SA:V and gas exchange pmt flashcards
how does an organisms size relates to their surface area to volume ratio
the larger the organism , the lower the surface area to volume ratio
how does an organisms surface area to volume ratio relate to their metabolic rate
the lower the surface area to volume ratio, the lower the metabolic rate
how might a large organism adapt to compensate for its small surface are to volume ratio
changes that increase SA example folding , body parts become larger
elephants ear, elongating shape
developing a specialised gas exchange surface
why do multicellular organisms require specialised gas exchange surfaces
their smaller surface are to volume ratio means the distance that needs to be crossed is larger and substances cannot easily enter the cells as in a single-celled organisms
name three features of an efficient gas exchange surface.
1)large surface are eg folded membranes in mitchocondria
2)thin/short distance eg wall of capillaries
3)steep concentration gradient, maintained by blood supply or ventilation eg alveoli
why can’t insects use their bodies as an exchange surfaces
they have a waterproof chitin exoskeleton and a small surface area to volume ratio in order to conserve water
name and describe the three main features of an insects gas transport system
spiracles=holes on the body surface which may be opened or closed by a valve for gas or water exchange
-trachea=large tubes extending through all body tissues, supported by rings to prevent collapse
-tracheoles=smaller branches dividing off the tracheae
explain the process of gas exchange in insects
-gases move in and out of the tracheae through the spiracles
- a diffusion gradient allows oxygen to diffuse into the body tissue while waste CO2 diffuse out
-contraction of muscles in the tracheae allows mass movement of air in and out.
why can’t fish use their bodies as an exchange surfaces
they have a waterproof, impermeable outer membrane and a small SA:volume
name and describe the two main features of a fish gas transport system
gills=located within the body, supported by arches, along which are multiple projections of gill filaments, which are stacked up in piles
lamellae=at right angles to the gill filaments , give an increased SA.Blood and water flow across them in opposite directions(countercurrent exchange system)
explain the process of gas exchange in fish
the fish opens its mouth to enable the water to flow in, then closes its mouth to increase the pressure.
-the water passes over the lamellae, and the oxygen diffuses into the bloodstream
-waste CO2 diffuses into the water and flows back out the gills
how does the countercurrent exchange system maximise oxygen absorbed by the fish
maintains a steep concentration gradients water is always next to blood of a lower oxygen concentration.
-keeps rate of diffusion constant along the whole length of gill enabling 80% of available oxygen to be absorbed
name and describe three adaptions of a leaf that allow efficient gas exchange
1)thin and flat to provide short diffusion pathway and large SA:Volume ratio
2)many minute pores in the underside of the leaf(stomata) allow gases to easily enter
3)air spaces in the mesophyll allow gases to move around the leaf, facilitating photosysnthesis
how do plants limit their water loss while still allowing gases to be exchanged
stomata regulated by guard cells which allows them to open and close as needed . most stay closed to prevent water loss while some open to let oxygen in.
describe the pathway taken by air as it enters the mammalian gaseous exchange system.
nasal cavity to trachea to bronchi to bronchioles to alveoli
