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Wjec Biology Unit 2 > 2.2 > Flashcards

2.2 Flashcards

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1
Q

What affects rate of diffusion

A

Surface area
Diffusion pathway
Concentration gradient

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2
Q

Unicellular organisms gas exchange

A

High surface area to volume ratio
Small distance to centre - short diffusion pathway
Dont need specialised gas exchange surfaces

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3
Q

What is the gas exchange surface of Amoeba

A

Cell membrane

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4
Q

Flatworms gas exchange

A 
Multicellular
Long and flat
High surface area:volume
Short diffusion path to centre of the body
No specialised gas exchange surface
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5
Q

Gas exchange surface of the flatworm

A

External body surface

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6
Q

Earthworms gas exchange

A

Multicellular
Terrestrial
Long cylindrical shape - high SA:V
Diffusion distance to centre is too large for diffusion alone to supply oxygen at a sufficient rate to sustain metabolic requirements
Closed Circulatory system - maintain diffusion gradients
Blood vessels close to external surface - short diffusion path to blood
No specialised gas exchange surface

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7
Q

What is the gas exchange surface of an earthworm

A

External body surface

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8
Q

Amphibia gas exchange

A

Multicellular animals
Aquatic and terrestrial modes of life
Thin moist skin
Closed circulatory system - at rest is it sufficient to supply the oxygen needs
Active - primitive lungs which are internal to reduce water and heat loss
Not highly folded like mammals but do increase SA

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9
Q

List the general features of specialised gas exchange surface of larger multicellular animals

A
  • large surface area
  • short diffusion pathway
  • ventilation mechanisms
  • permeability to gases
  • moist surfaces
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10
Q

Why are ventilation mechanisms needed in gas exchange

A

To maintain a concentration gradient

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11
Q

Why is a moist surface needed

A

Oxygen can dissolve in water and diffuse across gas exchange surface

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12
Q

What features of gas exchange surfaces help to maintain diffusion gradients

A

Ventilation mechanisms

Circulation of blood

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13
Q

What is the surface of fish covered in

A

Scales - impermeable to water and gases

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14
Q

Where do fish exchange gases

A

Gills - gill filaments and gill plates

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15
Q

What are gills covered by

A

Operculum

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16
Q

What does the operculum do

A

Open to let stale water out

Close to increase pressure within gill cavity during ventilation movements le

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17
Q

What does each gill cavity contain

A

4 gills supported on bony gill arches

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18
Q

Describe the structure of gills

A

Feathery

Consist of many gill filaments

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19
Q

What are the gill filaments covered with

A

Many lamellae/gill plates at right angles to increase surface area

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20
Q

Describe lamellae of fish

A

Very thin and close to capillaries - short diffusion path for oxygen and carbon dioxide

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21
Q

Function of gill rakers

A

Filter large particles out of the water preventing damage to delicate gill filaments

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22
Q

Where are gill rakers found

A

Other side of gill arches

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23
Q

Describe the blood supply of gill filaments

A

Rich blood supply

Contains haemoglobin

24
Q

How do bony fish take in oxygenated water

A

Mouth opens
Operculum closes
Buccal cavity floor lowers - volume increasing and pressure decreasing in cavity
Water flows into the buccal cavity as water pressure is higher than in buccal cavity

25
Q

How do bony fish expel water

A

Mouth closes
Floor of buccal cavity raises- volume decreases and pressure increases
Water flows across gills and enters opercular cavity
Operculum opens due to pressure
Water leaves fish through operculum - forces water over gills as opercular pressure is greater than external pressure

26
Q

How do sharks ventilate

A

Ram ventilation
Swim with their mouths open so water moves into the mouth over the gill slits
Must keep swimming

27
Q

Ventilation in fish is a _______ pressure ventilation

A

Positive

28
Q

What is parallel flow

A

Blood and water flow in the same direction at the gill lamellae
Concentration gradient is maintained for oxygen to diffuse into the blood only up to the point where concentration in blood and water is equal

29
Q

What is countercurrent flow

A

Blood and water flow in opposite directions at the gill lamellae, maintaining the concentration gradient and oxygen diffusion into blood along their entire length

30
Q

Which type of fish have a more advanced ventilation mechanism and why

A 
Bony fish (counter-current) more than cartilaginous fish (parallel)
Diffusion is maintained along the entire length of the gill filament so more oxygen absorbed
31
Q

Describe larynx

A

Voice box

Contains vocal cords - sounds produced

32
Q

Describe trachea

A

Pipe that connects lungs to pharynx

C-shaped rings of cartilage to prevent trachea collapsing when pressures in lungs are negative

33
Q

Describe bronchi

A

2 branch off the lower end of trachea
Deliver air to each lung
Rings if cartilage prevent collapsing

34
Q

Describe bronchioles

A

Smaller branches from bronchi
Deliver air to all parts of the lung
Muscle permits constriction to control flow of air in and out of alveoli

35
Q

Describe alveoli

A

Site of gas exchange
Sacs of air surrounded by squamous epithelia
Massive surface area
Short diffusion path
Surrounded by capillaries to maintain concentration gradient

36
Q

Describe pleural membranes

A

Surround lungs
Secrete pleural fluid
Involved in negative pressure breathing

37
Q

Describe ribs

A

Protect heart and lungs

38
Q

Describe intercostal muscles

A

Sit between ribs

On contraction they raise the rib cage in ventilation

39
Q

Describe diaphragm

A

Muscle that separates thorax and abdomen

On contraction it is pulled down in ventilation

40
Q
A
41
Q

What do goblet cells in ciliated epithelial layer of trachea do

A

Produce mucus to trap particles in inspired air

Cilia sweep mucus upwards to the pharynx so cannot reach lungs

42
Q

Why are the rings of cartilage in the trachea incomplete

A

Allow the trachea to collapse slightly when food passes down the oesophagus to increase the size of the oesophagus to food goes down easier

43
Q

Importance of smooth muscle in the trachea

A

Allows trachea to reduce its diameter so coughs are more forceful - good when expelling material

44
Q
A
45
Q

Purpose of the surfactant in the alveoli

A

Reduce surface tension of the water and prevents the alveoli collapsing

46
Q

Inspiration of mammals

A

• External intercostal muscles contract moving ribs up and out, which pulls
the outer pleural membrane outwards.
•Diaphragm contracts and flattens.
• This reduces the pressure in the pleural cavity and the inner pleural
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
Q

Expiration of mammals

A

• External intercostal muscles relax so 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
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
Q

What are spiracles

A

Holes in the exoskeleton of insects

49
Q

Purpose of chitin in trachea of insects

A

Prevents trachea collapsing

50
Q

Gas exchange surface of insects

A

Tracheoles

51
Q

Where do spiracles occur

A

Thorax and abdomen

52
Q

Closing of spiracles

A

Have valves so can reduce water loss

Drop in carbon dioxide stimulates spiracles to close

53
Q

Opening of spiracles

A

To exchange gases

Build-up of carbon dioxide stimulates the opening so carbon dioxide is released and oxygen diffuses in

54
Q

Spiracular fluttering

A

Rapid partial opening of closing of spiracles to allows gases to enter and leave

55
Q

How do insects ventilate air in

A 
The abdomen expands
Pressure inside is lowered
Abdominal spiracles close
Thoracic spiracles open
Lower pressure in abdomen pulls air through thoracic spiracles
56
Q

How do insects expel air

A 
Abdomen contracts
Volume lowered
Pressure increases 
Thoracic spiracles closed
Abdominal spiracles open
Stale air is forced out of open spiracles
57
Q

What happens during flight in the insect flight muscle

A

Available oxygen utilised rapidly
Anaerobic respiration takes place
Lactic acid produced
Water potential is lowered in the muscle cells
Water leaves tracheoles by osmosis
More air in contact with muscle cells
Higher rate of diffusion of oxygen into cells

Wjec Biology Unit 2 (5 decks)

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