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Wjec Biology Unit 2 > 2.2 > Flashcards

2.2 Flashcards

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
How do bony fish expel water
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
How do sharks ventilate
Ram ventilation Swim with their mouths open so water moves into the mouth over the gill slits Must keep swimming
27
Ventilation in fish is a _______ pressure ventilation
Positive
28
What is parallel flow
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
What is countercurrent flow
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
Which type of fish have a more advanced ventilation mechanism and why
``` 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
Describe larynx
Voice box | Contains vocal cords - sounds produced
32
Describe trachea
Pipe that connects lungs to pharynx | C-shaped rings of cartilage to prevent trachea collapsing when pressures in lungs are negative
33
Describe bronchi
2 branch off the lower end of trachea Deliver air to each lung Rings if cartilage prevent collapsing
34
Describe bronchioles
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
Describe alveoli
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
Describe pleural membranes
Surround lungs Secrete pleural fluid Involved in negative pressure breathing
37
Describe ribs
Protect heart and lungs
38
Describe intercostal muscles
Sit between ribs | On contraction they raise the rib cage in ventilation
39
Describe diaphragm
Muscle that separates thorax and abdomen | On contraction it is pulled down in ventilation
40
41
What do goblet cells in ciliated epithelial layer of trachea do
Produce mucus to trap particles in inspired air | Cilia sweep mucus upwards to the pharynx so cannot reach lungs
42
Why are the rings of cartilage in the trachea incomplete
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
Importance of smooth muscle in the trachea
Allows trachea to reduce its diameter so coughs are more forceful - good when expelling material
44
45
Purpose of the surfactant in the alveoli
Reduce surface tension of the water and prevents the alveoli collapsing
46
Inspiration of mammals
• 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
Expiration of mammals
• 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
What are spiracles
Holes in the exoskeleton of insects
49
Purpose of chitin in trachea of insects
Prevents trachea collapsing
50
Gas exchange surface of insects
Tracheoles
51
Where do spiracles occur
Thorax and abdomen
52
Closing of spiracles
Have valves so can reduce water loss | Drop in carbon dioxide stimulates spiracles to close
53
Opening of spiracles
To exchange gases | Build-up of carbon dioxide stimulates the opening so carbon dioxide is released and oxygen diffuses in
54
Spiracular fluttering
Rapid partial opening of closing of spiracles to allows gases to enter and leave
55
How do insects ventilate air in
``` The abdomen expands Pressure inside is lowered Abdominal spiracles close Thoracic spiracles open Lower pressure in abdomen pulls air through thoracic spiracles ```
56
How do insects expel air
``` Abdomen contracts Volume lowered Pressure increases Thoracic spiracles closed Abdominal spiracles open Stale air is forced out of open spiracles ```
57
What happens during flight in the insect flight muscle
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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