unit 3 cram Flashcards
3.3.1 surface area to volume ratio:
1) list 4 general things that need to be transported in an organism and some examples
2) what are the different forms of active and passive transport?
3) in a tropical fishtank with a broken heater, explain if the small or large fish will die first?4) describe and explain the general features of specialised exchange surfaces?
exam questions:
a) the scale for plotting body mass is a logarithmic scale. explain why this scale was used to plot body mass:
b) describe the relationship between body mass and oxygen uptake
c) the zoologist measured oxygen uptake per gram of body mass. explain why he did this.
d) heat from respiration helps mammals to maintain a constant body temperature. use this info to explain the relationship between body mass & oxygen uptake (shown in graph)
1) respiratory gases: oxygen and carbon dioxide
excretory products: urea and carbon dioxide
ions, minerals, glucose, fatty acids, amino acids
2) passive: simple diffusion, facilitated diffusion, osmosis
active: active transport
3) the smaller fish as it has a larger sa: vol ratio and so heat energy will escape the quickest. the rate of exchange is faster.
4) larger sa:vol ratio: increased rate of exchange
thin and flat: short diffusion distance
movement of external environental medium: maintain a diffusion gradient
movement of internal medium: maintain a diffusion gradient
+ a partially selective membrane
a) varied range of body masses between the different animals
b) inversely proportional
c) size of the organism varies but this allows us to still compare
d) as the body mass increases, the oxygen uptake decreases. this is because the sa:vol ratio decreases as the body mass increases
3.3.2 gas exchange (part 1)
1) explain why there is a conflict in insects between the need to reduce water loss and to exchange gas?
2) describe 2 ways respiratory gases move in and out of an insects tracheal system?
3) what are the limitations of the tracheal system?
question (5)
a) how do single celled organisms exchange respiratory gases?
b) explain why this method of gas exchange is only possible in very small organisms
(c) explain two features of the flatworms body that allow efficient gas exchange?
this is about oxygen:
describe what happens when the spiracles are closed:
explain why:
describe what happens when the spiracles are open:
explain why:
this is about carbon dioxide:
describe what happens when the spiracles are open:
explain why:
describe what happens when the spiracles are closed:
explain why:
an insect lives in air. describe how the insect is able to obtain oxygen and limit water loss (6)
1) waterproof coverings (waxy cuticle) - cover the whole body surface and prevent water being lost through skin or an insect’s exoskeleton
smaller sa: vol ratio (for an insect) - less diffusion of gas in and also less of an area to lose water from
2) oxygen diffuses in down the concentration gradient when spiracles open to be used for respiration, mechanical ventilation (abdominal pumping) which are muscle movementd that cause mass air movements in and out of tracheae
3) limits the size of an insect because it relies on diffusion for exchange and diffusion needs a short diffusion path (the insect can’t get any larger)
a) by diffusion
b) since they have a larger sa: vol ratio
c) its thin flattened body not only gives a short diffusion pathway but also increases the sa: vol ratio
oxygen:
spiracles closed: when the spiracles are closed the oxygen levels decrease and then plateau
explain: it is used up in aerobic respiration
spiracles open: when there is a low amount of co2 and most of it’s been drawn out, o2 levels increase
explain: to allow o2 to diffuse down the concentration gradient
carbon dioxide:
spiracles open: co2 levels decrease
explain: co2 diffuses out of spiracles down a concentration gradient
spiracles close: co2 levels increase
explain: co2 produced in respiration
- the spiracles open and close to minimise water loss
- as well as open to allow o2 to diffuse down a concentration gradient
- air is also drawn through physical ventilation (abdominal pumping) which allows for mass flow
- body is covered with waterproof waxy cuticle so the insects have spiracles which open and close
3.3.2 gas exchange (part 2)
1)smaller organisms have a larger sa: vol ratio.. what does this mean for them?
2)larger organisms have a smaller sa: vol ratio.. what does this mean for them?
3) fill in the gap: single celled organisms exchange respiratory gases by diffusion _______________
the adult damselfly uses a tracheal system for gas exchange. explain three ways in which an insects tracheal system is adapted for efficient gas exchange (3)
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1) how do fish take in water?
2) problems for gas exchange in fish and what do the gills provide because of this?
3) describe the counter current mechanism
1) can just use diffusion for absorption
loses more heat to the environment so they need a higher metabolic rate ex. respiration
so they use more o2 per gram of tissue
2) can’t just use diffusion for exchanging molecules like oxygen and glucose etc
loses less heat to the environment so they don’t need a very high metabolic rate compared to smaller organisms
so they use less o2 per gram of tissue
3) through cell/body surface
- tracheoles have thin walls that are 1 cell thick for a short diffusion distance and an increased sa:vol ratio
- the tracheoles and the muscle fibres are close together for a short diffusion pathway
- many tracheoles which increase the surface area
- abdominal pumping allows for mass flow of oxygen
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1) water is taken in mouth, forced over gills, out of openings at side of the head
2) have a gas tight outer covering, have a small sa:vol ratio
so the gills provide a specialised internal gas exchange surface
3) - water and blood flow in opposite directions
- so water with a higher oxygen concentration meets blood with a lower oxygen concentration
- this maintains a constant concentration and diffusion gradient across the entire length of the gill filament
- and equilibrium is never reached so there is a constant diffusion of oxygen
3.3.2 gas exchange (part 3)
1) how is a plant leaf adapted to gas exchange?
2) what are the differences between gas exchange in a plant leaf and gas exchange in a terrestrial insect?
i give the adaptation you tell me how it reduces water loss:
a) stomata sunk in pits, layers of hairs on epidermis, curled leaves:
b) small leaves or pines:
c) reduced number of stomata:
d) thick waxy layer on epidermis:
e) densely packed spongy mesophyll:
1) has stomata that opens and closes (co2 in and o2 out) for it to diffuse down the concentration gradient
it is thin and flat to give a short diffusion pathway/distance and a large sa: vol ratio
2) insects..
- create mass flow
- have a smaller sa: vol ratio
plants…
- can’t create mass flow
- have leaves which give a larger sa: vol ratio
a) - traps a layer of humid air so there’s less diffusion of water vapour
- lowers water potential gradient
b) - lowers sa: vol ratio
- less diffusion of water vapour
c) - lowers surface area
- less surface area for diffusion of water vapour
d) - longer diffusion pathway
- less water loss by evaporation
e) - less space for water evaporation
3.3.2 gas exchange (part 4)
1) describe how oxygen in the air reaches capillaries surrounding alveoli in the lungs. details of breathing not required.
2) what does alveoli contain?
what do they allow the alveoli to do?
3) adaptations of alveoli:
4) describe and explain how the lungs are adapted to allow rapid exchange of oxygen between air in the alveoli and blood in the capillaries around them
5) describe and explain how the structure of the mammalian breathing system enables efficient uptake of oxygen into the blood
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6) describe the path by which oxygen goes from an alveolus to the blood
7) explain how one feature of an alveolus allows efficient gas exchange to occur
8) explain why ventilation of the lungs increases the efficiency of gas exchange
9) in the lungs, the alveoli are the site of gas exchange. a large number of small alveoli is more efficient in gas exchange than a smaller number of larger alveoli. explain why
10) just before a person starts to exhale, the composition of the air in an alveolus differs from the composition of the air in the trachea.
a) give 2 ways in which the composition would differ
1) - it goes trachea, bronchi, bronchiole
- air getting drawn in down pressure gradient, down diffusion gradient across epithelial cells
2) collagen and elastic fibres, elastic fibres allow alveoli to stretch during inhalation and then recoil during breathing out
3) - large surface area of alveoli and capillaries
- short diffusion distance provided by the thin walls of the alveoli and the 1 cell thick thin walls of capillaries
- red blood cells are flattened against capillary walls
- more time for diffusion as red blood cells slow down when passing through capillaries
- steep concentration gradient of gases to be exchanged as breathing constantly ventilates lungs and the blood circulates through capillaries aorund alveoli
4) - the many alveoli have a large surface area, the capillaries also have a large surface area so diffusion is faster
- the walls of the alveoli are thin squamus and the capillaries are 1 cell thick so allow for a short diffusion pathway
- more time for diffusion as red blood cells slow down
- ventilation and circulation maintain the concentration gradient so faster diffusion
5) - walls of capillaries/alveoli have flattened cells
- cell membrane permeable to gases
- intercostal msucles maintain a concentration gradient as they ventilate the lungs
- wide trachea/branching of bronchi provides efficient flow of air
- cartilage rings keep airways open
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6) oxygen diffuses to the squamus to the endothelial cells of the capillary to the blood
7) one cell thick epithelium (flattened squamus) means short diffusion pathway and so higher rate of diffusion
8) maintains concentratio n gradient so there is more oxygen which removes carbon dioxide between the alveoli and the capillaries
9) - larger surface area or an increased one and so greater/higher rate of diffusion
10) a - less oxygen, more co2, more water vapour
b - gas exchange takes place in alveoli not trachea
