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BIOL371 Comparative Biology of Plants and Animals > Theme 3 Powell > Flashcards

Theme 3 Powell Flashcards

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1
Q

Significance of Homeostasis

A
  • Biochemical reactions sensitive to: Temperature, pH, [solute], [water], pressure
  • Organisms must regulate many internal variables: nutrients, gasses, pH, waste products, water/solutes, volume, pressure, temperature
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2
Q

Homeostasis – Negative Feedback Loops

A

Homeostasis is maintained by regulating physiological variables with reference to a setpoint

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3
Q

Homeostasis – Cell Location

A
  • Cell location– implications for how homeostasis is approached
  • External cells must face the environment: sometimes dead (i.e. superficial layers of skin)
  • But internalized ‘external’ cells must be alive – control access
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4
Q

Internal ‘external’ cells must:

A
  • have a rapid turnover
  • produce a lethal environment to microbes
  • be covered by secretions to isolate them from the environment
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5
Q

Internal cells: homeostasis regulates the internal environment

A
  • Reduces the amount of work cells have to do to maintain homeostasis if internal cells are not isoosmotic with the environment
  • Enables them to specialize
  • Regulate circulating fluids
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6
Q

Osmoregulation

A

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

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7
Q

Circulation

A

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

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8
Q

Gas Exchange

A

exchanging gasses with the environment

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9
Q

pH Regulation

A

controlling the [proton H+] of body fluids

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10
Q

Water potential

A
  • the tendency of water to move, due to osmotic, hydrostatic, gravity, humidity, etc
  • sum of osmotic potential, pressure potential, gravity etc.
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11
Q

Fick’s Law - Diffusion Rate

A

= D A dC/dX

D = diffusion coefficient – depends upon characteristics of solute and solvent, temperature etc.
A = surface area of the membrane, directly a function
dC/dX:
dC – concentration difference;
dX – thickness of the membrane

dC/dX is the force driving the diffusion

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12
Q

Osmolality

A
  • osmoles – total number of dissolved particles of solute per kg of solvent
  • osmolality – osmotic concentration of a solution, measured in osmoles
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13
Q

hypoosmotic

A
  • of a solution, having a lower osmolality than the reference solution
  • pure water is hypoosmotic to the red blood cell placed in it, which bloats
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14
Q

hyperosmotic

A
  • of a solution, having a higher osmolaity than the reference solution
  • a strong saline solution is hyperosmotic to the red blood cell placed within it, which shrivels
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15
Q

isoosmotic

A
  • of a solution, having the same osmolality as the reference solution
  • a bath of physiological saline is isoosmotic to the red blood cell placed within it, which stays the same
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16
Q

Osmosis

A

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

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17
Q

Osmotic potential (solute potential in plants) – force exerted on water generated by differences in solute concentration across a semi-permeable membrane

A
  • Pure water has an osmotic potential of zero – the highest osmotic potential possible
  • Lower osmotic potential is a negative number (the more solute, the more negative the osmotic potential)
  • Water moves from less negative to more negative volumes
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18
Q

Pressure potential

A

– hydrostatic (=mechanical) pressure affects how water crosses a membrane from a volume of high osmotic potential to a volume of low osmotic potential
- Low osmotic potential requires high pressure to stop water from moving in

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19
Q

Osmosis and the living cell

A
  • Significance to animals: cells will shrink or swell if not in an isoosmotic environment (without work on the cell’s part)
  • Significance to plants: Cells will develop turgor pressure (hydrostatic) as water enters, which limits further influx of water
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20
Q

Bulk Flow

A
  • Bulk flow of transport fluids requires application of hydrostatic pressure
  • Affects exchange of water between the bulk transport system and the extracellular fluid in closed circulatory systems
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21
Q

Bulk Flow - Animal Example

A
  • Pressure potential in the upstream side of the capillary bed exceeds the osmotic potential of extracellular fluid – water leaves capillaries
  • Osmotic potential in the downstream side of the capillary bed exceeds hydrostatic pressure of extracellular fluid – water re-enters capillaries
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22
Q

Osmoregulation in ANIMALS

A
  • Fresh water vs salt water vs plasma

- Osmoconformers vs Osmoregulators

23
Q

Osmoconformer Strategies

A
  • Adjust osmotic strength of cells [Y] and extracellular fluid [X] to match environment [Z]
  • Examples: marine inverts, hagfish, elasmobranchs
24
Q

Osmoregulators Strategies:

A
  • Adjust osmotic strength of extracellular fluid [X] to match cells [Y] and protect the internal environment from the external [Z]
  • Examples: freshwater inverts and most vertebrates
25
Q

The challenge of water/salt loss and gain

A
  • Terrestrial animals: (water loss)

- Aquatic animals: Marine (water loss), Freshwater (water gain)

26
Q

Tonicity And The Environment – Water Dwellers

A
  • Body fluid osmolality varies among aquatic organisms

- Some marine groups are isoosmotic with seawater – osmotically stable environment

27
Q

Marine bony fish

A
  • Hypoosmotic to the environment, lose water and gain ions, especially through the gills
  • Drink seawater to offset water loss
  • Chloride cells in gills eliminate Na+, K+ and Cl- from blood
  • Produce small amounts of urine, which conserves water and eliminates excess solute in feces
28
Q

Freshwater bony fish

A
  • Hyperosmotic to the environment, lose ions and gain water, especially through the gills
  • Do not drink
  • Produce large amounts of dilute urine
  • Must replace ions from food or from transport across gill membrane
29
Q

Chondrichthyes

A
  • Isoosmotic to seawater, but concentrations of Na+, K+, Cl- all less than seawater – the difference is made up by urea
  • Still must deal with inward diffusion of Na+, K+, Cl- through gills
  • The rectal gland secretes a highly concentrated salt solution
30
Q

Tonicity And The Environment – Land Dwellers

A
  • A dry environment = constant water loss through evaporation: across the wet respiratory membrane and across the surface of the skin
  • Water loss in urine and feces
  • Requires: waterproofing of outer layer of the body, minimal exposure of gas-exchange and digestive surfaces to the air, minimizing electrolyte intake
31
Q

Terrestrial environments are dry:

A
  • Lose water to the environment
  • Consume/produce/conserve water
  • Limit salt intake
32
Q

Marine environments are hyperosmotic (dry):

A
  • Lose water to and gain salt from the environment
  • Eliminate salt and consume/produce/conserve water
  • Limit salt intake
33
Q

Migratory salmon (Fresh to Marine to Fresh migrations)

A

Salmon in freshwater: chloride cells located on lamellae of gill filaments import electrolytes
Salmon in seawater: chloride cells located at base of gill filaments secrete electrolytes
- Basically: pump ions in in freshwater, then once in the ocean turn off those chloride cells for the other chloride cells which then pump out ions

34
Q

Controlling water loss and gain

A
  • Excretion: elimination of waste/toxins, aids in controlling the content of extracellular fluid (salt/water/pH)
  • Diffusion into water
  • Excretory organ (liquid waste): Filtration (non-selective), Secretion (selective), Reabsorption (selective)
35
Q

Ammonia (NH3) excretion

A
  • Ammonia is toxic = must get rid of it
  • Aquatic: diffusion into the environment (across body/gills), excretion in filtrate/urine, ammonium (NH+4)/sodium exchangers
  • Terrestrial (and some aquatic): cannot use diffusion or ion exchange with the air, only excretion in the filtrate
  • Produce Urea (mammals, amphibians, sharks)
  • Produce Uric Acid (land snails, insects, reptiles/birds): key for animals that develop in terrestrial eggs
36
Q

Malpighian Tubules

A
  • large absorptive surface area in contact with haemolymph
  • active secretion of uric acid, ions into the lumen of the tubule
  • water follows through osmosis
    filtrate released into the gut
  • Na+ and K+ actively transported out, water follows
  • Solid uric acid released with feces
37
Q

Why circulate fluids?

A
  • Processing: regulate pH, osmolarity, waste, add nutrients, gas exchange
  • Transportation/communication: hormones, heat, gasses, nutrients, immune components, solutes
  • Diffusion is adequate in small (>1 mm thick) or simple organisms, large require a circulatory system
38
Q

Plants vs Animals: Circulation

A

Both use a series of tubes, but differ in:

  • Nutrient, energy and water sources
  • Metabolic rates
  • Cell structure
  • Muscle (or not)
39
Q

CIRCULATION in Animals

A
  • Heterotrophs with a digestive system
  • High metabolic rates demand rapid circulation
  • Tissues require oxygen and nutrients
  • Respiratory wastes must be carried away
  • Muscular pump and flexible tubes for circulation: a cardiovascular system = Pump (cardio) and vessels (vasculature)
40
Q

Open circulatory system:

A
  • Low-pressure, slow – suitable for taxa with slow metabolic rates
  • May be supplemented with faster-specialized transport systems, ie. Tracheae in insects
41
Q

Hemolymph

A

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

42
Q

Open Circulatory System in Action

A
  • The heart(s) sit in haemolymph-filled haemocoel
  • On contraction, haemolymph expelled from the heart via major arteries to other haemolymph-filled spaces
  • On relaxation, haemolymph enters the heart from haemocoel
  • Valves in the heart wall maintain unidirectional flow
  • Further distributed by body movements – directed flow to active tissues not possible
  • Accessory hearts may supply limbs
43
Q

Closed circulatory system

A
  • Blood under pressure
  • Blood vessels and heart form a continuous closed circuit
  • Found in forms able to sustain prolonged high activity rates – annelids, cephalopods, some crustaceans, all vertebrates
44
Q

Blood contained within heart and vessels of the circulatory system, not coming in

A

direct contact with any of the tissues of the body

45
Q

Capillary beds connect

A

veins and arteries, permeating tissues

46
Q

Confinement makes what possible?

A

pressure regulation, the direction of flow and high flow rates possible

47
Q

The Heart – Muscular pump

A

Creates pressure in vasculature in closed circulatory systems, creates directional flow in open circulatory systems

48
Q

The Heart and Blood Vessels

A
  • The heart maintains the bulk flow of fluids in the face of resistance
  • Ohm’s law: flow = pressure / resistance
49
Q

In a closed circulatory system:

A
  • Blood pressure drops with distance from heart, due to greater volume occupied
  • Blood slows with distance from the heart, due to the smaller diameter of vessels occupied
  • Blood pressure drops due to greater friction and turbulence, lengths and diameters of vessels (resistance)
50
Q

Blood Vessels (in a closed system):

A

Arteries, veins, and capillaries

51
Q

Arteries

A
  • Carry fluid away from the heart
  • Control blood distribution to the body by controlling vessel diameter (resistance!)
  • Depulsate pressure waves from the beating heart (elastic – expand/contract)
52
Q

Veins

A
  • Carry fluid back to the heart

- Store blood (easily expand)

53
Q

Capillaries

A
  • Exchange of substances between blood and tissues (gas, fluids, solutes, nutrients, waste)
  • Designed to promote diffusion (and leaking in some tissues)

BIOL371 Comparative Biology of Plants and Animals (10 decks)

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