BY2.2 Flashcards
(37 cards)
What happens to the Surface area:volume ratio as the organism gets larger
The surface area:volume ratio gets smaller
Why can’t large organisms use their external surface for gas exchange
The SA:V is too small, this means the external surface cannot supply O2 in a large enough quantity/rate to meet the high demand of the respiring cells, they have evolved specialised gas exchange surfaces
Why can small organisms use their external surface for gas exchange
- large SA:V = large enough volume of O2 for supply
- short diffusion pathway = high rate of diffusion
- low metabolic rate = low demand for O2
Why do large organisms have specialised gas exchange surface
- ensure a large volume of O2 can be supplied
* rate of O2 diffusion is fast
What properties do the 4 large organism have in their gas exchange surfaces
- large surface area = more diffusion of gases
- thin surface = short diffusion pathway
- moist = allows gases to dissolve - faster diffusion
- permeable to gases = allows gases to move across
- ventilation = maintain a concentration gradient
- good blood supply = maintain a concentration gradient
In fish where are the gills located
In the operculum cavity, protected by a ‘tough plate’ called the operculum
What are the specialised gas exchange surface in fish
Gill lamellae
How are the gill lamellae in fish adapted to gas exchange
- thousands of gill lamellae = high surface area (water must flow inbetween the filaments to spread them out, on land the filaments are compacted)
- thin = short diffusion pathway
- Permeable to gas
- good blood supply via the capillaries = circulates blood to maintain a concentration gradient between water and blood
Why do the fish gills have to be very well adapted
Because water is a denser medium compared to air, and has a 30x lower O2 concentration, therefore gills must be very well adapted for efficient absorption of O2 dissolved in H2O
What’s the main difference between parallel flow and countercurrent flow in fish lamellae
- Parallel flow = water and blood flowing in the same direction
- Counter current = water and blood flowing in opposite directions
Why is the counter current flow in fish gills more efficient compared to parallel flow
the concentration gradient between water and blood for O2 to diffuse is maintained along the whole length of the gill lamellae. Due to the fact that there is always a higher O2 concentration in the water, compared to the blood it meets, this means an equilibrium is never reached
What does the graph for parallel flow look like
O2 conc |
|
|
|\_\_\_\_\_\_\_\_\_\_
Distance over lamellae
\
| \_____ Top line = water
| / Bottom line = blood
|/________
What does the graph for counter current flow look like
O2 conc | \ \
| \ \
| \ \
| \ \
|\_\_\_\_\_\_\\_\_\_\_
Distance over lamellae
Top line = water
Bottom line = blood
What is ventilation
Ventilation is the movement of O2 containing medium (H2O/air) over the gas exchange surface in order to maintain a concentration gradient
In what way do fluids move in organisms
From a high pressure/small volume to a low pressure/large volume
How do organisms later the pressure in their bodies
Change the volume of chambers/cavities containing fluid
What happens during inspiration in a fish
- fish mouth opens
- muscles in buccal cavity floor contract to lower the buccal cavity floor
- increase of volume of buccal cavity
- decrease in pressure, lower than outside body, therefore water flows from high pressure to power pressure in buccal cavity
What happens during expiration in a fish
- fish closes mouth
- muscles in buccal cavity floor relax, causing the rise of the buccal cavity floor
- decrease in volume of the buccal cavity
- increase in pressure
What 2 factors do we need to consider when estimating the efficiency of gas exchange
- Surface area - supplying O2 to respiring tissues by diffusing
- Volume - demand for O2 by respiring cells
What is the specialised gas exchange of insects
Branched, chitin-lined system of tracheae with openings called spiracles.
Gas exchange surface are the tracheole tubes which come into contact with every tissue
How is a concentration gradient maintained in the gas exchange surface of Insects
Muscles in thorax and abdomen contract/relax causing rhythmical movements with ventilated the tracheole tubes, maintaining a concentration gradient
What are the advantages of the tracheal system
- every tissue is directly supplied with oxygen
- no haemoglobin is needed
- reduced water loss
What features or structures reduce the diffusion pathway and generate a high surface area in insects
Very highly branched = lots of tracheoles which touch the tissues
What is the tissue or structure which acts as gas exchange surface in mammals
Alveoli - made from epithelial cells
