Adaptations For Gas Exchange Flashcards
Definition of gas exchange
The diffusion of gases down a concentration gradient across a respiratory surface, between an organism and its environment.
Definition of respiratory surface
The site of gas exchange
Features of a respiratory surface
- large enough surface area , relative to volume of organism
- thin- diffusion pathway is short
- permeable- gases diffuse easily
- have a mechanism to produce a steep concentration gradient i.e. Bring in oxygen or removing co2 rapidly
Features of unicellular organism e.g. Amoeba ( single celled organisms)
- large SA: volume
- cell membrane is thin- diffusion into the cell is rapid
- thin- diffusion distances inside cell are short
What do unicellular organisms’ features allow them to do?
- absorb enough oxygen to meet respiration needs
- remove co2 fast enough to prevent high concentration build up and making cytoplasm to acidic for enzymes to work.
Why is the problem with larger organisms and gas exchange?
Lower SA: volume than smaller organisms
How are flatworms adapted for gas exchange?
Being flat they have a much larger surface area
No part of body is far from the surface- short diffusion pathway
How is an earthworm adapted for gas exchange?
- cylindrical- larger SA: volume than compact organism of same volume
- skin is respiratory surface, secretes mucus to keep moist, restricted to damp environment of soil
- low oxygen requirement- slow moving
- haemoglobin in blood, o2 round body, carries o2 away from surface- maintains gradient
Features of multicellular organisms:
- higher metabolic rate( more o2 needed)
- tissues and organism become more interdependent ( increase in size+ specialisation of cells)
- Ventilation mechanism- maintain steep concentration gradient
- respiratory must be thin. Inside your organism so the are protected
Problems for terrestrial organisms with gas exchange
- water evaporates from body surfaces- dehydration
- water molecules pass through gas exchange surfaces easily so are always moist- lose a lot of water
How are amphibians adapted for gas exchange?
Skin is moist and permeable
Well developed capillary network just below surface
Gas exchange through skin and lungs when animal is active
How are reptiles adapted for gas exchange?
Lungs have a complex internal structure, increasing SA for gas exchange
How are birds adapted for gas exchange?
Lungs process large amounts of oxygen- flight requires a lot of energy
Don’t have a diaphragm
Ribs and flight muscles ventilate lungs
How are folks adapted for gas exchange?
- one way current of water
- many folds- large SA
- large SA- maintained by density of water flowing through
Where are the gills in cartilaginous fish?
- gills in gill pouches
- 5 spaces in each side
- open at gill slits
Why is the gas exchange system less efficient in cartilaginous fish?
- water is not forced over gills- must keep swimming for ventilation
- parallel flow
Definition of parallel flow
Blood and water flow in the same direction at the gill lamellae, maintaining the concentration gradient for oxygen to diffuse into the blood only up to the point where concentrations are equal
- bloods oxygen conc is limited to 50%
- does not occur across whole gill lamellae
Describe the structure of bony fish
- internal skeleton made of bone
- gills are covered with operculum
How does ventilation maintain flow in bony fish?
- water is forced over gill filaments by pressure differences
Water potential in mouth is higher than in opercular cavity
How do bony fish take in water?
1 mouth opens
2 operculum closes
3 floor of the mouth is lowered
4 volume inside mouth cavity increases
5 pressure inside mouth cavity decreases
6 water flows in- external pressure higher than pressure inside mouth
How is water forced out over the gills in bony fish?
1 mouth closes 2 operculum opens 3 floor of mouth is raised 4 volume inside mouth cavity decreases 5 pressure inside mouth cavity increases 6 water flows out over the gills- pressure in mouth cavity higher than in opercular cavity and outside
Describe the gills in bony fish
- 4 pairs of gills
- each supported by gill arch made of bone
- Gill filaments- thin projections along each gill arch
What are gill lamellae?
Gas exchange surfaces on the gill filaments
Held apart by water flowing between them- provide a large SA for gas exchange
Out of water they stick together and collapse- less area is exposed and not enough gas exchange takes place
What is counter current flow?
Blood and water flow in opposite directions at the gill lamellae, maintaining the concentration gradient and therefore oxygen diffusion into the blood, along their entire length
What do gills provide for fish?
- specialised respiratory surface
- large surface area extended by gill filaments and gill lamellae
- a network of blood capillaries- allow efficient gas diffusion
Structure of the human breathing system
- thorax
- pleural membrane
- diaphragm
- ribs
- intercostal muscles
- trachea
- bronchi
- bronchioles
- alveoli
How do mammals ventilate their lungs?
- negative pressure breathing
- for air to enter the lungs, the pressure inside the lungs must be below atmospheric pressure
Describe inspiration/ inhalation
1 external intercostal muscles contract 2 ribs pulled upwards+ outwards 3 diaphragm muscle contracts- flattens 4 thorax volume increases 5 pressure in lungs reduced
Describe expiration/ exhalation
1 external intercostal muscles relax 2 ribs move downwards and inwards 3 diaphragm muscles relax, domes upwards 4 thorax volume decreases 5 pressure in lungs increase
Why is inspiration an active process
Muscle contraction requires energy
Function of lungs
Lung tissue is elastic
Lungs recoil and regain their original shape when not being actively expanded
Major part in pushing air out the lungs
Function of pleural membranes
Contains pleural fluid
Acts as a lubricant, allowing friction free movement against the inner wall of the thorax
Role of alveoli
Inside surfaces Coated with a surfactant
Prevent alveolar collapsing during exhalation when air pressure is low
Allows gases to dissolve before they diffuse in or out
How are alveoli adapted for gas exchange?
- large SA: volume
- gases dissolve in surfactant moisture lining alveoli
- walls made of squamous epithelium- 1 cell thick- diffusion pathway is short
- capillary network surrounds alveoli and maintains conc gradients
- capillary walls one cell thick
How does gas exchange take place in insects?
Through paired holes called spiracles
Trachea and tracheoles
Spiracles open and close
Hairs covering spiracles
How does gas exchange take place when insects are active?
Movements of abdomen ventilate trachea
Gas exchange takes place between tracheoles and muscle fibres
How is large SA of a significant?
Gas exchange= room for many stomata
Photosynthesis= capture as much light as possible
How is being thin significant for a leaf
Gas exchange = short diffusion pathway
Photosynthesis = light penetrates through leaf
How is cuticle and epidermis being transparent adaptive for a leaf?
Light penetrates to the mesophyll
How are palisade cells being elongated and packed with chloroplasts significant for a leaf?
Photosynthesis = can accommodate a large number and capture as much light as possible
How is chloroplasts moving and rotating significant for a leaf?
Photosynthesis = they move into the best positions for maximum absorption of light
How is air spaces in the spongy mesophyll significant for a leaf?
Gas exchange= allow oxygen and carbon dioxide to diffuse between stomata and cells
Photosynthesis = carbon dioxide can diffuse to photosynthesising cells
Describe stomata
Bounded by 2 guard cells with unevenly thickened walls
Inner wall thicker than the outer wall
Width of the stomata can change stomata control the exchange of gases
When do stomata close?
- at night- prevent water loss, insufficient light for photosynthesis
- bright light- heat would increase evaporation
- excessive water loss
