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AS Biology > 2.8 - Adaptations for gas exchange > Flashcards

2.8 - Adaptations for gas exchange Flashcards

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1
Q

What is the defintition of gas exchange?

A

The diffusion of gases down a concentration gradient across a respiratory surface, between an organism and its environment.

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2
Q

Name 4 respiratory surfaces.

A
  • gills in fish
  • alveoli in the lungs of a mammel
  • tracheae of an insect
  • spongy mesophyll cells in leaves
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3
Q

What must a respiratory surface have in order for rapid diffusion?

A
  • have a large enough surface area relative to the volume of the organism
  • be thin so that the diffusion pathway is short
  • be permeable so that the respiratory gases diffuse easily
    -have a mechanism to produce a steep conc gradient across the respiratory surface, by bringing oxygen or removing co2 rapidly
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4
Q

What must unicellular organisms have for diffusion?

A
  • single cells must have a large surface area to volume ratio
  • the cell membrane is thin so that diffusion into the cell is rapid
  • a single cell is so thin diffusion distances inside the cell are short
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5
Q

Why is it important that organisms are properly adapted for gas exchange?

A
  • absorb enough oxygen across the cell membrane to meet their needs for respiration
  • remove co2 fast enough to prevent building up a high concentration and making the cytoplasm too acidic for enzymes to function
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6
Q

Why is gas exchange less efficient in multicellular organisms?

A
  • they have a lower surface area to volume ratio than smaller organisms, so diffusion across their surfaces is not efficient enough for gas exchange
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7
Q

What is the example for gas exchange in a multicellular organism?

A

Earthworm
- cylindrical so less efficient surface area to volume ratio
- skin is respiratory surface which is kept moist, limiting its livable environments
- low oxygen requirement because it has a low metabolic rate
- haemoglobin is present in the blood, maintaining a diffusion gradient at its surface

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8
Q

What special features do multicellular organisms have?

A
  • higher metabolic rate, more oxygen and more co2
  • increase in cells means organs and tissues become more interdependent
  • must maintain a steep conc gradient in environmental and internal mediums
    -surfaces thin so easily damaged, so sum have developed protective features like rib cages or gills
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9
Q

What are the 2 main problems for terrestrial organisms?

A
  • water evaporates from body surfaces, which could result in dehydration
  • gas exchange surfaces must be thin and permeable with a large surface area. But water molecules are very small and pass through gas exchange surfaces, so gas exchange surfaces must be moist
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10
Q

Gas exchange features in amphibians?

A
  • frogs, toads and newts
  • their skin is moist and permeable, with a well developed capillary network just below the surface
  • gas exchange takes place through the skin and when an animal is active, in the lungs also
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11
Q

Gas exchange features in reptiles>

A
  • crocs, lizards and snakes
  • their lungs have a more complex internal structure than those of amphibians, increasing surface area for gas exchange
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12
Q

Gas exchange features in birds?

A
  • the lungs of birds process large volumes of oxygen because flight requires a lot of energy
    -birds do not have a diaphragm but their ribs and flight muscles ventilate their lungs more efficiently then the methods used by other vertibrates
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13
Q

What are the 3 key features of gills?

A
  • a one way current of water, kept flowing by ventilation
  • many folds providing a large surface area
  • water flowing through to prevent collapse
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14
Q

Why are cartilaginous fish less efficient than bony fish?

A
  • they don’t have a mechanism to force water over their gills so they must keep swimming
  • they have parallel flow (blood and water flow in the same direction at the gill lamellae mainting the conc gradient for oxygen to diffuse into the blood only up to the point of equlibrium at 50%)
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15
Q

What mechanism do bony fish have?

A

counter current flow
- blood and water flow in opposite directions at the gill lamellae maintaining the conc gradient and therefore oxygen and diffusion into the blood, along its entire lenth

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16
Q

What is meant by ventilation in fish?

A
  • to maintain a continuous, indirectional flow, water is forced over gill fillaments by pressure differences
  • the water pressure in the mouth cavity is high than the opercular cavity
  • the operculum acts as a valve, letting water out and acts as a pump, moving water past the gill filaments
  • the mouth also acts as a pump
17
Q

How do fish take in water?

A
  • the mouth opens
  • the operculum closes
  • the floor of the mouth is lowered
  • the volume inside the mouth increases
  • the pressure inside the mouth cavity decreases
  • water flows in, as the external pressure is higher than the pressure inside the mouth
18
Q

How do fish get rid of water?

A
  • the mouth closes
  • the operculum opens
  • the floor of the mouth is raised
  • the volume inside the mouth decreases
  • the pressure inside the mouth increases
  • water flows out as the external pressure is lower than the pressure inside the mouth
19
Q

What can gills provide?

A
  • a specialised respiratory surface, rather than using the whole body surface
  • a large surface extended by the gill filaments and gill lamellae
  • an extensive network of blood capillaries, with blood carrying haemoglobin, allowing efficient diffusion of oxygen into the blood and carbon dioxide out
20
Q

Describe the process of inspiration.

A
  • the internal intercostal muscles contract
  • the ribs are pulled upwards and outwards
  • at the same time, the diaghpragm muscles contract, so it flattens
  • both action increase thorax volume
  • this reduces the pressure in the lungs
  • atmospheric air pressure is now greater than the pressure in the lungs, so air is forced into the lungs
21
Q

Describe the process of expiration.

A
  • the external intercostal muscles relax
  • the ribs move downwards and inwards
  • at the same time, the diaphragm muscles relax, so they dome upwards
  • both actions decrease the thorax volume
  • this increases the pressure in the lungs
  • air pressure in the lungs is now greater than the atmospheric pressure to air is forced out of the lungs
22
Q

Describe the process of diffusion in the alveoli.

A

Deoxygenated blood enters the capillaries surrounding the alveoli, oxygen diffuses out of the air in the alveoli into the red blood cells of the capillary.
Carbon dioxide diffuses out of the plasma in the capillary into the air in the alveoli, from where it is exhaled

23
Q

How does gas exchange in insects work?

A
  • small surface area to volume ratio, cannot use skin to undergo gas exchange
  • gas exchange happens through holes called spiracles, running alongside the body
  • the spiracles lead to a system of branched, chitin lined tubes called trachae, which branch into smaller tubes called tracheoles
    -the spiracles can be opened and closed so gas exchange can take place and water loss can be reduced
24
Q

What happens gas exchange of plants in the day?

A

The rate of photosynthesis is faster than the rate of respiration due to increased sunlight
- more oxygen is produced in photosynthesis than in respiration, so overall the gas released is oygen

25
Q

What happens to gas exchange of plants at night?

A
  • photosynthesis does not happen so no oxygen is produced, so gas released is carbon dioxide
26
Q

Name the 8 features of a leaf that make it better adapted to gas exchange.

A
  • large surface area
  • thin
  • cuticle and epidermis are transparent
  • palisade cells are elongated
  • palisade cells are packed with chloroplasts
  • chloroplasts rotate and move within mesophyll cells
  • air spaces in the spongy mesophyll
  • stomatal pores
27
Q

How does a large surface area help gas exchange and photosynthesis in plants?

A
  • room for many stomata
  • captures as much light as possible
28
Q

how does being thin help gas exchange and photosynthesis in plants?

A
  • diffusion pathway for entering and leaving is short
  • light penetrates through the leaf
29
Q

How dies the cuticle and epidermis being transparent help a plant in photosynthesis?

A
  • light can penetrate through to the mesophyll
30
Q

Why are palisade cells elongated?

A

To accommodate a larger number in a smaller area

31
Q

Why are palisade cells packed with chloroplasts?

A

To capture as much light as possible

32
Q

Why do chloroplasts rotate and move within mesophyll cells?

A

The move into the best positions for maximum absorption of light

33
Q

Why are there air spaces in the spongy mesophyll?

A
  • allows oxygen and co2 to diffuse between the stomata and cells
  • allow co2 to diffuse to the photosynthesising cells
34
Q

How do stomatal pores help gas exchange?

A

They help gas exchange in and out of the leaf.

35
Q

What are the stomata?

A

Small pores on the above ground parts of plants and occur mostly on the lower surfaces of leaves, each pore is bounded by 2 guard cells.

36
Q

Why are guard cells unusual?

A

Guard cells are unusual because they are only epidermal cells with chloroplasts and have unevenly thickend walls

37
Q

What is the mechanism behind the opening and closing of the stomata?

A
  • if waters enters the guard cells, they become turgid and swell, and the pore opens
  • if water leaves the guard cells, they become flaccid and the pore closes
38
Q

Why do the guard cells open and close?

A
  • the chloroplasts in the guard cells photosynthesise and produce atp
  • atp provides energy for active transport of K+ ions into the guard cells from the surrounding epidermal cells
  • stored starch is converted into malate
  • the k+ and malate ions lower the water potential in the guard cells, making it more negative so water enters by osmosis
  • guard cells expand as they absorb water but less so in the areas where the cell water is thick (think gym resistance band, thicker = harder to move)
  • a pore appears in the areas that are less stretched, which is the stoma
39
Q

When will the stoma close?

A
  • at night, to prevent water loss when there is insufficient light for photosynthesis
  • in very bright light, as this is generally accompanied by intense heat, which would increase evaporation
  • if there is excessive water loss

AS Biology (11 decks)

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