Gas Exchange Flashcards
what do single celled organisms do?
- absorb and release gases by diffusion through their cell-surface membrane
what adaptations do single-celled organisms have?
- relatively large surface area
- thin surface
- short diffusion pathway
why do fish need to have a specialised gas exchange surface?
- lower concentration of oxygen in water than in air
what is the function of the gills?
water containing oxygen enters the fish through its mouth and passes out the mouth through the gills
what is each gill made of?
- lots of thin plates called gill filaments
why is it a good thing to have gill filaments?
- there are many of them which gives a large surface area for exchange of gases = increases the rate of diffusion
what are the gill filaments covered in?
- tiny structures called lamellae
why is it good to have lamellae?
increases the surface area
how are lamellae adapted for diffusion?
- lots of blood capillaries = ventilation
- thin surface layer of cells = thin diffusion pathway
what is the counter-current system?
- in the gills of fish water and blood flow in opposite directions through the lamellae
what does the counter-current system enable?
- a concentration gradient of oxygen to be maintained across the whole length of the lamella
why is it good to have a counter current system?
- ensures that as much oxygen can diffuse from the water into the blood
- oxygen can diffuse across the whole length of the lamellae
what concentration does blood enter the lamella in?
low concentration of oxygen
what are the adaptations of fish in gas exchange?
- gills
- gill lamellae
- gill filaments
- counter current principle
what is the main gas exchange surface in the leaf?
mesophyll cells
how are mesophyll cells adapted for gas exchange?
they have a large surface area
where is the mesophyll cell?
inside the leaf
how do gases move in and out the epidermis?
pores called stomata
what do stomatas do?
- open to allow the exchange of gases
- close to reduce water loss
what controls the opening and closing of stomata?
guard cells
how are the leaves of dicotyledonous plants adapted for gas exchange?
- mesophyll
- stomata
what do the tracheae branch off into?
tracheoles
how does air move into the tracheae of an insect?
- pores on the surface of tracheae called spiracles
what does the gas exchange surface of an insect look like?
- spiracles
- tracheae
- tracheoles
what does the tracheae branch off into?
- smaller tracheoles which have thin, permeable walls
what system do insects have?
tracheal system (tracheae, tracheoles and spiracles)
how can insects control the loss of water?
- open and closing their spiracles using muscles
- waterproof, waxy cuticle
- tiny hairs around spiracles
= reduce evaporation
what are xerophytes?
plants which are adapted for life in warm, dray or windy habitats
how are xerophytic plants adapted to reduce water loss(5)?
- stomata sunk in pits
- layer of hairs on the epidermis
- curled leaves
- reduced number of stomata
- thicker waxy, waterproof cuticles
how is stomata sunk in pits advantageous for xerophytic plants?
- trap water vapour
- reducing concentration gradient of water between leaf and air
- reduces evaporation of water from the leaf
how is layer of hairs advantageous for xerophytic plants?
- trap water vapour around the stomata
how are curled leaves with the stomata inside advantageous for xerophytic plants?
- protects them from the wind as wind increases rate of diffusion and evaporation
how is a reduced number of stomata advantageous for xerophytic plants?
- fewer areas for the water to escape from
how is a thicker waxy, waterproof cuticles advantageous for xerophytic plants?
- on leaves and stem to reduce evaporation
what is an adaptation of the tracheae?
- provide tubes full of air so fast diffusion
