3 Substance exchange- Gas exchange (animals/plants) Flashcards
Why do organisms need to exchange?
-To obtain substances from their environment to be used in processes in the cell (e.g. oxygen; respiration)
-Waste substances removed from cell (e.g. CO2) to not harm cell
How do single-celled organisms exchange?
-Can exchange gases/other substances using their cell membrane
-Rate of gas exchange increased by larger surface area to volume ratio; single-celled organisms adapt to increase this (e.g. wide, flat)
-Diffusion is rapid as substances only move across one cell-surface membrane
What are gas exchange surfaces?
Parts of the body that are specialised for gas exchange
What gas exchange system does an insect use + explain?
Tracheal system
A network of small tubes called tracheoles that carry oxygen around the body
It is the most efficient gas exchange system in animals
What are spiracles?
Openings on insect bodies which lie along the thorax and abdomen
-Gases (e.g. oxygen) diffuse through the spiracles, into the tracheoles
-Gases (e.g. CO2) also diffuse out of the spiracles
What is the gas exchange system in fish + describe?
Use a gas exchange system specialised for obtaining oxygen from water
Gils- filaments of thin tissue, highly branched & folded. Covered in lamellae which increase surface area. Create a large surface area for gas exchange
How does oxygen diffuse into the blood in fish?
Water flows through gills–> oxygen in water diffuses into bloodstream, this happens due to the counter-current system
What is the counter-current exchange system and what does it ensure?
The circulatory system of fish
Blood flows through lamellae in opposite direction of the flow of water through gills
Ensures steep concentration gradient between water and blood always
Where does gas exchange take place in a dicotyledonous plant + adaptations?
Mesophyll cells- site of photosynthesis located in middle layer of plant leaves
Have a large surface area to allow rapid exchange of CO2 and O2 with the environment
How does CO2 diffuse into plant leaves?
CO2 diffuses into plant leaves through stomata pores, on the underside of the leaf (epidermis)
What other role do stomata play (not diffusion)?
Controlling water
Guard cell on either side of stoma, open and close stomata to control water loss
Guard cells swell= stomata opens
What can happen to water during gas exchange?
Can be lost
This can be minimalised without sacrificing exchange rates through adaptations
What adaptations do insects have to prevent water loss?
Spiracles
-Terrestrial insects can close them to prevent water loss
-Have hairs; decrease water potential gradient between inside trachea and environment, decreases diffusion
Waxy cuticle
-On body, waterproof; prevents water loss
What conditions are xerophytic plants specialised to?
Dry habitats, where water availability is low
What adaptations do xerophytic plants have to prevent water loss?
-Fewer stomata, to avoid dehydration (when water is lost while stomata are open)
-Stomata sunk into pits in the epidermis; these trap moist air and decreases the water potential gradient between inside and outside of leaves to slow rate of diffusion of water out of the stomata
-Fine hairs covering epidermis; trap moist air and decrease rate of water loss, like prev
-Curled leaves; so stomata are sheltered from wind, which increase diffusion of water
-Waxy cuticle; waterproof, reduces evaporation of water
