UNIT 3 (topic 2) gas exchange in insects, plants and fish Flashcards
what are the four features to ensure a good rate of diffusion
- large SA:V ratio - in contact with the environment
- short diffusion pathway - less travelling for molecules
- movement of environmental/ internal medium - maintains concentration gradient
- permeable - allow the exchange of materials
how does an exoskeleton (on insects) reduce water loss
- prevents evaporation
- gas exchange system located inside the body
what adaptation do insects have to perform gas exchange
pores in the cuticle known as spiracles - valved structures that can open and close to regulate air flow
spiracles connect to air-filled tubes (tracheae) which connect to smaller tubes (tracheoles) which terminates muscle fibres
describe abdominal pumping and how it speeds up gas exchange in insects
- contract muscles in the abdomen
- decreases volume of the tracheoles and increases pressure
- forces out stale air faster than by diffusion alone
describe the process of gas exchange for fish
- mouth opens, floor of buccal cavity lowers and opercula are closed
- pressure in the buccal cavity decreases and water is drawn into the mouth (down the pressure gradient) into the buccal cavity
- mouth closes, opercula opens and the floor of the buccal cavity raises increasing the pressure
- water flows from buccal cavity across the gills through the opercula
how are fish adapted for gas exchange (4)
- lamellae increases SA
- have permeable membranes
- lots of capillaries to increase blood flow and maintain conc. gradient
- thin flattened cells - short diffusion pathway
why is parallel flow insufficient at absorbing oxygen and what is sufficient
- equilibrium occurs half way meaning only 50% is diffused
- counter current flow allows water and blood to flow in opposite directions across lamellae
- always a concentration gradient
what is the symbol equation for photosynthesis
6CO2 + 6H20 ——> C6H1206 + 6O2
what is the symbol equation for respiration
C6H12O6 + 6O2 ——> 6CO2 + 6H2O
how does gas exchange occur in plants due to time of day
in daylight - guard cells take up water by osmosis and become turgid - causes them to open the stomata
in the dark - guard cells lose water, become flaccid and close stomata
how do leaves keep a large SA
air spaces in mesophyll and a large number of leaves
what is a xerophyte
collective name given to plants that are swollen and rubbery - cacti, aloe vera, succulents
how do xerophytes respond to water content
via osmosis - open when there is high concentration inside the leaf and closes when there is a low concentration in the leaf
why is the adaption of chitin waxy cuticles good for xerophytes
waterproof layer - water finds it difficult to pass
why is the adaptions of rolled leaves, stomata in pits or grooves, and hairy leaves good for gas exchange in xerophytes
- traps air inside = air takes up moisture
- keeps water potential high outside the leaf
- osmotic gradient is reduced
- less water lost through the stomata
