3) Organisms Exchange Substances With Their Environment Flashcards
- Exchange - Mass transport
why do larger organisms require exchange systems?
because they have a larger surface area to volume ratio and so cannot rely on simple diffusion
why can single-celled organisms rely only on diffusion for gas exchange?
because the diffusion pathway is short
give 3 feature of an efficient gas exchange surface
- large surface area
- thin
- good blood supply/ventilation
why is good blood supply/ventilation necessary for efficient gas exchange?
to maintain a steep concentration gradient
why can’t gases diffuse through fish’s skin?
they have an impermeable membrane that gases can’t diffuse through
describe the gas exchange surface of bony fish
- four pairs of gills, each supported by an arch
- along each arch, there are gill filaments with further projections on them, lamellae
how does the flow of blood and water across the lamellae aid gas exchange?
- blood and water flow across the lamellae in a counter-current direction (in opposite directions)
- this maintains a steep concentration gradient so maximum O₂ diffuses into the deoxygenated blood from the water and gas exchange occurs along the whole length of the lamellae
why can fish not survive very long out of water?
water flow holds the lamellae apart so out of water they stick together
describe the process of ventilation in fish
- fish opens its mouth and lowers buccal cavity floor, allowing water to flow in
- fish closes its mouth causing the buccal cavity floor to raise
- this increases pressure and forces water over the gill filaments by the difference in pressure between the mouth cavity and opercular cavity
what are tracheae?
microscopic air-filled tubes for gas exchange in insects
what are spiracles?
pores on insects’ surface which air moves through into the tracheae
what are tracheoles?
smaller tubes that branch of the tracheae which have thin, permeable walls and go to individual cells
what does the tracheal system allow insects to do in relation to oxygen transport?
oxygen diffuses directly into the respiring cells
how is carbon dioxide transported out of insects’ cells?
moves down concentration gradient towards spiracles to be released into the atmosphere
how do insects move air in and out of the spiracles?
by rhythmic abdominal movements
what is the main gas exchange surface in plants?
the surface of the mesophyll cells in the leaf
how do gases move in and out of a leaf?
through stomata in the epidermis
how are stomata adapted to control water loss and gas exchange?
they can open to allow gas exchange and close to prevent water loss
what controls the opening and closing of stomata?
guard cells
what adaptions do insects have to prevent water loss?
- can close spiracles using muscles
- waterproof waxy cuticle over body and tiny hairs around spiracles to reduce evapouration
what adaptations do plants have to prevent water loss?
if the plant becomes dehydrated the guard cells lose water and become flaccid, closing the pore
what are xerophytes?
plants are that adapted for life in warm, dry, or windy habitats where water loss is a problem
give five adaptations of xerophytes to minimise water loss
- stomata sunk in pits
- layer of hairs on the epidermis
- curled leaves with stomata inside
- fewer stomata
- waxy, waterproof cuticles on leaves and stems
explain how having stomata sunk in pits helps a xerophyte prevent water loss
traps moist air so reduces the water potential gradient between leaf and air
explain how having a layer of hairs on the epidermis helps a xerophyte prevent water loss
traps moist air around the stomata reducing the water potential gradient between the leaf and air
explain how having curled leaves with the stomata inside helps a xerophyte prevent water loss
protects the from wind - windy conditions would increase the rate of diffusion and evporation
explain how having fewer stomata helps a xerophyte prevent water loss
there are fewer places for water to leave
explain how having waxy, waterproof cuticles on leaves and stems helps a xerophyte prevent water loss
reduces evaporation
why is the volume of oxygen to be absorbed and the volume of carbon dioxide to be removed large in mammals?
- they are relatively large organisms with a large volume of respiring cells
- they maintain a high body temperature related to their high metabolic and respiratory rates
what is the site of gas exchange in mammals?
the lungs
what is the purpose of the ribcage?
to support and protect the lungs
what is the trachea?
flexible airway, supported by rings of cartilage
what are the tracheal walls made up of?
muscle lined with ciliated epithelium and goblet cells
what are the bronchi?
two divisions of the trachea, each leading to one lung
what is the role of external and internal intercostal muscles between ribs?
contract to raise and lower the ribcage
what is the purpose of the diaphragm?
separates the lungs from the abdomen
where in the lungs does gas exchange take place?
in the alveoli
how are the trachea and bronchi held open?
by c-shaped rings of cartilage on the walls
what is the inner lining of the trachea and bronchi composed of?
ciliated epithelium and goblet cells
what are the walls of the bronchioles made out of?
smooth muscle and elastic fibres
what adaptations do the bronchi have to prevent dirt particles travelling down?
mucus, secreted by goblet cells, traps dirt particles and cilia move the dirt-covered mucus towards the throat
what are the bronchioles?
series of branching divisions of the bronchi
what are the bronchiole walls made of? why?
- muscle
- allows them to constrict to control air flow in and out of the alveoli
what are the alveoli?
microscopic air-sacs at the end of bronchioles
state and explain three ways alveoli are adapted for gas exchange
- one cell thick (reduces diffusion pathway for gases)
- constant blood supply by capillaries (maintains steep concentration gradient)
- millions of alveoli (increases surface area for gas exchange)
what is the role of goblet cells?
secrete mucus to trap bacteria and dust
what is ventilation?
the flow of air in and out of the alveoli
describe the process of inspiration
- external intercostal muscles contract, internal intercostal muscles relax
- ribs move upwards
- diaphragm contracts and flattens
- volume in thorax increases, lowering the pressure
- pressure gradient between atm and inside lungs causes air to be forced into the lungs
describe the process of expiration
- internal intercostal muscles contract, external intercostal muscles relax
- ribs lower
- diaphragm relaxes and moves upwards
- this decreases volume inside the thorax, increasing pressure
- pressure gradient between atm and inside lungs forces air out of the lungs
what is a spirometer used to measure?
lung volume
what is vital capacity?
the maximum volume of air that can be inhaled or exhaled in a single breath
what is tidal volume?
the volume of air taken in at each breath when the body is at rest
what is breathing rate?
the number of breaths per minute
how can breathing rate be calculated from a spirometer trace?
counting the number of peaks or troughs in a minute
what is residual volume?
the volume of air that is always present in the lungs
what is digestion?
the hydrolysis of large biological molecules into smaller molecules which can be absorbed across cell membrane
what is the role of the oesophagus?
carries food from the mouth to the stomach
what is the role of the stomach?
- store and digest food, especially proteins
- has glands that secrete enzymes that digest proteins
what is the role of the ileum?
- further digests food by enzymes, produced by its walls and glands
- absorbs products of digestion into blood stream
how is the ileum adapted for absorption of products of digestion?
- walls folded into villi to increase surface area
- microvilli further increase surface area
- villi only one cell thick for short diffusion pathway
- continual flow of blood through maintains steep concentration gradient
what is the role of the large intestine?
absorbs water
what are the two stages of digestion?
- physical breakdown
- chemical breakdown
