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biology > 3.1 - adaptations for gas exchange > Flashcards

3.1 - adaptations for gas exchange Flashcards

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1
Q

how does an organisms size relate to its SA:V ratio

A

larger organism = lower SA:V

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2
Q

how does SA:V affect transport of molecules

A

lower SA:V = further distance molecules must travel to reach all parts of organism
diffusion alone not sufficient in organisms w/ small SA:V

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3
Q

why do larger organisms require mass transport + specialised gas exchange surfaces

A
  • small SA:V
  • diffusion insufficient to provide all cells w/ required O2 + to remove all CO2
  • large organisms more active than smaller organisms
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4
Q

four features of an efficient gas exchange surface

A
  • large SA
  • short diffusion distance
  • steep diffusion gradient
  • ventilation mechanism
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5
Q

describe the gas exchange mechanism in amoeba

A
  • unicellular organism w/ large SA:V
  • thin cell membrane providing short diffusion distance
  • simple diffusion across cell surface membrane sufficient to meet demands of respiratory processes
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6
Q

describe the gas exchange mechanism in flatworms

A
  • multicellular organisms w/ relatively small SA:V (in comparison to amoeba)
  • flat surface provides large SA + reduces diffusion distance
  • simple diffusion sufficient to meet demands of respiratory processes
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7
Q

describe the gas exchange mechanism in earthworms

A
  • cylindrical, multicellular organisms w/ relatively small SA:V (in comparison to flatworms)
  • slow moving + low metabolic rate (require little O2)
  • rely on external surface for gas exchange
  • circulatory system transports O2 to tissues + removes CO2, maintaining steep diffusion gradient
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8
Q

define ventilation

A

movement of fresh air into a space + stale air out of a space to maintain a steep conc gradient of O2 + CO2

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9
Q

name the organ of gaseous exchange in fish

A

gills

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10
Q

what are gill filaments

A
  • main site of gaseous exchange in fish, over which water flows
  • overlap to increase resistance to flowing water, slowing it down + maximising gaseous exchange
  • found in large stacks (gill plates) + have gill lamellae which provide large SA + good blood supply for exchange
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11
Q

explain the process of ventilation in bony fish

A
  • buccal cavity volume increases + pressure decreases to enable water to flow in
  • contraction of buccal cavity forces water across gills
  • pressure in gill cavity rises, opening operculum
  • water leaves
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12
Q

how is a steep diffusion gradient maintained across the entire gas exchange surface in bony fish

A

due to counter current flow

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13
Q

define counter current flow

A

blood + water flow in opposite direction across gill plate

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14
Q

how does counter current flow maintain a steep diffusion gradient
what’s the advantage of this

A
  • water always next to blood of lower O2 conc
  • keeps rate of diffusion constant + enable 80% of available O2 to be absorbed
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15
Q

what type of flow is exhibited in cartilaginous fish

A

parallel flow

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16
Q

define parallel flow

A

water + blood flow in same direction across gill plate

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17
Q

compare counter current + parallel flow

A

counter current:
- blood + water flow in opposite directions
- steep diffusion gradient maintained, allowing diffusion of O2 across whole gill plate
- high rate of diffusion
- more efficient, more O2 absorbed into blood
- found in bony fish
parallel flow:
- water + blood flow in same direction across gill plate
- diffusion gradient not maintained, diffusion of O2 doesn’t occur across whole plate
- lower rate of diffusion
- less efficient, less O2 absorbed into blood
- found in cartilaginous fish, e.g: sharks

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18
Q

name + describe the main features of an insects gas transport system

A

spiracles - small external openings along thorax + abdomen through which air enters, + air and water leave gas exchange system
tracheae - large tubes extending through all body tissues, supported by rings of chitin to prevent collapse
tracheoles - smaller branches dividing off tracheae

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19
Q

what’s the main site of gas exchange in insects

A

tracheoles

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20
Q

describe the adaptations of the insect tracheal system to a terrestrial environment

A
  • spiracles can open + close to regulate diffusion
  • bodily contractions speed up movement of air through spiracles
  • highly branched tracheoles provide large SA
  • impermeable cuticle reduces water loss by evaporation
21
Q

describe ventilation of the tracheal system in insects

A
  • expansion of abdomen opens thorax spiracles (air enters) + closes abdominal spiracles
  • compression of abdomen closes thorax spiracles + opens abdominal spiracles (air expelled)
22
Q

compare gas exchange surface of an active + inactive amphibian

A

active - has simple lungs
inactive - relies on moist external surface

23
Q

how are mammals adapted for gas exchange

A
  • alveoli provide large SA + thin diffusion pathway, maximising volume of O2 absorbed from one breath
  • have plentiful supply of deoxygenated blood, maintaining step conc gradient
24
Q

describe the structure of + function of larynx

A

hollow, tubular structure located at top of trachea involved in breathing + phonation

25
Q

describe the trachea + its function in the mammalian gaseous exchange system

A
  • primary airway. carries air from nasal cavity down into chest
  • wide tube supported by C-shaped cartilage to keep air passage open in pressure changes
  • lined by ciliated epithelial cells which move mucus (produced by goblet cells) towards back of throat to be swallowed, preventing lung infections
26
Q

describe the structure of the bronchi

A
  • divisions of trachea leading to lungs
  • narrower than trachea
  • supported by rings of cartilage + lined by ciliated epithelial + goblet cells
27
Q

describe the structure of+ function of bronchioles

A
  • many small divisions of bronchi that allow passage of air into alveoli
  • contain smooth muscle to restrict airflow to lungs but dont have cartilage
  • lined w/ thin layer of ciliated epithelial cells
28
Q

what’s the primary gaseous exchange surface in humans

A

alveoli

29
Q

describe the alveoli in the mammalian gaseous exchange system

A
  • mini air sacs, lined w/ epithelial cells
  • walls one cell thick
  • good blood supply to maintain steep diffusion gradient
  • 300 million in each lung
30
Q

what are pleural membranes

A

thin, moist layers of tissue surrounding pleural cavity that reduce friction between lungs + inner chest wall

31
Q

define pleural cavity

A

space between pleural membranes of lungs + inner chest wall

32
Q

describe ventilation in humans

A
  • movement of fresh air into lungs + stale air out of lungs via inspiration + expiration
  • via negative pressure breathing
33
Q

what are internal intercostal muscle

A

set of muscles found between ribs on inside involved in forced exhalation

34
Q

what are external intercostal muscles

A

set of muscles found between ribs on outside involved in forced + quiet inhalation

35
Q

explain the process of inspiration + the changes occurring throughout the thorax

A
  1. external intercostal muscles contract (internal relax), raising ribcage
  2. diaphragm contracts + flattens
  3. outer pleural membrane moves out, reducing pleural cavity pressure + pulling inner membrane out
  4. alveoli expand, alveolar pressure falls below air pressure so air moves into trachea
36
Q

what’s surfactant

A

fluid lining the surface of alveoli that reduces surface tension + prevents collapse of alveoli in exhalation

37
Q

describe the function of the waxy cuticle

A

reduces water loss from leaf surface

38
Q

describe how the upper epidermis is adapted for photosynthesis

A
  • layer of transparent cells allow light to strike mesophyll tissue
  • epidermal cells synthesise waxy cuticle, reducing water loss
39
Q

where’s the palisade mesophyll layer located

A

directly below upper epidermis

40
Q

how is the palisade mesophyll layer adapted for photosynthesis

A

receives most light so contains greatest conc of chloroplasts

41
Q

how is the spongy mesophyll layer adapted for photosynthesis

A
  • contains air spaces reducing diffusion distance for CO2 to reach chloroplasts in palisade layer
  • contains some chloroplasts
42
Q

what’s the vascular bundle

A

vascular system in dicotyledonous plants consisting of 2 transport vessels, xylem + phloem

43
Q

why are vascular bundles important in photosynthesis

A

form large network to deliver water + nutrients to photosynthetic tissues + remove glucose

44
Q

describe how the lower epidermis is adapted for photosynthesis

A

contains many stomata enabling evaporation of water + inward diffusion of CO2

45
Q

what are stomata

A

small holes found on leaves that can be opened + closed by guard cells to control gas exchange + water loss

46
Q

summarise the malade theory

A

states that the accumulation or loss of malade + K+ ions by guard cells results in changes in turgor pressure that open or close stomata

47
Q

by what mechanism do K+ ions enter guard cells

A

active transport

48
Q

how does accumulation of K+ + malade ions affect guard cells

A
  • lowers water potential of guard cells
  • water moves in by osmosis
  • guard cells become turgid, opening stomata
49
Q

why is starch important for stomatal opening

A

starch converted to a late ions

biology (24 decks)

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