surface area to volume ratio and gas exchange Flashcards
how does an organisms size relate to sa:v
larger organism means lower sa:v
how does an organisms sa:v relate to metabolic rate
smaller sa:v, higher metabolic rate
how might large organism adapt to compensate for its small sa:v
changes that increase surface area
larger body parts
elongating shape
developing specialised gas exchange surface
why do multicellular organisms require specialised gas exchange surfaces
their smaller surface area 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 organism
name three features of an efficient gas exchange surface
- large surface area
- short diffusion distance
- steep concentration gradient
why cant insects use their bodies as an exchange surface
they have a waterproof chitin exoskeleton and a small sa:v ratio in order to conserve water
name and describe the three main features of an insect’s gas transport system
- spiracles = holes on the body’s surface which may be opened or closed by a valve for gas or water exchange
- tracheae = large tubes extending through all body tissues, supported by rings to prevent collapse
- tracheoles = smaller branches diving off the tracheae
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
explain the process of gas exchange in insects
- gases move in and out of tracheae through spiracles
- a diffusion gradient allows oxygen to diffuse into 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
they have a waterproof, impermeable outer membrane and a small sa:v
two main features of fish gas transport
gills and lamellae
describe the gill
located within the body
supported by arches, along which are multiple projections of gill filaments, which are stacked up in piles
describe lamellae
at right angles to the gill filaments, give an increased surface area
blood and water flow across them in opposite directions
(COUNTERCURRENT SYSTEM)
explain the process of gas exchange in fish
- fish opens mouth to enable water to flow in, then closes mouth to increase pressure
- water passes over the lamellae, and the oxygen diffuses into the bloodstream
- waste CO2 diffuses into the water and flows back out of the gills
how does the countercurrent exchange system maximise oxygen absorbed by fish
maintains a steep concentration gradient, as water is always next to blood of a lower concentration
keeps rate of diffusion at constant and enables 80% of available oxygen to be absorbed
name and describe three adaptations of a leaf that allow efficient gas exchange
- thin and flat to provide short diffusion pathway and large sa:v
- many stomata allow gases easily enter
- air spaces in the mesophyll allow gases to move around leaf, facilitating photosynthesis
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
trachea
bronchi
bronchioles
alveoli
describe the function of the nasal cavity in the mammalian gaseous exchange system
a good blood supply warms and moistens the air entering the lungs
goblet cells in the membrane secrete mucus which traps dust and bacteria
describe the trachea and its function in the mammalian gaseous exchange system
- wide tube supported by C-shaped cartilage to keep the air passage open during pressure changes
- lined by ciliated epithelium cells which move mucus towards the throat to be swallowed, preventing lung infections
- carries air to the bronchi
describe the bronchi and their function in the mammalian gaseous exchange system
- like the tracheae they are supported by rings of cartilage and are lined by ciliated epithelium cells
- however they are narrower and there are two of them, one for each lung
- allow passages of air into the bronchioles
describe the bronchioles and their function in the mammalian gas exchange system
- narrower than bronchi
- do not need to be kept open by cartilage, therefore have only muscle and elastic fibres so that they can contract and relax easily during ventilation
- allow passage of air into alveoli
describe alveoli and their function in mammalian gas exchange system
- mini air sacs, lined with epithelium cells, site of gas exchange
- walls only one cell thick, covered with a network of capillaries, 300 million in each lung, all of which facilitates gas diffusion
explain the process of inspiration and the changes that occur throughout the thorax
- external intercostal muscles contract
- ribs up and out
- volume of thorax increases
- air pressure outside lungs is therefore higher than the air pressure inside, so air moves in to rebalance
explain the process of expiration and changes in thorax
- external intercostal relax
- ribs down and in
- diaphragm relaxes and domes upwards
- volume of thorax decreases
- air pressure inside lungs therefore higher than the air pressure outside, so air moves out to rebalance
what is tidal volume
volume of air we breathe in and out during each breath at rest
what is breathing rate
number of breaths per minute
