Gas exchange Flashcards
What are gas exchange surfaces?
Gas exchange
Boundaires between the outside environment and the internal environment of an organism where gas exchange occurs
Organisms need oxygen and CO2 to diffuse across as quickly as possible
How are most gas exchange surfaces adapted to increase rate of diffusion?
Gas exchange
- Large surface area
- Thin - provides short diffusion pathway
- Organism also maintains steep concentrayion gradient of gases across exchange surface
How are single-celled organisms adapted for gas exchange?
Gas exchange
Large surface area, thin surface and short diffusion pathway
No need for specialised gas exchange system
How are fish adapted for gas exchange?
Gas exchange
Gill structure and Counter current system
Structure of gills
Gas exchange
Water, containing oxygen, enters fish through mouth and out through gills
Each gill made from thin plates called gill filaments - large SA
Gill filaments are covered in tiny structures called lamellae - increase SA even more
Lamellae have lots of blood capillaries and thin surface to speed up diffusion
Counter-current system
Gas exchange
In gills, blood flows through lamellae in one direction and water flows over them in opposite
Means H2O with high oxygen conc always flows next to blood with a lower conc of oxygen
Steep conc grad is maintained between H2O and blood - as much oxygen as possible diffuses from H2O to blood
How are dicotyledonous plants adapted for gas exchange?
Gas exchange
Plants need CO2 for photosynthesis which produces O2 as waste
They need O2 for respiration, which produces O2 waste
Main gas exchange surface is surface of mesophyll cells in leaf - have large SA
Mesophyll cells are inside leaf - gases move in and out through stomata
Stomata can open to allow gas exchange and close if losing too much water
Guard cells control opening and closing of stomata
How are insects adapted for gas exchange?
Gas exchange
Terrestrial insects have trachae
Air moves through pores on surface called spiracles
Oxygen travels down conc grad toward cells
Trachae branch off ito tracheoles, which have thin, permeable walls and go to individual cells
Oxygen diffuses directly into respiring cells
CO2 from cells moves down con grad toward spiracles and released
Insects use rhythmic abdominal movements to move air in and out of spiracles
How have insects adapted to control water loss?
Gas exchange
If they are losing too much, the close spiracles using muscles
Also have waterproof, waxy cuticle all over body and tiny hairs around spiracles, which reduces evaportation
How have plants adapted to control water loss?
Gas exchange
Stomata are usually open during day to allow gaseous exchange
Water enter guard cells, making them turgid, which opens stomatal pore
If plant starts to get dehydrated, the guard cells lose water and become flaccid, closing the pore
How are xerophytes adapted to warm, dry or windy habitats?
Stomata sunk in to trap water vapour, reducing con grad of water between leaf and air - reduces evaporation from leaf
A layer of ‘hairs’ on epidermis to trap water vapour around the stomata
Curled leaves with stomata inside, protecting them fro, wind (wind increases rate of diffusion and evaporation)
Reduced number of stomata, so there are fewer places for water to escape
Thicker waxy, waterproof cuticles on leaves and stems to reduce evaporation
