animal respiration

Question 1

what is animal respiration

Answer 1

• energy for cells derived from that held within covalent bonds of organic molecules (energy rich bonds)
• cell respiration = chemical reactions, break bonds and release energy

Question 2

describe air as a respiratory medium

Answer 2

• air capacitance (ability to hold on and store) pf O2 and CO2 is the same in air
• 20x more O2 than water
• higher partial pressure than CO2, creates a gradient to diffuse across (reach equilibrium)

Question 3

describe water as a respiratory medium

Answer 3

• dense, viscous, less oxygen than atmosphere
• energetically challenging
• adaptations, highly efficient respiratory system (counter current), greater resistance to diffusion (influenced by temperature and salinity)
• CO2 is more soluble in water than O2, has capacitance for CO2 (carbonic acid, buffer)
• cold fresh water = more O2 than warm sea water

Question 4

what are the principles of gas exchange

Answer 4

• dissolved gases pass across membranes by diffusion
• respiration: exchanging of O2 and CO2
• proportion of dissolved gases depends on: partial pressure, solubility, temperature and salinity
• in large animals respiration (ventilation of respiratory structures) ties to a circulatory system (convection of fluid), CO2 and O2 must diffuse between membranes
• difference in partial pressures of gas on either side of membrane
• properties of membrane / permeability to the gas
• membrane SA for exchange (lungs and alveoli)
• thickness of membrane (thin, permeable = favoured)
• increase in V, SA does not increase at same rate and diffusion becomes ineffective - effective in small organisms / over short distances
• diffusion over distances greater than 2mm = specialised respiratory structures (trachea, external gills and lungs)

Question 5

describe the diversity of gas exchange surfaces

Answer 5

• body surface: gases diffuse into cells through body surface (invertebrates)
• tracheae: gases enter tracheae and diffuse into cells, don’t enter capillaries
• external gills: invertebrates / salamanders
• gills: one way flow, filter air from water
• lungs: two way flow, terrestrial vertebrates

Question 6

describe and open and closed circulatory system

Answer 6

• O: haemolymph surrounding body tissues acts as circulatory fluid
• C: interstitial fluid surrounding body tissues is distinct from blood acting as circulatory fluid

Question 7

what are gills

Answer 7

• structure: large, elaborate structures, outgrowth protected by rigid covering
• water flood keeps gill surfaces separated (increased SA)
• gill arches: support gills, hold them in place
• jaw: modification of anterior gill arches
• gill filaments: plate like extensions
• lamellae: cover filaments
• located under operculum
• ventilation (unidirectional): maintained by forcing water from buccal to operculum cavity
• water is drawn into mouth, passes over gills and exits through operculum
• forward movement through water also assists with gill ventilation
• counter current exchange

Question 8

what is the counter current exchange (gills) vs comparison flow

Answer 8

countercurrent exchange:
- blood flows in opposite direction to water passing over gills
- increases efficiency of gas exchange between ‘blood’ and respiratory media
- maximises difference in partial pressure of O2 in water and blood (partial pressure is always higher in water than blood)
- blood is always less saturated with oxygen than the water it meets
- strips respiratory medium of as much oxygen as possible
concurrent exchange:
- no maintenance of gradient
- O2 diffuses into blood due to large conc. gradient as blood has little O2
- eventually reaches an equilibrium where conc. is the same in blood and water and diffusion fluctuates around this medium
- maximum saturation of the water is 100% so the maximum saturation of the blood is 50%.

Question 9

what is the tracheal system

Answer 9

• extensive network of thin-walled tubes of chitin, further branches into tracheoles ending with fluid, close to mitochondria
• tubes supported by thickened spiral of chitin (taenidia)
• spiracles: valve-like hole in which air enters, valves reduce water loss
• muscular movement of body draws air into system
• limitation: like a snorkel, pipes must be short or wont meet the cells, diffusion

Question 10

what are lungs

Answer 10

• gas exchange takes place in alveoli of lungs (the blind ended sacs), relies on tidal flow of air in and out
• alveolar walls: thin, highly vascularised and coated with phospholipid surfactant (prevents collapse of alveoli walls)

Question 11

describe process of mammalian breathing

Answer 11

• mammals ventilate their lungs by negative pressure breathing which pulls air in
• lungs are ventilated when muscular diaphragm contracts to increase V
• which in turn decreases P in lungs and air flows from high to low pressure into lungs
• if this cavity is broken it loses the capacity to create the needed negative pressure.

Question 12

describe respiration in birds (lungs with a twist)

Answer 12

• unidirectional, not tidal
• parabronchi: gas exchange structures are associated with air sacs which have no respiratory function but act as bellows to circulate air internally
• air and water is cross current / concurrent (not bad, equivalent to what fish do)