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Biology A-Level > Gas Exchange > Flashcards

Gas Exchange Flashcards

1
Q

As an organism gets smaller, what happens to its surface area to volume ratio?

A

it gets bigger

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2
Q

Give 2 ways that organisms have evolved

A

-by having a large surface area accompanied by a flattened shape so that substances can diffuse the centre of cells quickly
-specialised exchange surfaces with a large sa to v ratio (e.g lungs)

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3
Q

what do specialises exchange surfaces all have?

A

-large SA to V ratio to increase rate of exchange
-thin to allow fast passage (diffusion) of substances
-movement of surrounding medium and internal medium to maintain diffusion gradient

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4
Q

why do exchange surfaces need to be inside organisms?

A

-prevent damage as they are essential for survival and are easily damaged as they are so thin

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5
Q

Why does the rate of diffusion increase with the square of the distance it has to travel?

A

In larger organisms, diffusion of substances would occur far too slowly to enable them to survive.

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6
Q

Why do single -celled organisms have a very large surface area to volume ratio?

A

Because the diffusion path is so short.

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7
Q

Why would a larger animal require more energy per day than a smaller animal?

A

it would have larger energy requiring systems

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8
Q

why would a larger animal require more energy per gram of body mass per day?

A

A larger animal has a larger surface area compared to its volume. it therefore loses heat energy more rapidly which increases its energy requirement per gram of body

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9
Q

How do multicellular animals overcome the limitations of diffusion?

A

By having a specialized circulatory system. This comprises:
-a heart
-a fluid in which substances are transported
-vessels through which the fluid can flow.

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10
Q

What happens during a closed circulatory system?

A

Blood is fully enclosed within blood vessels at all times.
From the heart, blood is pumped through a series of progressively smaller vessels. In the smallest vessels, capillaries, substances diffuse in and out of the blood and into cells.
Blood then returns to the heart via a series of progressively larger vessels.

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11
Q

What happens during an open circulatory system?

A

It consists of a heart that pumps a fluid called haemolymph through short vessels and into a large cavity called the haemocoel.
In the haemocoel, the haemolymph directly bathes organs and tissues, enabling the diffusion of substances.
heart
When the heart relaxes, the haemolymph blood is sucked back in via pores called ostia
Haemolymph moves around the haemocoel due to the movement of the organism.

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12
Q

What adaptations do insects have to reduce water loss?

A

-Waterproofing - exoskeleton with cuticle.
-Small surface area to volume ratio - smaller area over which water can be lost.

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13
Q

How is oxygen directly taken into respiring tissues in an insect?

A

Insects have spiracles which lead to a network of tubes called trachea which are supported by rings. They divide into smaller tubes called tracheoles which extend throughout all of the body tissue which is how oxygen diffuses in.

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14
Q

What are spiracles

A

The pores through which the gasses enter and leave the tracheae are called SPIRACLES. They are opened and closed by a valve. Water is lost when they are open so they are kept closed until gas exchange is required .

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15
Q

Describe gill structure

A

Gills are made of gill filaments which are stacked in a pile.

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16
Q

What are found at right angles to gill filaments and what do they do?

A

At right angles to the filaments are gill lamellae, which increase the surface area

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17
Q

How does countercurrent flow occur?

A
  • Blood and water flow in opposite directions:
  • Blood meets water with a high Oxygen concentration.
  • The Oxygen diffuses from the water into the blood.
This occurs whether the concentration of Oxygen in the blood is high or low because: blood with a high oxygen concentration still contains less oxygen than the fully loaded Water, and blood with little / no Oxygen has a lower concentration of Oxygen than the water, even when the water has lost most of its Oxygen.
HENCE:- there is always diffusion of Oxygen from water to blood in the counter current system.
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18
Q

What percentage of water diffuse into the fish’s blood as a result of counter current flow?

A

80%

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19
Q

Why do we breathe?

A

Animals need to maintain a concentration gradient across their exchange surfaces so that oxygen will diffuse into the blood and carbon dioxide will diffuse out.

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20
Q

How do fish maintain a concentration gradient?

A

Fish manage this by keeping a continuous stream of oxygenated water moving over their gills

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21
Q

How do animals maintain a concentration gradient?

A

In animals such as mammals and birds, a concentration gradient is maintained in the alveoli by the mechanism of ventilation.

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22
Q

What does the respiratory system contain ?

A

The respiratory system contains the organs(trachea, bronchi, brionchiole, alveoli)that allow us to get the oxygen we need and to remove the waste carbon dioxide

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23
Q

Why might some people struggle getting the oxygen they need?

A

Narrow tubes - ventilation restricted
Alveoli breaks down - cant exchange properly
Paralysis - muscles don’t work properly

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24
Q

What are the 2 types of ventilators?

A
  • Negative pressure ventilators
  • Positive pressure ventilators
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25
What happens during inspiration?
Ribcage moves up and out Diaphragm contracts and moves downwards Internal intercostal muscles relax and external intercostal muscles contract pressure decreases so volume of thorax increases
26
What happens during expiration?
Ribcage moves down and in Diaphragm relaxes and moves upward Internal intercostal muscles contract and external intercostal muscles contract pressure increases so volume of thorax decreases
27
What is pulmonary ventilation?
calculates the total volume of air that is moved into the lungs during one minute
28
what is the equation for pulmonary ventilation ?
29
What is your vital capacity?
The volume of exhaled air after a maximum inspiration
30
What are some special features of gas exchange surfaces?
Large Surface Area Moist Thin Membrane Good Blood Supply
31
What do specialised exchange surfaces all have?
Large surface area to volume ratio - increase rate of exchange. Thin to allow fast passage (diffusion) or substances. Partially permeable for selectable absorption. Movement of surrounding medium AND internal medium to maintain diffusion gradient.
32
Why do specialised exchange surfaces need to be inside of organisms?
Prevent damage as they are essential for survival and easily damages as they are so thin.
33
What are stomata?
On the underside of leaves are small holes, or pores, called stomata. A single hole is called a stoma.
34
Each stoma is surrounded by what?
Each stoma is surrounded by two guard cells, which control the opening and closing of the stoma.
35
How do the guard cells work?
When carbon dioxide levels are low inside the plant, the guard cells gain water and become turgid. They curve out, opening the stoma and allowing gases in and out. Water also evaporates through stomata. High carbon dioxide levels cause the guard cells to lose water, closing the stoma.
36
What are leaves designed for?
Leaves are designed for one thing - making food via photosynthesis
37
How are leaves designed for making food via photosynthesis?
Leaves are broad and flat to capture lots of light Veins carry water to the leaf and food away to the rest of thi plant (veins also support the leaf) Small holes called stomata in the underside of the leaf allow gases in and out
38
Why are plant roots spread out?
Roots are spread out, helping both absorption of water and minerals and with anchorage. The roots are covered with millions of tiny root hair cells. These have a very large surface area, allowing the roots to absorb large amounts of water and minerals
39
What is the structure of a leaf?
-waxy cuticle -upper epidermis -palisade mesophyll/ packed with chloroplasts -xylem vessel -spongy mesophyll layer -lower epidermis/ stoma/ guard cell
40
chloroplasts are?…
the site of photosynthesis
41
How are the adaptations of the colourless flattened cells of the epidermis and the colourless protective waxy cuticle important for photosynthesis?
-readily allow light to pass through the leaf surface to the photosynthetic tissue
42
How is the adaptation of the closely packed palisade cells with their numerous chloroplasts important for photosynthesis?
-maximises light absorption for photosynthesis
43
How is the adaptation of having numerous transport tissues permeate the leaf structure important for photosynthesis?
-allows water to be efficiently delivered to the photosynthetic cells
44
How is the adaptation of the extensive network of air spaces in the spongy mesophyll layer important for photosynthesis?
-provides for an easy passage of gases to and from the palisade cells and an efficient gas exchange system via the stomata
45
How does the adaptation of the regulation of the opening and closing of the stomata important for photosynthesis?
-allows for efficient gas exchange while, at the same time, reducing water losses through transpiration
46
What is Flick’s law?
47
Stomata are usually at the bottom of leaves. Why?
shaded to keep water loss by evaporation to a minimum.
48
When might guard cells close the stoma and why?
When the plant is in need of water - to conserve the water the plant does have.
49
What are phloem cells made from?
living cells
50
What do phloem cells do?
Phloem cells transport sugars produced in the leaves up and down the stem to growing and storage tissues.
51
What are xylem cells made from?
dead cells
52
What do xylem cells do?
Xylem vessels transport water and minerals up the stem from the roots to the shoots and leaves. This transport occurs in one direction only.
53
What is transpiration?
Transpiration is the loss of water by evaporation from plants. Plants lose water when they open the stomata in the leaves to let in carbon dioxide. Water always moves from an area of high concentration to an area of low concentration. This movement of water is a type of diffusion called osmosis. Air around the plant usually contains less water than the cells of the plant, so water evaporates into the air.
54
Aswell as transporting water, what else is transported during transpiration?
mineral ions, sugars and hormones which are dissolved in the water too
55
When does transpiration happen most quickly?
when it’s hot, dry, windy, sunny
56
Why does transpiration happen most when it’s hot, dry, windy and sunny?
hot-particles have more energy so move out of plant more quickly. dry-bigger osmosis gradient so plant loses water more quickly. windy-bigger osmosis gradient so plant loses water more quickly. sunny-particles have more energy so move more quickly.
57
Plants that live in hot, dry, windy, sunny conditions often have what?
a thicker waxy layer
58
What are Xerophytes?
plants adapted to surviving dry / arid conditions
59
What are the adaptations of xerophytes?
-Stomata are closed when the plant is not photosynthesising (hence no
CO2 is needed) and no water is lost. -Thick cuticle to prevent water evaporation. -Rolled leaves to reduce water potential gradient and hence loose less water. -Hairy leaves, again reduce water potential gradient. -Sunken stomata, again reduce water potential gradient. -Leaves with a reduced surface area to reduce water evaporation.
60

Biology A-Level (7 decks)

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