3.1 Adaptations for Gas Exchange

process by which oxygen reaches the cells and carbon dioxide is removed from them

the process of moving the respiratory medium (air or water) over the respiratory surface to maintain a concentration gradient

series of chemical reactions that results in the release of energy in the form of ATP

a molecules which increases the oxygen carrying capacity of the blood e.g haemoglobin

a system of branched chitin lined air tubes in insects

site of gas exchange in insects

holes in an insects exoskeleton which can open and close like valves to allow exchange of gases and reduce water loss which can lead to dehydration

site of gas exchange in fish

site of gas exchange in mammals

the larger the organism the longer the diffusion pathway so the longer it takes for gases to reach the centre of the cell

amoeba

extremely large SA:V occurs across whole cell membrane permeable membrane no specialised system required diffusion sufficient to meet oxygen requirements

flatworm

increased SA:V due to flattened shape short diffusion pathway no specialised system diffusion across membrane sufficient enough to meet oxygen requirements

earthworm

tubular shape live in damp environments secret mucus to keep cells moist for gases to dissolve elongated shape for large SA:V blood vessels close to surface for easy diffusion blood circulation maintains a concentration gradient contain haemoglobin to carry oxygen to cells

• small SA:V • diffusion insufficient • more metabolically active • long diffusion path • method of circulation to distribute gases • animals with toughened body surface need internal exchange surfaces

• moist so gases can dissolve • thin so there is short diffusion path • permeable so gases can diffuse easily • large SA:V so more room for diffusiont

do not use blood to transport gases. air diffuses into the insect through holes in the exoskeleton called spiracles. the spiracles leas to branched air tubes lined with chitin called trachea. the trachea branch into tracheoles.

they are filled with fluid to keep the gas exchange interface moist so gases can easily dissolve

• oxygen supplied directly to tissues • no respiratory pigment needed • oxygen diffuses faster in air than blood • spiracles can close to reduce water loss and prevent dehydration

to reduce water loss to reduce heat loss protected by the ribcage or the exoskeleton in insects

gas exchange system where blood in the gill capillaries circulates in the same direction as water flowing over the gills

gas exchange system where blood in the gill capillaries circulates in the opposite direction to water flowing over the gills