BIOL 371 Final

What is an advantage of multicellularity

- having an internal environment that can be regulated
- its less work for the cells

Homeostasis

-maintenance of a stable internal environment
- Regulation of variables : nutrients, gases, pH, waste products, water/solutes, volume, pressure, temperature

Negative Feedback Loop

- allows homeostasis to be maintained by regulating physiological variables with reference to a set point

receptor (sensor)

modified cells that monitor environment

Integrator

specialized cells that compare information to a set point of a physiological variable

Effectors

a system or systems that bring the variable back to the set point

External Cells

-face environment
- can be dead (superficial layers of skin)
- can be protected by acellular cuticle

Cells of exchange surfaces

- must be alive
- control access to internal environment
-found inside body, deal with aspects of external environment
- subject to abrasions therefore have rapid replication and lifespans

Internal Cells

- homeostasis regulates the internal environment
- not isoosmotic with external environment
- enables them to specialize

Osmoregulation

regulation of the internal osmotic (water/salt/waste) environment

Circulation

bulk flow (through specialized channels) of fluid within the body (water, solutes, nutrients, gasses)

Gas Exchange

exchanging gasses (fluid in bulk flow and cells) with the environment

pH reguation

controlling the proton concentration of body fluids

Diffusion

-tendency of molecules of one kind to move from a volume in which they are relatively abundant to one in which they are relatively rare (moving down concentration gradient)
-short distances, dissolved solutes

Ficks's Law

- diffusion rate across a membrane = D A dC/dX

- D= diffusion coefficient (depends on characteristics of solute and solvent, temp, etc)
- A= surface area of the membrane
- dC= Concentration difference across membrane
- dX= thickness of membrane
dC/dX is the force driving diffusion

Bulk Flow

mass movement over long distances due to mechanical (hydrostatic) pressure

concentration gradient

a spatial difference in the relative abundance of one type of molecule (or atom)

Osmolality

osmotic concentration of a solution, measured in osmoles

Osmoles

total number of dissolved particles of solute per kg of solvent

Hypoosmotic

a solution that has a LOWER osmolality than the reference solution

Lower concentration of solute, more solvent

Hyperosmotic

solution with a HIGHER osmolality than the reference solution

higher concentration of solute, less solvent

Isoosmotic

a solution with the SAME osmolality as the reference solution

Osmosis

the tendency of water to diffuse across a selectively permeable membrane towards the side of greater solute concentration when the membrane is impermeable to the solute

Osmotic potential

force exerted on water generated by differences in solute concentration across a semi permeable membrane

water moves from less negative to more negative volumes
more solute = more neg. osmotic potential

osmotic potential of water

0 ( highest possible )

Pressure Potential

hydrostatic (mechanical) pressure affecting how water crossses membrane from volume of high osmotic potential to low osmotic potential

What happens when pressure potential is OPPOSED to low osmotic potential

flow of water across membrane decreased, reversed or stopped

What happens when pressure potential is ADDED TO low osmotic potential

flow of water across membrane increased

Water Potential

sum of osmotic potential, pressure potential, gravity etc. across a membrane

Which osmotic environment do animal cells want to be in

isoosmotic

How does bulk flow in animals run?

the application of hydrostatic pressure

Osmoconformers

- adjust osmotic potential of cells and extracellular fluid to match environment


[Y] = [X] = [Z]

[Y] is [solute] inside cell
[X] is [solute] of the extracellular fluid
[Z] is [solute] of environment

Osmoregulator

-adjust osmotic potential of extracellular fluid to match cells and regulate or protect against the environment
- generally requires thick outer layer

[Y] = [X] ≠ [Z]

Marine Bony Fish

- hypoosmotic to environment
(lose H2O and gain ions through gills)

-drink seawater to compensate for H2O loss

- Chloride cells in gills eliminate Na+, K+, and Cl- from blood

- produce small amount of urine to conserve water, eliminate excess solute in feces

Freshwater Bony Fish

- Hyperosmostic to environment
(lose ions and gain water)

- do not drink

- large amounts of dilute urine

- must replace ions from food or from transport across a gill membrane

Elasmobranchs

- Isoosmotic to seawater
(concentrations of Na+, K+, Cl- less than seawater. difference made up by urea)

- still deals with inward diffusion of those ions through gills

- rectal gland secretes highly concentrated salt solution

Tonicity in a Dry Environment

- constant H2O loss through evaporation
(across wet respiratory membrane, surface of skin)

- water loss in urine and feces

What does water loss through urine and feces require?

- waterproofing of outer layer
- minimal exposure of gas-exchange + digestive surfaces to air
- minimizing electrolyte intake

Terrestrial environment

-dry
- lose water to environment
- consume/produce/ conserve water
- limit salt intake

Marine Environments

- hyperosmotic (dry)
- lose water to and gain salt from environment
- eliminate salt and consume/produce/conserve water
- limit salt intake

Freshwater Environments

- hypoosmotic
- gain water from and lose salt to the environment
- eliminate water and consume/conserve salt
- limit water intake

Excretion

- elimination of waste/toxins
- aids in controlling content of extracellular fluid (salt/water/pH)

Main means of excretion

- diffusion into water ( aquatic habitat only)

- Action of excretory tubule (liquid waste)

What are the 3 excretory actions of the excretory tubule?

1. Filtration (non-selective)
2. Secretion ( selective)
3. Reabsorption (selective)

Excretory Tubule

- composed of transport epithelium
- allows active transport of ions b/w ECF and filtrate
- other solutes and water diffuse in either direction

Ammonia (NH3) Excretion in Aquatic environments

- diffusion into the environment (across body/gills)
- Excretion in filtrate/urine

Ammonia (NH3) excretion in Terrestrial and some aquatic organisms

- produce urea (mammals, amphibians, sharks)
- produce uric acid (land snails, insects, reptiles/birds)

Protonephridium

filters extracellular fluid by means of a current produced by the ciliated flame cell

- fluid drains into a series of ducts
- reabsorption occurs in the ducts

Metanephridium

- filters coelomic fluid reabsorption into circulatory system through blood vessels

- associated with closed circulatory cystem

Malpighian Tubules

- lg. absorptive surface area in contact with haemolymph
- active secretion of uric acid, ions into lumen of tubule
-water follows through osmosis
- filtrate released into gut
- Na+ and K+ actively transported out, water follows
- solid uric acid released with feces

Nephron

- In vertebrates
- filters water and solutes from blood
- reabsorbs water and solutes to produce concentrated urine

Loop on Henle

important in formation of concentrated urine

Open Circulatory System

- low pressure and slow (suitable for slow metabolic rates)
- Hemolymph
- heart (s) sit in hemolymph-filled haemocoel
- directed flow to active tissues isn't possible

hemolymph

transport fluid in open circulatory systems, comes into direct contact with the tissues and extracellular fluid pool

Closed Circulatory System

- blood under pressure (regular)
- Blood vessels and heart form continuous closed circuits
- found in organisms able to sustain prolonged high activity rates
- Blood contained in vessels
- confinement makes pressure regulation, direction of flow and high flow rates possible

Arteries

-efferent vessels, carry blood away from the heart
- control blood distribution to the body by controlling vessel diameter (resistance)
- depulsate pressure waves from the beating heart

Veins

- Afferent vessels
- carry fluid BACK to the heart
- store blood (easily expand)

Capillaries

-exchange of substances between blood and tissues
(gas, fluids, solutes, nutrients, waste)
- morphology of wall permits
- diffusion
- huge cumulative surface area

Components of Blood (ECF) in Vertebrates

- Plasma
- Erythrocytes (red blood cells)
- Leukocytes (white blood cells)
- platelets

Ventilation (breathing)

- bulk flow between the respiratory medium (air/water) and the gas exchange surface (body surface/ lungs/ gills/ etc.
- must move lg. quantities of air/water over respiratory membrane
- gas enters/exits extracellular fluid bulk flow system by diffusion

Circulation

- bulk flow of ECF within the animal
- circulatory system must interact effectively with the gas exchange surface

Crosscurrent Exchange

- in birds
- air flows in ONE direction through the rigid lungs
- air sac system
- more effective than gas exchange in uniform pool exchange
-two cycles of ventilation necessary for one breath to clear system

What is the most used form of pH regulation in animals

bicarbonate buffering mechanism

bicarbonate buffering system

CO2 reacts with H2O to form carbonic acid (H2CO3)

- carbonic anhydrase facilitates this reaction in vertebrates
- in plasma H2CO3 dissociates into HCO3- (bicarbonate) and H+

Hyperventilation

-gets rid of CO2 faster than its produced
- shifts reaction to the left and lowers [H+]
- alkylosis

Hypoventilation

-conserves CO2
- shifts equation to the right and increases [H+]
- acidosis

What are the main obstacles animals had to overcome to live on land?

- Gravity
- Air
- Water
- Sunlight

Requirements for terrestrial life

- Desiccation avoidance
- Desiccation tolerance
- Excretion with limited water loss
- Gas exchange with air
- protect games from desiccation
- protect embryo from desiccation
- temperature extremes
- constraints on sensory systems
- support body weight

Cryptobiosis

formation of resistant stage (tun) in response to environmental challenges (dehydration, sub-zero temperatures)

Anhydrobiosis

when slowly desiccated, resistant tun formed. when rehydrated tardigrade returns to active state

Aestivation

prolonged period of decreased metabolism to avoid seasonal heat and drought

Disadvantages of breathing air

- CO2 doesn't diffuse into air as easily as into water
- inevitable evaporative water loss from internal respiratory surface (which must be kept wet)

Advantages of breathing air

- much more O2 than water
- atmospheric O2 diffused much more rapidly
- ventilation requires less muscular effort (low viscosity and density)

Insect tracheal system

- delivers air directly to tissues via interstitial fluid

- moist exchange surfaces

Vertebrate Lungs

- bulk flow of air to respiratory membrane
- moist internal exchange surfaces
- requires muscular effort

Amniotic Egg

- provides aqueous environment for developing embryo
- requires internal fertilization
- requires uricotely
- extra embryonic membranes support embryo
- shell porous to air, possibly to water

What are the two main ways that terrestrial animals regulate their body temperature?

- metabolic activity
- behaviour

Reasons for thermoregulation?

1. ice forming inside cells kill them
2. enzymes lose effectiveness outside ideal temp
3. performance depends on biochem processes occuring at their optimal temp

Endothermy

the production of sufficient metabolic heat to warm the tissues significantly

Ectothermy

insufficient heat from metabolic activities to warm tissues; heat must be exchanged with the environment

Heterothermy

allowing body temperature to vary

Homeothermy

tightly regulating body temperature around an unvarying mean

Endotherms

metabolic rate changes with temperature in order to maintain a constant body temperature

- an energetic cost

Ectotherms

metabolic rate changes directly with body temperature, which changes with environmental temperature

Conduction

direct heat transfer by contact

- air conducts heat poorly

Radiation

transfer of heat as long-wave light

- not very effective as heat sink but radiative sources are very effective at heating up

Convection

transfer of heat by a moving medium

- air or water flowing over an organism carries heat away or delivers it

Evaporation

energy consumed by a change from liquid to gas

effective way to carry heat away

How do cold-climate terrestrial endotherms conserve heat?

- Counter Current Heat Exchange Structures

Counter Current Heat Exchange Systems

- warm blood in efferent vessels heats cooled blood in afferent vessels

regional heterothermy

different body parts have different temperatures

Torpor

- reduces energy demand in endotherms during periods of low or high environmental temps or resource unavailability

- body temp set point DROPS
- metabolism Depressed

Hibernation

seasonal version of torpor during seasonal periods of low temp

heterothermic endotherms

- generate sufficient heat by the action of the flight muscles to maintain a high constant temp in the thorax

- tend to be furry

- ex: Bees

Freeze Avoidance

some ectotherms can supercool their ECF and let it go below 0 degrees w/o freezing

- mainly marine animals

Freeze tolerance

some terrestrial ectotherms can allow the bulk of their ECF to freeze for extended periods

How are organisms able to be freeze tolerant

- high intracellular osmolality
- depress freezing point
- control ice nucleation in ECF

Chemosensory Organs

require wet surfaces for absorption of air-borne chemical particles

Function of tympanal organs

pick up vibrations

Vertebrates hearing and balance

- organs for hearing, sensing acceleration and which direction is down are located in the inner ear