organisms exchange with environment Flashcards
single celled organisms have a ?
short diffusion distance
multi-cellular organisms are large and that means they have a?
smaller SA:V
why cant animals and plants perform simple gas exchange?
-they have a large SA:V
-they’re multi-cellular
-they have an impermeable surface
= therefore they require specialised systems
why do fish have specialised gas exchange systems?
- multi-cellular
- smaller SA:V
- large diffusion distance
- high demand
- impermeable body surface
what is the structure of gills?
- gill filaments and lamellae = large surface area
- lamellae = = thin, short diffusion distance and permeable
- lamellae = thin, so there’s a lot of blood capillaries which means there’s a short distance between water and blood.
outline and explain the counter-current system in fish
- ventilation brings in pure water and circulation brings in deoxygenated blood
- water and blood pass over each other in opposite directions (counter-current flow)
- which maintain conc. gradient over the whole length of the gills.
in plants, what do the mesophyll cells allow to happen?
- they have a large surface area
- they allow gases to move in and out through pores called stomata in the epidermis
what do stomata do?
open and close to control water loss and gas exchange
what do guard cells do?
control the opening and closing of the stomata
explain gas exchange in insects
- they have openings in their body called spiracles
- spiracles open to allow gas exchange to happen and they close to prevent water loss
- spiracles connect to trachea
- oxygen diffuses down the conc. gradient
- trachea branches into tracheoles (which are thin permeable walls = oxygen can diffuse directly to respiring cells)
- Carbon dioxide goes down its conc gradient to the spiracles and gets released.
how are insects adapted to reduce water loss?
- spiracles can close
2. they have a waterproof, waxy cuticle on their body to reduce evaporation
briefly outline gas exchange in humans
- breathe in, air enters trachea
- trachea is split into 2 bronchi
- each bronchus, branches off into bronchioles which end in the alveoli (where gas exchange occurs)
ventilation consists of inspiration and expiration
where are the intercostal muscles located?
between ribs
describe the process of inspiration
- external intercostal muscles contract
- ribcage moves up and out
- diaphragm contracts (flattens)
- increases the volume in the chest and decreases in pressure
- air moves in
describe the process of expiration
- external intercostal muscles relax
- ribcage moves down and in
- diaphragm relaxes
- decreases the volume in the chest and increases in pressure
- air pushed out
