SA:V and gas exchange Flashcards
-examples of specialised exchange surface
-lungs
-gill
-lamellae of fish gills,
-tracheoles of insects;
-microvilli;
-state the relationship between the size of an organism or structure and
its surface area to volume ratio.
the larger an organism, the smaller the surface area to volume ratio.
the smaller an organisms the larger the surface area to volume ratio.
-why do large organisms have small SA:V ratio
-Rate of diffusion of substances from the body into the environment via skin is reduced.
This includes heat, so large animals loose heat slowly in cold climates.
Thus having lower metabolic rate.
-why do small organisms have large SA:V ratio
-Rate of diffusion across skin is increased so small animals lose heat more rapidly in hot climates.
-They have higher metabolic rate as more heat is generated and more heat is lost.
-What changes are made to the body shape and the development of systems in larger organisms as adaptations that facilitate exchange as this ration reduces?
-Thin membrane : short diffusion pathway ensures that materials can cross the exchange surface rapidly
-Partially permeable: only allows certain materials to pass through
-Movement of the internal and external environment: ensures concentration gradient is maintained.
-Large SA:V ratio: ensure maximum rate of reaction
-Adaptations of gas exchange surfaces across the body surface of single celled organism
-Large SA:V ratio
-Oxygen is absorbed by diffusion across their cell-surface membrane
-Carbon dioxide diffuses across body surface.
-Name structure through which gases enter and leave the body of an insect
Spiracles
-Name the small tubes that carry gases directly to and from cells of an insect
Tracheole
-three ways of moving gases in the tracheal system
1) Gas exchange by diffusion, as when cells respire, they use up oxygen + produce carbon dioxide, creating a conc gradient from the tracheols to the atmosphere
2) Insects contract and relaxes their abdominal muscles to move gases on mass
3) when the insect is in flight the muscle starts to respire anaerobically to produce lactate.
This lowers the water potential of the cells and therefore water moves from the tracheoles into the cell via osmosis
This decreases the volume in the tracheoles and as a result more air from the atmosphere is draw in
-Structural and functional compromises between the opposing
needs for efficient gas exchange and the limitation of water loss
shown by terrestrial insects
-when terrestial insects have their spiracles open they lose water vapour. This is important to minimise to prevent dessication
-so insects open and close their spiracles as required rather than keeping them open all the time
-they have hairs around the spiracles to trap a layer of water vapour, reducing the water vapour concentration gradient between tracheae and the atmosphere
-limitation of water loss; TERRESTRIAL INSECTS
-Insects have small SA:V where water can evaporate from
-Insects have a waterproof exoskeleton- water cannot evaporate out of their body expect spiracles
-spiracles : gases enter and water can evaporate from, can open and close to reduce water loss
-adaptations of insect’s tracheal system
1)large number of fine tracheoles -large surface area
2) walls of tracheoles are thin + short diffusion between spiracles + tracheoles -short diffusion pathway
3) use of oxygen and the production of carbon dioxide sets up steep diffusion gradients
-rate of diffusion calculated using Ficks Law
-surface area X difference in concentration
/ length of diffusion path
-gas exchange surface features
-large SA:V ratio
-short diffusion distance
- maintained a concentration gradient
-fish gill anatomy
-there are 4 layers of gills on both sides of the head
-the gills are made up of stacks of gill filament
- each gill filament is covered in gill lamellae, position at right angles to the filament
-creates a large surface area
-when fish open their mouth water rushes in and over the gills + then out through a hole in the sides of their head.
-adaptations of fish for efficient gas exchange
-large surface area to volume ratio created by many gill filaments covered in many gill lamellae
-short diffusion distance : due to a capillary network in every lamellae and very thin gill lamellae
-maintaining concentration gradient: countercurrent flow mechanism
-define countercurrent flow principle
when blood and water flow in the opposite direction over the gill filaments.
-what does countercurrent flow ensure
that a diffusion gradient is maintained across the entire length of the gill lamellae
-explain the advantage of the counter current flow (2)
1) diffusion gradient is maintained all the way across the gill lamellae
2) more oxygen will diffuse into the blood
Describe and explain the advantage of the counter current principle in gas exchange across the gill (3)
water and blood flow in opposite direction
maintains concentration gradient
across the whole length of the lamellae
-Describe and explain how the countercurrent system leads to efficient gas exchange across the gills of a fish
- Blood and water flow in opposite directions in the capillaries
- Concentration of oxygen in the blood is lower than in surrounding water, so oxygen diffuses into the blood
- Diffusion gradient maintained over full length of lamellae
The gross structure of the human gas exchange system limited to
the alveoli, bronchioles, bronchi, trachea and lungs.
Trachea - funnels the inhaled air into the lungs, while also facilitating the removal of inhaled air out of the lungs.
· Bronchi - smaller passages where air enters the lungs from the trachea.
· Bronchioles - The bronchi further divide into smaller, and smaller passages called bronchioles.
· Alveoli - thin-walled cells that are directly connected to capillaries. Oxygen are transferred down a concentration gradient from the alveoli, into the blood cells. At the same time, carbon dioxide is transferred from the blood cells to the alveoli
The essential features of the alveolar epithelium as a surface over which gas exchange takes place.
· Large surface area - many alveoli are present in the lungs with a shape that further increases surface area.
· Thin walls - alveolar walls are one cell thick providing gases with a short diffusion distance.
· Moist walls - gases dissolve in the moisture helping them to pass across the gas exchange surface.
· Permeable walls - allow gases to pass through.
· Extensive blood supply - ensuring oxygen rich blood is taken away from the lungs and carbon dioxide rich blood is taken to the lungs.
· A large diffusion gradient - breathing ensures that the oxygen concentration in the alveoli is higher than in the capillaries so oxygen moves
ventilation
ventilation is movement of air in and out of the lungs caused by muscles an active process involves mass flow & flow along air passages;
gas exchange
-diffusion of oxygen from the air in the alveoli into the blood and carbon dioxide from the blood into the air in the alveoli
Explain the need for a ventilation system
-draws fresh oxygen into the lungs
removal of CO2
-maintains concentration gradient of O2 / CO2 / respiratory gases
Identify two other adaptations that increase the rate of diffusion other than a steep concentration gradient
Large surface area - Efficient ventilation. - short diffusion pathway
How are the lungs adapted to maintain a steep concentration gradient?
-Constant ventilation to replace O2 and remove CO2
-Rapid blood flow to transport O2 away from the lungs and CO2 towards the lungs.
How do single celled organisms exchange gases
simple diffusion
Directly across the body surface
Why have multi-cellular organisms evolved and developed different exchange mechanisms to that of the single celled organism?
They are too large (Small SA:V ratio), diffusion pathway too long, rate of diffusion too slow.
How do tracheae facilitate gas exchange
- Air moves into the tracheae through the open spiracles
-O2moves down concentration gradient from the air to the cells
-CO2 moves down concentration gradient from the cells to the spiracles and then out into the atmosphere
-The tracheae branch off into tracheoles which have permeable walls
Where does gas exchange occur in plants and why?
in the leaf - adapted to have a large surface area
What mechanisms do plants and insects use to control gas exchange in order to limit water loss?
- spiracle control gas exchange in insects - stomata and guard cells control gas exchange in plants
-If the spiracles/stomata are left open all the time then water will leave the insect/plant via evaporation
-This will cause the organism to dry out and die
Why do xerophytic plants need adaptations to conserve water loss?
They live in areas that are very hot, dry or windy
One of the adaptations in some xerophytic plants is a layer of hairs on the epidermis around the stomata. How does this help survival in a desert environment?
- moisture is trapped around the stomata
-reduces the concentration of the water so less is lost from the leaf/ reduces water potential gradient
Identify two other adaptations found in some xerophytic plants that help them conserve water.
-fewer stomata
-waterproof/ waxy cuticles
The stomata close when the light is turned off. Explain the advantage of this to the plant
-water is lost through stomata
Closure prevents water loss
Maintain water content of cells.
the uptake of carbon dioxide falls to zero when the light is turned off
-No use of carbon dioxide in photosynthesis in the dark
-No diffusion gradient for carbon dioxide into leaf
adaptation of xerophyte plants
1) Thick waxy cuticle: reduces evaporation as less water can evaporate
2) Rolled up leaves: traps water vapour within the the rolled leaf and so has high water potential gradient
3) Hairy leaves: Traps moisture: reduces watere potential gradient between the inside and outside of the cell + therefore less water is lost by evaporation
4) sunken stomata: trap moisture + reduces water potential gradient
5) reduced SA:V rati: smaller the SA:V ratio - solwer the rate of diffusion
Describe two adaptations of the structure of alveoli for efficient gas exchange
-thin walls
-large surface area
the relationship between surface area to volume ratio and metabolic rate
·Small organisms, high metabolic rate, large surface area to volume ratio, lose heat faster than larger organisms.
-high rate of respiration to maintain their core body temperature
Adaptations of gas exchange surfaces, shown by gas exchange:
* across the body surface of a single-celled organism
very small diffusion distance, large surface area for efficient gas exchange
small size, single-celled organisms, high surface area where gas exchange can occur.
thin surface, diffusion pathway shorter
Adaptations in tracheal system of an insect (tracheae, tracheoles and spiracles)
· Trachea contains pores in its surface called spiracles air moves through spiracles
· Oxygen moves into the cell, down a concentration gradient
· the trachea branch off into smaller tracheoles.
· Like oxygen, carbon dioxide also moves down a concentration gradient, from the inside of the cell, to the spiracles. Eventually, carbon dioxide will be released into the atmosphere.
· Rhythmic abdominal movements facilitate the moving in and out of air in the spiracles
Adaptations by the leaves of dicotyledonous plants (mesophyll and stomata).
· small size, single-celled organisms have a high surface area where gas exchange can occur.
· thin surface, diffusion pathway shorter.
· mesophyll cells (middle leaf) which serves for gas exchange. contain pores called stomata that open to allow gas exchange, and close to control loss of water. controlled by guard cells
Structural and functional compromises between the opposing needs for efficient gas exchange and the limitation of water loss shown by Terrestrial insects and xerophytic plants.
· hairs in their epidermis to trap moist air around the stomata prevents loss of water
· Sunken stomata in pits capable of trapping moist air. Lowers the concentration gradient of water between the air and the leaf, lessening the tendency for water to evaporate away.
· Lower number of stomata to lessen sites where water can escape.
· waxy cuticle to reduce evaporation rat
Describe and explain the mechanism that causes lungs to fill with air.
Diaphragm (muscle) contracts and external intercostal muscles
contract;
(Causes volume increase and) pressure decrease;
Air moves down a pressure gradient
Describe the gross structure of the human gas exchange system and how
we breathe in and out.
1 - Trachea, bronchi, bronchioles, alveoli;
2- Breathing in - diaphragm contracts and external intercostal muscles contract;
3- (Causes) volume increase and pressure decrease in lungs
4- Breathing out - Diaphragm relaxes and internal intercostal muscles contract;
5- (Causes) volume decrease and pressure increase in lungs
