- Water and solute is filtered through the flame bulb before
entering the tubule system
Anhydrobiosis- a dormant state when all water in the body is lost
- The urine exits the body through openings called
- Dehydrated cells are found to have trehalose that protects nephridiopores
the membrane and proteins of the cell
- The flame bulb system functions mainly in osmoregulation
Maintaining water balance on land
- Metabolic wastes either diffuse across the body surface or
Adaptations: used of waxy cuticle that decreases water loss excreted to the gastrovascular cavity and eliminated through
the mouth
- Exoskeletons of arthropods, shells of land snails, keratinized
skin of vertebrates - Parasitic flatworms that are isoosmotic with their
environment use their protonephridia on disposing
- Nocturnal adaptation to warm climate nitrogenous waste
- Diet of high water-yielding food that metabolically produce - Protonephridia is also present in rotifers, annelids, larvae of
large amount of water molluscs, lancelets
Metanephridia- has internal openings that collect body fluids
Excretory systems - Found in most annelids, e.g. earthworms
Most Excretory systems produce urine by refining a filtrate derived from - A segment of a body of a worm has a pair of metanephridia
body fluids that is immersed in coelomic fluid and enveloped by
capillaries
Urine is produced in a two-step process- first is collection; next is
composition adjustment by selective reabsorption or secretion of solutes - The internal opening is called a nephrostome that collects
fluid from an anterior segment
Filtration- initial fluid collection uses filtration
- External opening is called the nephridiopore
- Selectively permeable membrane of transport epithelium
retain cells and proteins in body fluid - The metanephridia function in excretion and
osmoregulation
- Hydrostatic pressure forces water and other small solutes
(salts, sugars, amino acids, nitrogenous wastes) into the - As urine moves in the tubule of the metanephridia, essential
excretory system nutrients are reabsorb via the transport epithelium and is
returned to the blood
- Fluid in the filtration is called filtrate
- Nitrogenous wastes remain and are excreted through the
- Fluid collection via filtration is not selective; reabsorption of nephridiopore
essential molecules are needed, e.g. sugars, salts, amino
acids Malphigian tubules- open into the digestive tract and dead-end at tips that
are immersed in hemolymph
- Non-essential solutes and wastes are either left in the
filtrate or actively pumped into it - Function in osmoregulation and excretion
- Pumping of solutes also adjusts the movement of water that - Present in arthropods
can affect the concentration of the urine
- Transport epithelium that lines the tubule secrete solutes
Diverse excretory systems are variations on a tubular theme including nitrogenous wastes into the tubule
Protonephridia: Flame-bulb system - Water follows the solute into the tubule via osmosis and is
reabsorbed in the rectum
- Used by flatworms
Vertebrate kidneys- usually function in osmoregulation and excretion

6. - Hagfish kidneys have segmentally arranged tubules - The nephron and collecting duct is lined with transport
epithelium that process the filtrate to produce urine through
- Most vertebrates have compact, nonsegmented organs that absorption and reabsorption of various substances
have numerous tubules arranged in an organized manner
- Afferent arteriole- supplies blood to the nephron; capillaries
- Dense network of capillaries and ducts are present subdivides into the glomerulus
Nephrons and associated blood vessels are the functional unit of the - Efferent arteriole- arteries that converge from the
mammalian kidney glomerulus; subdivides into the peritubular capillaries that
surround the proximal and distal tubule
Renal artery and renal vein- supplies blood to the kidneys
- Vasa recta- capillaries that supply the loop of Henle
Ureter- duct where urine exits the kidney
Even if the capillaries and tubules are closely associated they do not
Urinary bladder- collects urine from the two ureters exchange substances directly
Urethra- tube where urine from the urinary bladder is emptied Question: How does the presence of a long loop of Henle enable the
conservation of water in animals with juxtamedullary nephron?
- Empties to the outside near the vagina in females or through
the penis in males
Structure and function of the nephron and associated structures
Renal cortex- outer region of the kidney
Renal medulla- inner region of the kidney
Nephron- functional unit of the kidney
- composed of a single long tubule and a ball of capillaries
called the glomerulus
Bowman’s capsule- the cup-shaped swelling of the blind end of the tubule
Filtration of the blood
- blood pressure forces fluid out from the glomerulus to the
lumen of the Bowman’s capsule
- the porous capillaries and special cell of the capsule called
podocytes are permeable to water and other solutes but not
blood or proteins
- filtration is nonselective and the filtrate mirrors the
composition of the blood plasma
Pathway of the filtrate
- from the Bowman’s capsule the filtrate passes through three
regions of the nephron: proximal tubule, loop of Henle,
distal tubule
- the distal tubule empties to a collecting duct
- the collecting ducts empty to the renal pelvis and in turn is
emptied to the ureter
- 80% of nephrons are cortical nephrons (have reduced loop
of Henle)
- 20% are juxtamedullary nephrons (well-developed loop of
Henle)
- Juxtamedullary nephrons allow the conservation of water