biology

what happens when size of an organsim increases

this decreases the surface area to volume ratio this affects biological process such as gas exchange and nutrition

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what does decrease in surface area to volume ratio mean

means that less heat ius lost to the enviroment this explains large round organsims in cold climates and organsims in hot climates have adapations to increase heat loss such as large ear in elephant

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gaseous exchange in small organsims

respiratory gases have a short distance to travel so can be absrobed by diffusion alone

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explain gaseous exchange system in insects

insects have a intricate network of tubes known as tracheal system through which they absorb oxgen and remove carbon dioixde.

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explain external surfaces of insects

lined with cuticle to prevent water loss cuticle impermeable to respiratory gases so there are holes in exokeleton known as spiracles theyre opened and closed by valves in response to respiraory demand

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after air moves into spiracles into trachea what happens

air enters the trachea which is lined with chitin thus impermeable these branch of into smaller tubes called trachioles which are permeable the gases diffuse through these and into the cells

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how is rate of difusion incresed in tracheoles

there are many tracheoles which increase surface area there walls are thin for minimal diffusion distance also in times of high respiratory demand fluid in trachioles retract to further decrease diffusion distance

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explain gas exhange in bony fish

bony fish have gills which are adapted to removing oxygen from water whereit is at a lower and more variable concentraton than air rarely higher than 0.8

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adaptations for diffusion in fish

fish have 4 pairs of gill arches which support gillfilaments these are divided into lammela which increase surface area surface area is further increased by projecting gill plates

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explain counter current mechansim

maintains a concentration gradient across the gill water moves across the gill i theopposite direction to the flow of blood so bloodwith highest oxgen contents lines up with water with highestoxygen content

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diffusion in counter current mechansim

there is always higher concentration of water than in blood directly beeath it

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howis diffusion efficient in counter currentmechansim

effeicent circulation and ventilation help to maintain concentration gradient.blood supply is constantly replenished and the operculum a bony flap pumps bloodover the gills gillplates of thin are very thin which reduce diffusion distance

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