2.2 adaptions for gas exchange Flashcards
(157 cards)
1
Q
via what do organisms exchange gases (such as oxygen and carbon dioxide) with the atmosphere?
A
via a gas exchange surface
2
Q
what determines how much gas can be exchanged?
A
the surface area of the gas exchange surface
3
Q
why is there always a balance to be struck about the size of the gas exchange surface in terrestrial organisms?
A
- as organisms increase in size, a specialised gas exchange surface is required to increase the area available
- since this also increases the area available for water loss, there is always a balance to be struck between exchanging gases and water loss in terrestrial organisms
4
Q
why do larger organisms have a higher oxygen requirement?
A
- they have a greater number of cells
- more active
5
Q
what are the general characteristics of an efficient gas exchange surface?
A
- large surface area to volume ratio
- moist to allow gases to diffuse
- thin to provide a short diffusion distance
- permeable to gases
- steep diffusion gradient
additional features but not present in all organisms:
- good blood supply to maintain conc gradient (not single-celled organisms, insects or plants)
- ventilation mechanism to maintain concentration gradient (not single celled organisms, worms or plants)
6
Q
what are some additional features for gas exchange in organisms (but not present in all organisms)?
A
additional features but not present in all organisms:
- good blood supply to maintain conc gradient (not single-celled organisms, insects or plants)
- ventilation mechanism to maintain concentration gradient (not single celled organisms, worms or plants)
7
Q
what is an example of a single-celles organism?
A
Amoeba
8
Q
features of single-celled organisms:
A
- surface area is large enough to meet the needs of the organism
- and therefore materials can be exchanged directly accros its thin and permeable cell surface membrane
- as the cytoplasm is constantly moving, the conc gradient is always maintained
9
Q
how is material/gases transported into single-celled organisms? why?
A
directly across its thin and permeable cell surface membrane
bc the surface area is large enough to meet the needs of the organism
10
Q
how is the concentration gradient in single-celled organisms (e.g Amoeba) maintained?
A
as the cytoplasm is constantly moving
11
Q
why is diffusion across the body surface in larger organisms insufficient to meet the needs of the organism?
A
- the surface area to volume ratio decreases
12
Q
how is the problem of where animals are very active and therefore have a higher metabolic rate, their oxygen requirements cannot be supplied by the body surface alone, solved?
A
- by the presence of a specialised gas exchange surface with a ventilation mechanism that ensures that the conc gradient is maintained across the respiratory surface
13
Q
what is one consequence of maintaining a moist respiratory surface in terrestrial animals?
A
water loss
14
Q
how is water loss minimised in terrestrial animals?
A
by having internal gas exchange surfaces, called lungs
15
Q
how have flatworms adapted for gas exchange?
A
- flattened body to reduce diffusion distance between the surface and the cells inside
- and which increases the overall surface area (like mitochondria)
16
Q
how have earthworms adapted for gas exchange?
A
- secretes mucus to maintain a moist surface
- has a well developed capillary network under the skin
- has a low metabolic rate to reduce oxygen requirements
- has a network of blood vessels and blood containing haemoglobin for the transport of oxygen (co2 is transported largely in the blood plasma)
17
Q
how have amphibians adapted for gas exchange?
A
- moist and permeable skin
- well developed capillary network beneath surface
- have lungs that are used when more active
18
Q
what are some examples of amphibians?
A
- frogs
- newts
19
Q
how have reptiles adapted for gas exchange?
A
- have internal lungs, like amphibians, but there are more complex and have a larger surface area
20
Q
what are some examples of reptiles?
A
- snakes
- crocodiles
21
Q
how have birds adapted for gas exchange?
A
- flight generates a very high metabolic rate and hence oxygen requirements
- to meet this, birds have an efficient ventilation mechanism to increase concentration gradient across the lung surface
22
Q
why do birds need to have an efficient ventilation mechanism to increase concentration gradient across the lung surface?
A
as flight generates a very high metabolic rate and hence oxygen requirements
23
Q
what are fish’s specialised internal gas exchange surfaces called?
A
gills
24
Q
what are gills made up of?
A
numerous gill filaments containing gill lamellae at right angles to the filaments
25
how do gill filaments that contain gill lamellae help in gas exchange?
- they greatly increase the surface area for the exchange of oxygen and carbon dioxide
26
in what way does gas exchange happen in cartilaginous fish?
by parallel flow
27
what is an example of a cartilaginous fish?
a shark
28
what is parallel flow?
blood and water flow in the same direction over the gill PLATE
(maintaining the conc gradient for oxygen to diffuse into the blood only up to the point where its concentration in the blood and water is equal)
29
in parallel flow, oxygen only diffuses into the blood up until what point?
where the concentration of oxygen in the blood and water is equal
30
how does parallel flow reduce the oxygen that can be absorbed into the blood?
gas exchange is only possible over part of the gill filament surface as an equilibrium is reached which prevents further diffusion and reduces the oxygen that can be absorbed
31
what is the ventilation mechanism in cartilaginous fish?
- as they swim, they open their mouth, allowing water to pass over the gills
32
in what way does gas exchange happen in bony fish?
by counter-current flow
33
what is counter-current flow?
blood and water flow in opposite directions at the gill lamellae
(maintaining the conc gradient and, therefore, oxygen diffuses into the blood, along their entire length)
34
whta is an example of a bony fish?
- a salmon
35
is parallel flow or counter-current flow a more efficient system?
counter-current flow
36
why is counter-current flow a more efficient system?
- because diffusion is maintained along the entire length of the gill filament/gas exchange surface
- because there is always a higher concentration of oxygen in the water than in the blood it meets, which results in higher oxygen absorption as an equilibrium is not reached
37
bony fish have a (more/less) advanced ventilation mechanism than cartilaginous fish?
more advanced
38
what is the ventilation mechanism in bony fish?
WATER FLOWS OVER GILLS BY PRESSURE CHANGES
water intake:
- mouth open
- floor of buccal cavity lowers
- opercular valve closed
- volume increases, pressure drops
- water flows in
- contraction of the buccal cavity forces water across the gills
water expulsion:
- mouth closed
- floor of buccal cavity rises
- opercular valve open/operculum opens
- volume decreases, pressure increases
- water leaves
39
bony fish have an internal bony skeleton
40
what is the flap that covers the gills of bony fish called?
the operculum
41
why do fish die out of water?
because the gills collapse and the filaments stick together, greatly reducing the surface area for absorption of oxygen
42
does more carbon dioxide diffuse from the blood into the water in bony fish or cartilaginous fish?
bony fish
43
what is the trachea supported by?
20 incomplete cartilaginous rings
44
the trachea, which is supported by 20 incomplete cartilaginous rings, branches into two ____, each entering a lung. they branch into finer tubes called ____, finally ending in ____ where gas exchange takes place
- bronchi
- bronchioles
- alveoli
45
when are the internal intercostal muscles used?
only during forced expiration
e.g blowing up a balloon or during exercise
46
what happens during inspiration in humans? (ventilation mechanism)
- external intercostal muscles contract (while internal relax)
- ribs move up and out
- which pulls the outer pleural membrane outwards
- diaphragm contracts and flattens
- this reduces the pressure in the pleural/chest cavity / thorax
- and the inner pleural cavity membrane moves outwards
- this pulls on the surface of the lungs
- and causes the alveoli to expand
- the alveolar pressure decreases to below atmospheric pressure
- so air is drawn in
47
what happens during expiration in humans? (ventilation mechanism)
- external intercostal muscles relax
- ribs move downwards and inwards
- allowing the outer pleural membrane to move inwards
- diaphragm relaxes and moves upwards
- this increases the pressure in the pleural cavity
- and the inner pleural cavity membrane moves inwards
- this pushes on the surface of the lungs
- and causes the alveoli to contract
- the alveolar pressure increases to above atmospheric pressure
- so air is forced out
48
is inspiration in humans passive or active?
active
49
is expiration in humans passive or active?
passive
50
how are the alveoli adapted for gas exchange?
- very large surface area FOR DIFFUSION ~ 700million alveoli
- very thin WALLS ~ 0.1um (one cell thick)
- surrounded by capillaries so short diffusion distance
- EXTENSIVE/LARGE CAPILLARY network
- good blood supply to maintain a steep diffusion gradient
- moist lining
- permeable to gases
- collagen and elastic fibres allow expansion and recoil
51
- a branch of the pulmonary ____ brings deoxygenated blood to the alveoli
- and a branch of the pulmonary ____ carried oxygenated blood from the alveoli back to the heart
- artery
- vein
52
what prevents the alveoli from collapsing and sticking together, and allows gases to dissolve?
a surfactant
53
how does a surfactant prevent the alveoli from collapsing and sticking together, and allows gases to dissolve?
(the alveoli produce a surfactant)
- which lowers the surface tension
54
why will a baby born before around 23 weeks have difficulty in breathing?
surfactant is not produced by the foetus until around 23 weeks of pregnancy
55
the gills are ___ times more efficient at extracting oxygen than the lungs?
why?
4 times
- this is due to the fact that water contains much less dissolved oxygen in it than is found in air
56
insects have a branched, chitin-lined system of tracheae with openings called ____?
spiracles
57
is the system of tracheae in insects branched or unbranched?
branched
58
how does the chitin help in gas exchange in insects?
- it’s arranged into rings
- it allows the tracheae to expand and contract
- and act like bellows drawing air in and out of the insect’s body
59
how is the chitin arranged in the gas exchange system of an insect?
it’s arranged into rings
60
where are spiracles found?
- found in pairs
- on segments of the thorax and abdomen
61
what can spiracles do?
- they can close during inactivity, and with the presence of chitin
- help to reduce water loss
62
tracheole tubes come into direct contact with what?
every tissue
supplying oxygen and removing carbon dioxide, so there is no need for haemoglobin
63
why is there no need for haemoglobin in insects?
tracheole tubes come into direct contact with every tissue, supplying oxygen and removing carbon dioxide
64
what are the ends of tubes filled with in insects?
fluid that allow gases to dissolve
65
how is a concentration gradient maintained in insects?
- muscles in the thorax and abdomen contract/relax
- causing rhythmical movements that ventilate the tracheole tubes, maintaining a concentration gradient
66
what do insects have an exoskeleton made of?
insects have an exoskeleton of chitin covered in wax, which is impermeable to water and gases
67
what limits insect size and shape? why?
the efficiency of the tracheal system in supplying oxygen to tissue limits insect size and shape
as it relies on diffusion, which is dependent upon diffusion distance
68
should a good blood supply as an adaption of gas exchange surfaces be included for insects?
no
they do not use it
69
why do plants require oxygen?
for respiration
70
why do plants require carbon dioxide?
for photosynthesis
71
how are carbon dioxide and oxygen obtained in a plant?
by diffusion through the leaf
72
how do plants reduce water loss?
- plants have a waxy cuticle that covers the surface of the leaf (which also prevents the diffusion of gases)
- plants have pores called stomata found on the underside of most leaves that can open during the day to allow gas exchange and close at night or during drought conditions
73
what is a disadvantage of the waxy cuticle that covers the surface of a leaf to reduce water loss?
it also prevents the diffusion of gases
74
what are the pores on the underside of most leaves called?
stomata
75
do stomata open or close during the day? why?
open during the day
- to allow gas exchange
76
do stomata open or close during the night? why?
- close at night (or during drought conditions)
- to reduce water loss
77
what is transpiration?
the evaporation of water vapour from the leaves, out through stomata
78
how can the size of the pore (stoma) between the guard cells be controlled to reduce water loss via transpiration?
by the guard cells that surround it
79
what surrounds the stoma in plants?
guard cells
80
stomata opening mechanism:
- guard cells photosynthesise producing ATP (in the chloroplasts in guard cells)
- energy released from ATP is used to actively transport potassium ions into guard cells
- this triggers starch (insoluble) to be converted to malate ions (soluble) (during photosynthesis some glucose is converted to starch)
- water potential of guard cell is lowered so water enters cells by osmosis (higher conc of K+ and malate ions, lower water potential in cytoplasm of guard cell)
- guard cells expand and outer wall stretches more than inner wall because it is thinner. this creates a pore between the two guard cells
- reverse happens at night
81
what do guard cells photosynthesise to produce?
ATP
82
what does the energy released from ATP get used for in the stomatal opening mechanism in plants?
the energy released from ATP is used to actively transport potassium ions INTO guard cells
83
what does potassium ions entering guard cells trigger? (in the stomatal opening mechanism)
starch (insoluble) to be converted to malate ions (soluble)
84
is starch insoluble or soluble?
insoluble
85
are malate ions insoluble or soluble?
soluble
86
in guard cells, does the inner wall stretch more than the outer wall?
no
the outer wall stretched more than the inner wall
87
in guard cells, why does the outer wall stretch more than the inner wall?
because it’s thinner
88
what are some adaptions of the leaf for gas exchange?
- leaves are thin and flat providing a large surface area to capture light and for gas exchange
- leaves have many pores called stomata to allow exchange of gases
- spongy mesophyll cells are surrounding by air spaces that allow gases to diffuse
89
air spaces in the spongy mesophyll layer, (increase/decrease) the rate of diffusion?
increase the rate of diffusion
bc it takes place in the gas phase
90
label/look at diagrams
91
magnification equation?
magnification=
size of image/actual size
i
m a
92
what is the correct scientific term for flowering plants?
angiosperms
93
what are the 2 main groups that angiosperms (flowering plants) are split into?
- dicotyledonous
- monocotyledonous
94
what is the main organ of gas exchange in all plants?
the leaf
(leaves are also the main site of photosynthesis)
95
what is the function of the cuticle on a leaf?
- waxy, waterproof that reduces water loss from the leaf surface
- transparent to enable light to penetrate to the mesophyll cells
96
what is the function of the upper and lower epidermis on a leaf?
- protection of tissue layers inside leaf
- transparent to enable light to penetrate
97
what is the function of the palisade mesophyll on a leaf?
- many cells can fit in the layer to maximise absorption of light
- large number of chloroplasts - increase absorption of light and therefore the rate of photosynthesis
98
what is the function of the spongy mesophyll on a leaf?
- cells contain some chloroplasts
- large number of air spaces for gas exchange within leaf - no ventilation mechanism so relies on diffusion
99
what is the function of the air spaces in a leaf?
- gas exchange of carbon dioxide and oxygen for respiration and photosynthesis
- water vapour evaporates into these spaces to maintain transport of water from roots to leaves
100
what is the function of the xylem on a leaf?
- transport of water and ions from roots to all other parts of the plant
101
what is the function of the phloem on a leaf?
- transport of carbon compounds (sucrose and amino acids) from the site of photosynthesis and storage organs to the rest of the plant
102
what is the function of the bundle sheath cells on a leaf?
- provides support and protection to the vascular bundles (in some plants the cells enable more efficient photosynthesis)
103
what is the function of the stomatal pores on a leaf?
- sites of gas exchange (carbon dioxide and oxygen) with the external environment
- water vapour lost from the stomata when open
104
what is the function of the guard cells on a leaf?
- control the opening and closing of the stomata
- contain chloroplasts
105
what is the function of the chloroplasts on a leaf?
- site of photosynthesis
- involved in the mechanism for stomatal opening and closing
106
how is concentration gradient maintained in leaves?
- for gases to move in and out of the leaves, there must be concentration gradients between the air in the air spaces and the air outside the leaf
- these are maintained by the balance between photosynthesis and respiration
107
what do gases (and water vapour) move into and out of leaves through?
the stomata
108
during the day, if the stomata are open, then the rate of photosynthesis is (high/low)? why?
high
as CO2 can diffuse in from the air and excess oxygen can diffuse out
109
at night, what takes place? (only respiration, only photosynthesis, both?)
only respiration takes place
110
are there chloroplasts in the guard cells?
yes
111
the inner wall of the guard cell is (thicker/thinner) than the outer wall?
the inner wall is thicker
112
what prevents the guard cell getting wider as they expand? (in leaves)
the hoops of cellulose
113
how does an organism’s size relate to its surface area to volume ratio?
the larger the organism, the lower the surface area to volume ratio
114
how does surface area to volume (SA/V) ratio affect transport of molecules?
- the lower the sa/v ratio, the further the distance molecules must travel to reach all parts of the organism
- diffusion alone is not sufficient in organisms with small sa/v ratios
115
why do larger organisms require mass transport and specialised gas exchange surfaces?
- small sa/v ratio
- diffusion insufficient to provide all cells with the required oxygen and to remove all carbon dioxide
- large organisms are more active than smaller organisms
116
describe the gas exchange mechanism in the Amoeba?
- unicellular organism with a large sa/v ratio
- thin cell membrane provides short diffusion distance
- simple diffusion across the cell surface membrane is sufficient to meet the demands of respiratory processes
117
describe the gas exchange mechanism in flatworms?
- multicellular organisms with a relatively small sa/v ratio (in comparison to the amoeba)
- however, flat structure provides a large surface area and reduces the diffusion distance
- simple diffusion is sufficient to meet the demands of respiratory processes
118
describe the gas exchange mechanism in earthworms?
- cylindrical, multicellular organisms with a relatively small sa/v ratio (in comparison to the flatworm)
- slow moving and low metabolic rate ∴ require little oxygen
- rely on external surface for gas exchange
- circulatory system transports oxygen to the tissues and removes carbon dioxide, maintaining a steep diffusion gradient
119
ventilation definition
the movement of fresh air into a space and stale air out of a space to maintain a steep conc gradient of oxygen and carbon dioxide
120
what are gill filaments?
- main site of gaseous exchange in fish, over which water flows
- they overlap to gain resistance to water flow - slows down water flow to maximise gaseous exchange
- found in large stack, known as gill plates, and have gill lamellae which provide a large surface area and good blood supply for exchange
121
compare counter current and parallel flow:
counter current flow:
- blood and water flow in opposite directions across the gill plate
- steep diffusion gradient maintained, allowing diffusion of oxygen across the whole gill plate
- high rate of diffusion
- more efficient - more oxygen absorbed into the blood
- found in bony fish
parallel flow:
- water and blood flow in the same direction across the gill plate
- diffusion gradient not maintained ∴ diffusion of oxygen does not occur across the whole plate
- lower rate of diffusion
- less efficient - less oxygen absorbed into the blood
- found in cartilaginous fish e.g sharks
122
name and describe the main features of an insect’s gas transport system:
- spiracles = small, external openings along the thorax and abdomen through which air enters, and air and water leave the gas exchange system
- tracheae = large tubes extending through all body tissues, supported by rings of chitin to prevent collapse
- tracheoles = smaller branches dividing off the tracheae
123
what is the main site of gas exchange in insects?
tracheoles
124
describe the adaptations of the insect tracheal system to a terrestrial environment:
- spiracles can be opened or closed to regulate diffusion
- bodily contractions speed up the movement of air through the spiracles
- highly branched tracheoles provide a large surface area
- impermeable cuticle reduces water loss by evaporation
125
describe the ventilation of the tracheal system in insects:
- expansion of the abdomen opens the thorax spiracles (through which air enters) and closes the abdominal spiracles
- compression of the abdomen closes the thorax spiracles and opens the abdominal spiracles (through which air is expelled)
126
compare the gas exchange surface of an active and inactive amphibian:
- active amphibian has simple lungs
- inactive amphibian relies on its moist external surface for gas exchange
127
how are mammals adapted for gas exchange?
- alveoli provide a large surface area and thin diffusion pathway
- maximising the volume of oxygen absorbed from one breath
- they also have a plentiful supply of deoxygenated blood, maintaining a steep concentration gradient
128
describe the structure and function of the larynx:
- a hollow, tubular structure located at the top of the trachea
- involved in breathing and phonation
129
describe the trachea and its function in the mammalian gaseous exchange system:
- primary airway, carries air from the nasal cavity down into the chest
- wide tube supported by C-shaped cartilage to keep the air passage open during pressure changes
- lines by ciliated epithelial cells which move mucus, produced by goblet cells, towards the back of the throat to be swallowed. this prevents lung infections
130
describe the structure of the bronchi:
- divisions of the trachea that lead into the lungs
- narrower than the trachea
- supported by rings of cartilage and lined by ciliated epithelial cells and goblet cells
131
describe the structure and function of the bronchioles:
- many small divisions of the bronchi that allow the passage of air into the alveoli
- contain smooth muscle to restrict airflow to the lungs but do not have cartilage
- lined with a thin layer of ciliated epithelial cells
132
what is the primary gaseous exchange surface in humans?
alveoli
133
what are the pleural membranes?
- thin, moist layers of tissue surrounding the pleural cavity that reduces friction between the lungs and the inner chest wall
134
pleural cavity definition
the space between the pleural membranes of the lungs and the inner chest wall
135
describe ventilation in humans.
- the movement of fresh air into the lungs and stale air out of the lungs via inspiration and expiration
- via negative pressure breathing
136
what are internal intercostal muscles?
a set of muscles found between the ribs on the inside that are involved in forced exhalation
137
what are external intercostal muscles?
a set of muscles found between the ribs on the outside that are involved in forced and quiet inhalation
138
what is surfactant?
- a fluid lining the surface of the alveoli that reduces surface tension and prevents collapse of the alveoli during exhalation
139
describe how the upper epidermis is adapted for photosynthesis:
- layer of transparent cells allow light to strike the mesophyll tissue
- epidermal cells also synthesise the waxy cuticle, reducing water loss
140
how is the palisade mesophyll layer adapted for photosynthesis?
- it receives the most light so contains the greatest concentration of chloroplasts
141
how is the spongy mesophyll layer adapted for photosynthesis?
- contains air spaces that reduce the diffusion distance for carbon dioxide to reach the chloroplasts in the palisade layer
- contains some chloroplasts
142
what is a vascular bundle?
- the vascular system in dicotyledonous plants
- it consists of two transport vessels, the xylem and the phloem
143
why are vascular bundles important in photosynthesis?
- they form a large network to deliver water and nutrients to photosynthetic tissues and remove glucose
144
describe how the lower epidermis is adapted for photosynthesis:
- it contains many stomata which enable the evaporation of water and inward diffusion of CO2
145
by what mechanism do K+ ions enter guard cells?
active transport
146
how does the accumulation of K+ and malate ions affect guard cells?
- lowers the water potential of guard cells
- water moves in by osmosis
- guard cells become turgid, opening the stomata
147
why is starch important for stomatal opening?
starch is converted to malate ions
148
what particular difficulty do fish need to overcome that insects do not?
in water, there is a lower concentration of dissolved oxygen
149
what problems do insects face that fish do not?
many insects have a waterproof layer to reduce water loss but this also reduces gas exchange
150
what is the purpose of the cuticle around the body of insects?
it’s waterproof to prevent water loss
151
what is the purpose of the hairs at the opening of the spiracle in insects?
the hairs contribute to water loss prevention (reduce evaporation) and they prevent solid particles getting in
152
at what time of day do plants ONLY release carbon dioxide?
night because there’s no light so only respiration happens
153
why are stomata ls usually found on the underside of the leaf?
- to reduce water loss by evaporation
- because away from direct sunlight
154
why are the human respiratory systems (lungs) internal? [1]
to REDUCE water/heat loss
155
(photomicrograph of trachea and oesophagus in mammal - kinda joined together)
- the rings of chitin in an insect’s trachea are complete. the rings of cartilage in a mammal’s trachea are incomplete or ‘C-shaped’. use the information in the photomicrograph to suggest why the rings of cartilage in a mammal’s trachea are incomplete [1]
- allows trachea to collapse slightly when food passes down the oesophagus / allows peristalsis / increase in size of oesophagus caused by passage of food
156
what unit should be used for transpiration rate?
- mm^3 cm^-2 min^-1
157
using the normal equipment of a potometer, suggest one way in which the accuracy of the measurement could be improved other than by using a capillary tube with smaller graduations [1]
- time over a long distance
