Adaptation for Gas Exchange Flashcards
What is gas exchange?
The diffusion of gases down a concentration gradient across a respiratory surface, between an organism and it’s environment
Diffusion
Movement of molecules from a region of high concentration to a region of lower concentration until they are equally distributed (reach equilibrium)
What gases are involved in gas exchange?
Oxygen
Carbon Dioxide
Flatworm
- Aquatic, flat, larger surface area than spherical worms
- Large surface area to volume ratio - every part of body close to surface
- Short diffusion pathway
Earthworm
-Terrestrial organism, cylindrical so m
smaller SA:VR than flatworms
- Skin is the respiratory surface - keeps moist by secreting mucus
- It has a low oxygen requirement because it’s slow moving + low metabolic rate
- Hemoglobin -blood caries oxygen around the body - maintains steep concentration gradient
Amoeba
- Cell membrane is thin = rapid diffusion
- Single celled = short diffusion pathway + large SA:VR
Amphibians
- Inactive amphibian uses its moist skin for gas exchange
- Skin is moist and permeable - well developed capillary network just below skin
- Active amphibians use simple lungs - surface is highly folded which increases SA
Reptiles
-Skin is impermeable - they have lungs
- More complex folding in lungs than amphibians
- Ribs helps ventilation
Birds
- Worm blooded - high respiration rate
- lungs processes large amount of oxygen - flight requires a lot of energy
- Ribs and wing muscles ventilates the lungs
Birds
- Worm blooded - high respiration rate
- lungs processes large amount of oxygen - flight requires a lot of energy
- Ribs and wing muscles ventilates the lungs
How do mammals ventilate their lungs?
Mammals ventilate their lungs by negative pressure breathing. For air to enter the lungs, the pressure inside the lung needs to be under atmospheric pressure
Inspiration
Ribs and sternum raised
Diaphragm pulled down
Expiration
Ribs and sternum fall
Diaphragm raised
When inhaling
The external muscles …
Ribs move …
Diaphragm …
Thorax volume …
Contract
Upwards and Outwards
Contracts and flatten
Increase
When exhaling
The external muscles …
Ribs move …
Diaphragm …
Thorax volume …
Relax
Downwards and inwards
Relax and dome upwards
Decrease
When inhaling
Pressure in lungs …
Atmospheric air pressure…
Movement of air…
Reduce
Greater than pressure in lungs
Into lungs
When exhaling
Pressure in lungs …
Atmospheric air pressure…
Movement of air…
Increase
Less than pressure in lungs
Out of lungs
What is the gas exchange surface in mammals?
Alveoli
Describe alveoli
Provide a large surface area relative to volume of the body
Moist for gasses to dissolve
Thin walls - squamous epithelium - short diffusion pathway
each alveolus covered by and extensive capillary network
Oxygenated blood is carried away from the alveolus and CO2 returns - maintains a steep concentration gradient
What is Surfactant?
(anti sticking chemical) covers each surface of the alveoli
Its prevents the alveoli from collapsing
- Often given to premature babies to provent immature lungs from sticking together
Gas exchange in the alveolus
- Deoxygenized blood enters the capillaries surrounding the alveoli
- Oxygen diffuses out of the air in the alveoli into the red blood cells in the capillary
- CO2 diffuses out of blood plasma in the capillary into the alveolar air, from where it is exhales
The 2 different types of fish
Cartilaginous fish - made of cartilage e.g sharks
Bony fish - got bones
Where do boney fish live?
Fresh or sea water
What is the flap covering the gills in bony fish called?
Operculum
Ventilation in bony fish
To take water in
1. Mouth opens
2. Operculum closes
3. Floor of mouth is lowered
4. Volume inside mouth cavity increased
5. Pressure inside mouth cavity decreases
6. Water flows in (external pressure is greater than internal pressure)
How to force water over gills in bony fish?
- Mouth closes
- Operculum opens
- Floor of the mouth is raised
- Volume inside mouth cavity decreased
- Pressure inside mouth cavity increases
- Water flows out over gills (internal pressure is greater than external pressure)
What is each gill supported by?
gill arch/ gill bar
What are the thin projections along each gill called?
gill filaments
On the gill filaments are the gas exchange surface. What is the gas exchange surface called?
Gill lamellae/ gill plates
Gill lamellae / Gill plates
They provide a large surface area for gas exchange
(in water lamellae’s are separated, out of water they stick together causing the gills to collapse
What is the flow mechanism in bony fish called?
Counter current flow mechanism
Blood from the gill capillaries flows in the opposite direction to water
What is the flow mechanism in bony fish called?
Counter current flow mechanism
Blood from the gill capillaries flows in the opposite direction to water
Counter current flow
Water always has a higher concentration of oxygen than the blood. Oxygen will move from a higher concentration in water, into the blood by diffusion, down a concentration gradient. Blood will always come across water that has a higher oxygen concentration than it.
Cartilaginous fish
less efficient than bony fish - they have to keep swimming for ventilation to happen
Direction of blood flow and water in bony fish
Opposite - counter current flow
Direction of blood flow and water in cartilaginous fish
Same direction - parallel flow
Parallel flow
Oxygen diffuses from a higher concentration in water into blood untill the cons=centration of oxygen in blood (has reached equilibrium).
Insects
Terrestrial
To reduce water loss they have evolved rigid waterproof exoskeleton made of chitin which is covered by a waxy cuticle
They have a small SA:Vol ratio so can’t use diffusion for gas exchange
What is the name of the holes that insects require for gas exchange
Spiracles - holes running along the side of the body
Spiracles
They can open and close like valves which allows gas exchange to take place and they reduce water loss
Spiracles lead into a system of ……
Branched, chitin lined air-tubes called tracheae, which branch into smaller tubes called tracheoles
During periods of activity, such as flight what helps ventilate the tracheae?
Movement of the abdoment
Explain gas exchange in insects
Gas exchange takes place at the end of the tracheoles. Oxygen dissolves into the fluid and diffuses directly into the cells so no respiratory pigment pr blood circulation is needed. CO2 diffuses out by the reverse prosses
Gas exchange pathway in insects
ENTERS through the thorax spiracles
When the abdomen is expanded the thorax spiracles are open and the abdominal spiracles are closed. As the abdomen is compressed the thorax spiracles close and the abdominal ones open
Exits through the abdominal spiracles
