EXCHANGE Flashcards
Describe gas exchange in single called organisms
small so have a large surface area to volume ratio
Oxygen is absorbed and diffuses across the body surface
Carbon dioxide from respiration diffuses out across the body surface
There is no cell wall only a cell membrane
Why do insects need to conserve water
They lose water easily by evaporation causing dehydration so they need to conserve water
They need to have a balance between exchange of respiratory gases and conserving water loss
Role of trachea (insects)
Internal network of tubes important for gas exchange
Supported by strengthened rings that prevent them from collapsing
Divide into smaller dead end tubes called tracheoles
Role of tracheoles
Smaller dead end tubes
Extend all throughout the bodily tissues so that atmospheric air can be transported to all living tissues in the insect
What are the two ways respiratory gases can move in and out of the tracheal system
- ALONG A DIFFUSION GRADIENT = Cells respire and use of O2 so conc of O2 towards end of tracheoles falls. This creates a diffusion gradient causing oxygen from the atmosphere to diffuse across the trachea and tracheoles and into the cell. During respiration CO2 is produced and this creates a diffusion gradient in the opposite direction. Therefore CO2 from the cell diffuses out and across the tracheoles and trachea into the atmosphere
- MASS TRANSPORT = Contraction of muscles in the insect caused squeezing of trachea. This results in mass movements of air in and out therefore speeding up the exchange of respiratory gases in the insect
Role of spiracles
Tiny spores that control when gases enter and leave
Valves are used to open and close the spiracles
When open water vapour can evaporate from the insect
Usually kept closed to prevent water loss
Limitations of the tracheal system
Relies heavily on diffusion
- limitation as its means the diffusion pathway has to be short resulting in insects being of a small size
Adaptation of tracheal system
Tracheoles have thin walls = short diffusion distance for gases to cells
Tracheoles are highly branched = increases surface area for gas exchange
Muscles can pump body forcing air in and out = maintains conc gradient for gases
Spiracles can open and close = prevents water loss
Structure of fish gills
Gills are made up of gill filaments which are stacked up in a pile
The gill filaments are attached to the gill bar which is made of cartilage
At right angles to the gill filaments are the gill lamellae which increase the surface area of the gills
What is the site of gas exchange in fish
Gill lamellae
Explain the countercurrent exchange system
Water and blood must flow in opposite direction for maximum gas exchange to take place
O2 rich blood meets with water that also has a high concentration of O2
O2 deficient blood meets with water that has had most of its oxygen removed so that diffusion from oxygen to water takes place
Ensures that no equilibrium is reached and that a diffusion gradient is maintained over the whole length of the gill lamellae
Adaptation of fish for gas exchange
Thin walls of epithelium = short diffusion distance for gases from water to blood
Large SA:V ratio = due to large amount of gill filaments and lamellae
Countercurrent flow = Maintains concentration gradient of whole length of gill lamellae
What do plants need for photosynthesis
Adequate amount of CO2
Describe the structure of a leaf
Waxy cuticle = surface run off
Upper epidermis = layer of tightly packed cells acts as like a protection barrier
Palisade mesophyll = contain chloroplast
Spongy mesophyll = contains air sacs
Stomata = pores on the underside of cell which allow air to enter
Guard cells = control the open and closing of stomata
Lower epidermis = layer of tightly packed cells
Mechanism in a leaf
- Turgid guard cells remain open so that air can enter the stomata
- Air sacs in spongy mesophyll allows for rapid diffusion of CO2 into cells
= this CO2 is then used in chloroplast for respiration and therefore maintains the concentration gradient - No ventilation due to presence of stomata creating a short diffusion pathway
How and insects lose water and what adaptations do they have to limit this
They lose water as it easily evaporates from their bodily surfaces and causes them to become dehydrated easily
The adaptation they have are:
1. Spiracles
2. Small surface area to volume ratio to minimise the area over which water is lost
3. Exoskeleton is covered in a waterproof cuticle
Why can’t plants have a small surface area to volume ratio
Because they photosynthesise which requires a large surface area to volume ratio
What adaptions to terrestrial plants have to reduce water loss
They have a waterproof covering over parts of the leaf and stomata
What is a xerophyte
A plant that is that adapted to living in areas where water supply is short
Adaptation of xerophytes
Thick cuticle = reduces water loss
Rolling leaves = protects the lower epidermis and traps still air. This region becomes saturated with water vapour and has a high water potential
Stomata in pits of leaves = trap still air reducing water potential gradient
Reduced surface area to volume ratio in some parts of the leaves minimises water loss
Why is the volume of O2 absorbed and CO2 removed large in mammals
They’re relatively large organisms with a large amount of living cells
Maintain a high body temperature which is related due to high metabolic and respiratory rates
Why do mammals have lungs
To ensure efficient gas exchange between air and blood
