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A-Level Biology > 3.1.1 > Flashcards

3.1.1 Flashcards

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1
Q

Why do Amoeba not need specialised exchange surfaces?

A

All the Oxygen needed and Carbon diocjde produced can be exchanged with the external environment by diffusion - the distances the substances need to travel are very small.

1) Their metabolic activity if unicellular organisms is usually low thus the oxygen demands and CO2 production are low
2) SA:V ratio of the organism is large

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2
Q

Why do dolphins need exchange surfaces?

A

Metabolic activity is far higher
More energy needed moving through water (desner than air) - oxygen demands in muscles will be high and produce a lot of CO2
Distance is too far for effective diffusion to take place
Bigger organisms = smaller SA:V so gases cannot be exchanged fast enough

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3
Q

Surface area of a sphere

A

4(pi)r^2

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4
Q

Volume of a sphere

A

(4/3)(pi)(r)^3

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5
Q

The bigger the organism

A

Smaller SA:V becomes - distance substances need to travel from outside to reach cells in the centre increases ; harder to absorb O2

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6
Q

Characteristic features of gas exchange surfaces

A

Increased SA
Thin layers
Good blood supply
Ventilation to miamtain diffusion gradient

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7
Q

Increased Surface Area

A

Provides area needed for exchange and overcomes the limitations of SA:V ratio of larger organisms - root hair cells/villi

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8
Q

Thin layers

A

Diffusion dustances are short making process fast/efficient - alveoli in lungs and villi

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9
Q

Good blood supply

A

Steeper concentration gradient - faster the rate of diffison : ensuresthat substances are constantly delivered to and removed from the exchange surface. Maintains a steep concentration gradient for diffusion - alveoli/gills/villi

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10
Q

Ventilation

A

For gases it helps maingain concentration gradients and make the system more efficient - alveoli/gills of a fish

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11
Q

Why are gaseous exchange systems needed?

A

To allow mammals to exchange gases efficiently but minimise the amount of water lost from the body - for example alveoli are moist so oxygen can dissolev in water and be diffused, however this is also an ideal condition fro evaporation and water loss. NEED TO STRIKE A BALANCE

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12
Q

Humans

A

High metabolic rate
Homeostasis independent from the environment - a lot of O2 required for cellular respiration and production of CO2 needs to be removed

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13
Q

Structure of the gaseoues eschange system in humans

A

Nostril - nasal cavity - larynx - trachea - 2 bronchi - bronchioles - alveoli
Lungs have ribs on outside and intercostal muscles within with pleiral membrane even more within
Diaphragm is a band of muscle above abdominal cavity

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14
Q

Nasal cavity

A

Large surface area wirh a good blood supply - warming the air and increasinf humidity.
Hairy lining which secretes mucus (goblet cells) to trap dust wnd bacteria - protecting lungs from irritation and infection
Moist surfaces increase humidity of incoming air - reducing evaporation from the eschange surfaces (towards an area of high water potential)
After passing through nasal cavity, air engerinf lungs is of similar temperature and humidity

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15
Q

Trachea function

A

Main airway carrying clean and moist and warm air from nose down into chest - supported by rings of cartilage which prevent it from collapsing (like xylem). Rings are incomplete so that food can move easily down oesophagus BEHIND trachea

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16
Q

Trachea features

A

Lined with ciliated epithelial cells with goblet cells in between - they secrete muscus onto lining of trachea to trap dust and microorganisms thag have escaped the nose lining. Cilia beat and move the musuc along eith microorganisms away from fhe lungs - swallowed via throat and digested

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17
Q

Effect ofcigarette smoke

A

Stops cilia beating

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18
Q

Bronchus

A

Trachea divides to form left and right bronchus - similar to trachea with supporting rings of cartilage but smallerr

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19
Q

Bronchioles

A

Diameter < 1mm ; no cartilage rungs - walls are smooth muscle allowinf bronchioles to constrict (when muscles contract) and dilate (when they relax) - changes rhe amount of air reaching the lungs. Bronchioles are luned with a thin layer of flattened epithelium making some gaseous exchange possible

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20
Q

Alveoli

A

Tiny air sacs and consist of a thin layer of flattened squamous epithelial cells alonf with some collage and elastic fibres - 200-300 micromegers - elastin allows alveoli to stretch as air is drawn in and squeeze air out to restinf size = ELASTIC RECOIL

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21
Q

Main adaptations of alveoli

A

Large SA ; up to 500 million alveoli / adult lung. Alveolar SA is very large - increased rate of diffusion
Thin layers - both alveoli and capilalries are sinfle epithelial cell thick so diffusion distances between air in the alveolus and blood is very short
2 CELLS FROM ALVEOLI TO CAPILLARIES
Good blood supply - network of capillaries maintains constant flow of blood brining in Co2 and carrying off oxygen mainting steep concentration gradient between air and blood
Good ventilation - moves air in and out of algeoli helping maintain steep diffusion gradients for pxygen and carbon diocje between blood and air in lungs

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22
Q

Why do alveoli have lung surfactants?

A

Reduces surface tension at air and water interface - preventing collapse of structures and helping them remain inflated. Oxygen dissolves in water before diffusion but water can just evaporate - nasal cacity wtc prevnt loss of water in this way

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23
Q

What is ventilation?

A

Movement of air in and out of the lungs as a result of pressure changes in thorax

24
Q

Purpose of rib cage

A

Provides a semi-rigid case wifhin which pressure can be lowered with respect to air outside it

25
Q

Diaphragem

A

Broad domed sheet of muscle which forms floor of thorax

26
Q

External and internal intercostal muscles

A

Found between ribs

27
Q

Pleural membrane

A

Thorax is limed with pleural membranes which surround the lungs - pleural cavity (space between them) is filled with a lubricating fluid so membranes can easily slide over each other to breathe

28
Q

Inspiration - taking in air ; ACTIVE PROCESS

A

Dome shaped diaphragm contracts - lowerinf
External intercostal mysclss contract - moving ribs up and out
Volume of thorax increases
Presure decreases
Air is drawn through nasal passages, trachea, bronchioles into lungs from area of high preseure to low pressure outside of chest

29
Q

Expiration - PASSIVE PROCESS

A

Muscles of diaphragm relax so it moves up to restinf shape
External intercostal muscles relax so ribs move down and inwards under gravity
Elastic fibres of albeoli return tonormal length
Decreases volume
Inceeases pressure
Air moves out of lungs from high pressure to low pressure until equilibrium

30
Q

How can exhalation be active?

A

Can use energy to contract internal intercostal musclesoulling ribs down hard and fast - abdominal muscles contract forcing diapgragm up to increase pressure rapidly

31
Q

Why is first breath of a baby the hardest?

A

Lungs are enormously stretched as air flows in and elastic tissue never returns to its original length. Surfactants stop the lgeoli collapsing and sticking together ss the baby exhales - wihtout it the second breath would be just as difficult
Babies born at full term have all lung surfactants but only around the 30th week of preganncy that cells of alveoli start porsucing surfactant - premature babies may struggle to breath so a tiny amount is artificallybspreaged into lungs of a premature baby making breathing easier and preventing further lung damage

32
Q

Outside of insects?

A

Tough exoskeleton through which little or no gaseous exchange can take place

33
Q

Summary of different gaseous exchange system in insects?

A

Has evolved to deliver the oxygen directly to the cells and remove the Carbon dioxide in the same way ; no blood pigments to carry oxygen

34
Q

How does aur enter the insects?

A

Along thorax and abdomen there are many small openings known as spiracles - air enters and leaves the system through the spiracles but water is also lost - insects need to maximise efficiency of gas exchange but also minimise the loss of water. Spiracles can be opened or closed by sphincters which are mostly closed to conserve water

35
Q

When the ozygen demand is high…

A

Or when carbon dioxide levels build up, more of the spiracles open

36
Q

Tracheae

A

Largest tubes in insect system up to 1mm in diameter - they carry air into the body and run along the bidy of the insect. The tubes are lined by spirals of chitin which keeps them open if they are bent/pressed ; chitin is impermanle to gases so little gas eschange takes place in trachea

37
Q

Trachea branch to form…

A

Narrow tracheoles (0.6 micrometers) - each tracheole is a single greatly elongated cell with no chitin lining so they are freely permanle to gases ; they are very small so they run throguh tissues of insect running between individial cells and this is whete most of the gaseous exchange takes place between air and respiring cells

38
Q

How does air move along trachea and tracheoles?

A

Mostly through diffusion until it readhes the tissues - the vast number of tracheoles gives a large SA for gaseous exchange. Oxygen dissolves in moisture on walls of tracheoles and diffuses into surrounding cells - towards the end of tracheoles there is tracheal fluid which limits the penetration of air for diffusion. BUT when oxygen demands build up when insect is flying - there is a lactic acid build up due to anaerobic respiration which reduces water potential in respiring tissue ; causing water to move out of tracheoles exposing more SA for gas exchange

39
Q

What about larger insects?

A

Beetles locusts and grasshoppers have higher energy demands - especially when flying

40
Q

What methods do larger insects use to meer increased oxygen demand?

A

Mehcanical ventilation - air is actively pumped into sustem by pumping of thorax/abdomen (similar to inspiration). These movements change volume of the body causing pressure changes and thus air is drawn into trachea/tracheoles or expelled out
Collapse air sacs act as reservoirs to increase the amount of air moved through the system - they are usually inflated and deflated by movements in thorax and abdomen

41
Q

Advantage of animals in water?

A

They do not need to try and prevent water loss

42
Q

Difficulties of living under wate

A

Water is denser than air and much more viscous thus having s much lower oxygen content - fish have evolved very efficient systems - it would take too much energy to move water in and out of organs such as lungs. Moving water in one direction only is much simpler

43
Q

Why do fish need gills?

A

Bony fish are big thus low SA:V - they are also very active and have a high oxygen demand ; diffusion would not be enough to supply inner cells and their scales does not allow gaseous exchange. THEY MAINTAIN FLOW OF WATER IN ONE DIRECTION OVER THE GILLS

44
Q

Gill features

A

Large SA, good blood supply and thin layers. Gills are contained in a gill cavity covered by a protective operculum (bony flap) whcih is also active in maintaining a flow of water over the gills

45
Q

Gill arrangement

A

Gills have arches
Gill filaments occur in large stacks and need a flow of water to keep the, apart - exposing large SA needed for gas exchange
Gill lamellae are on the filaments - they have a rich blood supply and large SA ; main site of gaseous exchange for fish

46
Q

Direction of blood flow?

A

Efferent blood vessels carry the blood leaving the gills in the opposite direction to the incoming water - maintaining a steep concentration gradient

47
Q

Particular challenges of gills

A

Need to maintain a continuous flow of water over gills at all times even when they are not moving - need to carry out gaseous exchange as effectively as possible in water (diffusion is slower than in air)

48
Q

What must fish ensure with their gills?

A

That water is continually moving over it - more primitive cartilage fish such as sharks must keep moving (ram ventilation) to get water passing over the gills at all times. When bing fish are swimming this is fine but they have decliped an efficient system involving the operculum which allows them to move water overthr gills at all times

49
Q

How does water enter the fish?

A

Mouth opens and buccal cavity is lowered - increases volume - decreases pressure - pressure differential - water into cavity - operculwr valve is SHUT and cavity containing the gills expands which lowers the pressure in the cavity containing the gills.

50
Q

Water over the gills?

A

Mouth xloses - operculum opens and sides of the cavity move inwards - increases pressure in the opercular cavity and forces water over the gills and out of the operculum. Floor of buccal cavity moved up steadily to maintain a flow of water over the gills

51
Q

Main adaptations of gills

A

Large SA for diffusion - rich blood supply to maintain steep concentration gradients for diffusion - thin layers that diffusing substances have only short distances to travel

52
Q

How does overlapping gill filaments help?

A

Tips of adjacent gill filaments overlap to icmrease resistwnce to flow of water - slowing down movement and thus allowing more time for gaseous exchange to take place

53
Q

What does countercurrent flow do?

A

Water moving over gills and blood in golls flows in opposite directions to ensure a steep concentration gradient is maintained throughout compared to a parallel system - thus more gaseous exchange can twke place with bony fish removing about 80% of oxygen from the water flowing by
Cartilageous fish have parallel systems and can only extract 50% of oxygen

54
Q

Parallel system

A

Diffusion takes place until equilbirum is reached in oxyegn comcntratoon and thus no further net movement into blood

55
Q

Countercurrent system

A

Oxygen will ALWAYS be higher in water than in blood therefore always diffusion taking place - so much higher oxygen saturation in blood is achieved

A-Level Biology (37 decks)

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