exchange and transport systems A Flashcards
how does an organism’s size relate to their surface area to volume ratio?
the larger the organism, the lower the surface area to volume ratio.
Relationship between SA:V (and thus the size of an organism) and metabolic rate
-Rate of heat loss / heat lost per unit body mass increases as SA:V increases
-i.e. more heat lost per unit body mass in smaller animals with a high SA:V
-So they need a higher metabolic rate / faster respiration
-To generate enough heat to maintain a constant body temperature i.e. replace lost heat
Exchange and transport in unicellular organisms
-can rely on diffusion to exchange substances
-short diffusion pathway from cell surface to centre of cell
-larger SA;V ratio
-microvilli can increase SA;V ratio further
exchange and transport in multicellular organisms
-need exchange and transport systems
-long diffusion pathway from body surface to centre of body so diffusion would take much too long
-smaller SA:V ratio so cannot exchange enough substances through surface
relationship between body shape/size and heat exchange
-body shape can increase SA:V ratio (large ears) or decrease SA:V ratio (round shape)
-smaller organisms have faster heat loss through their surface because of higher SA:V ratio
what is a metabolic rate and how is it measured
=amount of energy used up by an organism in a given amount of time
-often measured by measuring oxygen uptake
why do active organisms have a higher metabolic rate
-use up more ATP in a given amount of time
-need more oxygen per unit of body mass
a small animal with a higher SA:V have ……… heat loss per gram of body mass, so have a …… rate of metabolism which…… heat
1.faster
2.faster
3.releases
Adaptations of gas exchange surfaces: across the body surface of a single-celled organism
-Thin, flat shape and large surface area to volume ratio
- Short diffusion distance to all parts of cell for rapid diffusion eg. of O2 / CO
why cant insects use their bodies as an exchange surface?
have a waterproof chitin exoskeleton and a small SA:V ratio in order to conserve water
Describe the tracheal system of an insect
- Spiracles = pores on surface that can open / close to allow diffusion
- Tracheae = large tubes full of air that allow diffusion
- Tracheoles = smaller branches from tracheae, permeable to allow gas exchange with cells
adaptations for gas exchange ( tracheal system of an insect)
-Tracheoles have thin walls =Short diffusion distance to cells
-High numbers of highly branched tracheoles=Short diffusion distance to cells and large SA for gas exchange
-Tracheae provide tubes full of air=Fast diffusion
-Fluid in end of tracheoles moves out during exercise = larger SA
-Contraction of abdominal muscles changes pressure in body causing air to move in / out=Maintains concentration gradient for diffusion of O2 / CO2
how is the tracheal system of an insect adapted to reduce water loss
-Thick waxy exoskeleton=Increases diffusion distance so less evaporation
-Spiracles can open & close=Open to allow oxygen in and carbon dioxide out. Close to reduce water loss by evaporation
-Tiny hairs around spiracles=Trap most air → reduce water potential gradient → less water lost by evaporation
explain the process of gas exchange in insects
-gases move in and out of the tracheae through the spiracles
-diffusion gradient allows oxygen to diffuse into the body tissue while waste CO2 diffuses out
-contraction of muscles in the tracheae allows mass movement of air in and out
why cant fish use their bodies as an exchange surface
have a waterproof,impermeable outer membrane and a small SA:V ratio
what are the adaptations for gas exchange in gills of fish
-Each gill made of many filaments covered with many lamellae =Increase surface area for diffusion
-Thin lamellae wall =Short diffusion distance between water / blood
-Lamellae have a large number of capillaries=Remove O2 and bring CO2 quickly → maintains concentration gradient
counter current exchange system maximise oxygen absorbed by the fish, what happens in counter current flow
- Blood and water flow in opposite directions
through/over lamellae - So oxygen concentration always higher in water than blood near
- So maintains a concentration gradient of O2 between water and blood
- For diffusion along whole length of lamellae
why cant water and blood flow in the same direction
equilibrium would be reached, so oxygen wouldn’t diffuse
into blood along the whole gill plate.
adaptations for gas exchange of dicotyledonous plants
-Many stomata=Large surface area for gas exchange (when open) but can close to reduce transpiration
-Spongy mesophyll cells contain air spaces=Large surface area for gases to diffuse through
-thin= short diffusion pathway
what is a xerophyte
a plant adapted to live in very dry,windy,warm conditions
adaptations of xerophytic plants to reduce water loss
*thicker waxy cuticle = Increases diffusion distance so less evaporation
*Sunken stomata in pits,Rolled leaves,Hairs=
-‘Trap’ water vapour / protect stomata from wind
- So water potential gradient between leaf and air decreased
- So less evaporation
*Spines / needles=Reduces surface area to volume ratio
what is the structure of the lungs
*Trachea → windpipe from mouth
* Bronchi → branch off from trachea, one bronchus to each lung
* Bronchioles → branch off from bronchi, smaller tubes
* Alveoli → tiny air sacs at the end of bronchioles where gas
exchange occurs
* Surrounded by the ribcage and intercostal muscles
how are lungs adapted for gas exchange
-Many alveoli / capillaries=Large surface area
-Alveoli / capillary walls are thin=Short diffusion distance
-Ventilation / circulation=Maintains concentration gradient
The essential features of the alveolar epithelium as a surface over which gas exchange takes place
- Thin / flattened cells / one cell thick → short diffusion distance
- Folded → large surface area
- Permeable → allows diffusion of oxygen and carbon dioxide
- Moist → gases can dissolve
- Good blood supply from network of capillaries → maintains concentration gradient
