Section 3-Exchange Flashcards
Do smaller or larger organisms have a large surface area to volume ration?
Smaller organisms
Why can the body surface act as an exchange surface in small organisms?
- Distances are short (less than 0.5mm)
- Surface area to volume ratio is large
Why can large organisms not rely upon their body surface for exchange?
- Distances are too great
- Relative surface area to volume is insufficient
What are the features of a specialised exchange surface?
- Large surface area
- Thin barrier to reduce diffusion distance
- Large concentration gradient
- Selectively permeable surface
What are the features of a specialised exchange surface?
- Large surface area
- Thin barrier to reduce diffusion distance
- Large concentration gradient
- Selectively permeable surface
What would the surface area to volume ratio of a cube that has side 10mm long be?
0.6
What are 3 factors that affect the rate of diffusion of substances into cells?
Surface area
Thickness of membrane
Permeability of membrane
Concentration gradient
Temperature
What is the heat exchange like in small organisms?
Heat is lost more easily - the relative surface area is large
Smaller organisms need high metabolic rate to generate enough heat
What is the heat exchange like in compact shaped organisms?
- Heat loss is minimised
* Small surface area relative to their volume
What is the exchange system called in insects?
The tracheal system
Where does air enter in insects?
-Through spiracles
Can be opened and closed- helps to reduce water loss.
What is the gas exchange structure in insects?
- Spiracle
- Trachea
- Tracheoles
- Muscle
How does an organisms surface area to volume ratio relate to their metabolic rate?
The smaller the surface area to volume ratio, the higher the metabolic rate.
How might a large organism adapt to compensate for its small surface area to volume ratio?
- Changes that increase surface area (e.g. folding)
- Body parts become larger (e.g. elephant’s ears)
- Elongating shape
- Developing a specialised gas exchange surface
Why can’t insects use their bodies as an exchange surface?
They have a waterproof chitin exoskeleton and a small surface area to volume ratio in order to conserve water.
What is the process by which carbon dioxide is removed from a single-celled organism?
Diffusion over the body surface
Why is there a conflict in terrestrial insects between gas exchange and conserving water?
Gas exchange requires thin permeable surface.
Conserving water requires thick waterproof surfaces.
Why does the tracheal system limit the size of insects?
It relies on diffusion to bring oxygen to respiring tissues.
If insects were large, would take too long for oxygen to reach tissues
Name and describe the 3 main features of an insect’s gas transport system.
Spiracles: holes in body surface, can open and close. For gas and water exchange.
Trachea: large tubes extending through all body tissues, supported by rings to prevent collapse.
Tracheoles: smaller branches dividing off the trachea.
What is the process of gas exchange in insects?
- Gases move in and out of trachea through spiracles
- Diffusion gradient allows oxygen to diffuse into body tissue while waste CO2 diffuses out
- Contraction of muscles in trachea allows mass movement of air in and out
Why can’t fish use their bodies as an exchange surface?
Have a waterproof, impermeable outer membrane and a small surface to volume ratio.
What are the gills made up of and what are they covered with?
Gill filaments
Covered with folds called lamellae
How are the lamellae specialised?
Short diffusion distance between water & blood (5um)
Increased surface area at right angles to gill filaments
Counter-current exchange system
What is a counter-current flow system?
Concentration gradient is maintained for whole length of lamellae ensuring uptake of diffusion can occur at all distances
Maintains favourable concentration gradient across entire exchange surface
What is the process of gas exchange in fish?
- Fish opens mouth to enable water flow in, shuts mouth to increase pressure
- Water passes over lamellae, oxygen diffuses into bloodstream
- Waster carbon dioxide diffuses into water and flows back out of gills
What is an advantage of one-way flow in fish?
Less energy required because flow does not have to be reversed
What are 3 adaptations of a leaf that allow efficient gas exchange?
- Thin and flat to provide short diffusion pathway and large SA:V
- Many stomata allow gases to easily enter
- Air spaces in mesophyll allow gasses to move around leaf (facilitates photosynthesis)
How do plants limit their water loss while still allowing gases to be exchanged?
Stomata open and close (regulated by guard cells)
What are 3 adaptations of insects to reduce water loss?
- Small surface area to volume ratio
- Waterproof covering
- Spiracles
How does a plant rolling its leaves help to reduce water loss?
Water evaporating from leaf is trapped, leaf becomes saturated with water vapour.
No water potential gradient so water loss is reduced.
What is the trachea?
Structure
- Flexible airway that is supported by rings of cartilage (prevents collapsing due to pressure)
- Lined with ciliated epithelial and goblet cells that produce mucus.
- Soft tissue allows trachea to be flexible
What is the bronchi?
Structure
- Allows passage of air into the bronchioles
- Supported by cartilage
- Lined with ciliated epithelial and goblet cells that produce mucus.
What are the bronchioles?
Structure
-Series of branching subdivisions off the bronchi
-Made of muscle, lined with epithelial cells
(Muscle allows them to constrict to control air flow)
What are the alveoli?
Structure
Small air sacs which provide a surface at which gas exchange occurs.
Lined with epithelium
How are the alveoli specialised for their role?
Covered with network of capillaries
Large numbers in each lung
Walls contain elastic fibres- expand during inhalation and recoil during expiration
How do the cells lining the trachea and bronchus protect the alveoli from damage?
Cells produce mucus that traps particles of dirt.
Cilia on cells move debris up trachea and into stomach.
What is the difference between inspiration and expiration?
Inspiration = movement of air
Expiration = movement of air out of the lungs
What happens as a result of the external intercoastal muscles contracting?
Inspiration
What happens as a result of the internal intercoastal muscles contracting?
Leads to FORCED expiration
What is pulmonary ventilation?
Total volume of air that is moved into the lungs during one minute.
What is tidal volume?
The volume of air that moves into and out of the lungs with each breath
When does the diaphragm contract and relax?
Contract= inspiration (flattens bringing lungs with it)
Relax= expiration (moves up)
What must be maintained to ensure a constant supply of oxygen to the body?
A diffusion gradient at the alveolar surface
Why is the diffusion of gases between the alveoli and blood very rapid?
- Red blood cells are slowed as they pass through pulmonary capillaries (more diffusion)
- Walls of alveoli and capillaries are very thin
- Large surface area
- Concentration gradient maintained by blood flow through capillaries
How does each pulmonary capillary being very narrow contribute to the efficiency of gas exchange?
Red blood cells are flattered against the walls of capillaries to enable them to pass through.
Slows them down, increasing time for gas exchange and reducing diffusion pathway, increasing rate of diffusion.
What risk factors increase the probability of someone suffering from lung disease?
- Smoking
- Air pollution
- Genetic make-up
- Infections
- Occupation
What are the effects of lung diseases on gas exchange?
- Reduced rate of gas exchange
- Less oxygen able to diffuse into bloodstream, body cells receive less oxygen- rate of aerobic respiration is reduced.
- Less energy is released so sufferers often feel tired and weak.
What are the main effects on gas exchange when someone has asthma?
Airways constrict
Concentration gradient decreases
What are the main effects on gas exchange when someone has emphysema?
- Alveoli walls break down
- Reduced surface area of alveoli
- Decreasing gas exchange
What are the main effects on gas exchange when someone has fibrosis?
Greater diffusion distance because scar tissue around alveoli
What is the gas exchange surface in a dicotyledonous leaf?
Surface of the mesophyll cell
What is a xerophyte?
A plant that is adapted so it does not need much water
What are some of the features found in a xerophyte?
Reduced SA:V to reduce water loss
Thick waxy cuticle to reduce water evaporation
Leaves reduced to spines to reduce SA for water loss
Deep roots to obtain water from deep sources
Wide roots to obtain water when it rains
Stomata that open at night reducing water loss
Rolling of leaves to trap humid air around stomata
How can capillaries running over the surface of the alveoli improve efficiency of gaseous exchange?
Delivers CO2 to be removed from the body, carries oxygen away from alveoli
Short diffusion distance
How does the lungs being surrounded by the diaphragm and intercostal muscles improve the efficiency of gaseous exchange?
Ventilation
Supply of oxygen - removal of CO2
What is the function of the goblet cells in the bronchus?
To secrete mucus
Why do the walls of the alveoli contain elastic fibres?
To increase lung volume
So they can contract and re-coil
What would be the effect of a loss of elasticity on the gaseous exchange system?
Less surface area for exchange
Less diffusion distance
Less CO2 diffuses out
How does covering a leaf in epidermal hairs help xerophytes survive in their habitat?
Hairs trap water vapour, reduce water potential gradient
