SECTION 3 Flashcards
AS THE SIZE OF AN organism gets bigger, what happens to the sa:vol ratio.
decreases (volume increases at a faster rate then SA, when an organism gets bigger.)`
how easy exchange of substances takes place is dependent on SA:Vol ratio. the amount of material an organism needs to exchange depends on it…..
how much it can exchange depends on it ….
the amount of material an organism needs to exchange depends on its volume
how much it can exchange (through its surface) depends on its SA.
as the amount of material an organism needs to exchange increases by a lot, the amount of material it can exchange through its surface ….
increases by only a little
what happens if the metabolic rates exceeds the rate of exchange of vital materials and wastes due to a too low SA:VOL ratio.
the cell/organism will die.
single-celled organisms have what
a very large SA: vol ratio (compared to large multicellular organims)
why is the rate of diffusion fast in a single-celled organism
short diffusion distance (small distances the substances have to travel)
the SA:VOL RATIO OF MULTICELLULAR ORGANISMS is too low. what does thie mean in terms of exchange of substances
meaning the organism cannot exchange enough substances to supply a large volume of organism through a relatively small outer surface. (diffusion distances are too great)
linking to F7, larger organisms therefore have evolved exchange surfaces and transport systems to meet the exchange of substances demands of the cell, these systems have what features to help them maintain transport into and out of the organism.
large sa
good blood supply —-> to maintain conc gradient
thin membrane
(ventilation)
all this helps maintain a high rate of transport into and out of the organism
what does the rate of heat loss depend on?
SA:VOL RATIO
LARGE SA: VOL RATIO MEANS WHAT ABOUT HEAT LOSS, AND hence what does this to do to the metabolic reaction and for what reason
large SA: vol ratio ( eg a mouse) = more heat is lost to the surroundings. therefore metabolic rate has to increase to release heat from aerobic respiration to stay warm.
on the contrary to F10, animals ( eg, elephants do not have sweat glands hence have large ears with a large surface area, to release more heat energy to the surroundngs, helping to regulate/cool their body temp) in hot environments may have adaptations to increase surface area, for what purpose?
to lose more heat to stay cool.
how are single celled organisms adapted for efficient gas exchange by diffusion. (and state why they dont need a gas exchange system)
they have a large SA:vol ratio
they have a thin membrane for short diffusion distance, therefore gas exchange can take place by diffusion across the surface of the single-celled organisms, hence no gas exchange system is needed.
gas exchange in insects rely on what system?
the tracheal system.
what is the tracheal system and how does it work to allow gas exchange
series of tubes that supply respiring cells with o2 directly.
by pumping the abdomen, air is drawn in and out of the tracheae, which helps maintain a conc gradient for the diffusion of oxygen and carbon dioxide into and out of respiring cells.
Air moves into the tracheae through pores on the surface of the insect called spiracles.
oxygen diffuses down a conc gradient, towards the respiring cells.
the tracheae branch off into tracheoles, which have thin, permeable walls that border respiring cells
oxygen then diffuses from the tracheoles directly to the respiring cells.
co2 diffuses out of the respiring cells towards the spiracles, down its conc gradient, to be released into the atmosphere.
how do insects minimise water loss
1) spiracles can be closed to prevent water loss
2) hair around spiracles trap humid air, creating a low conc gradient of water vapour betwen inside the insect and outside the spiracles, hence reducing the rate of diffusion of water vapour out of the spiracles, and therefore reducing the risk of dessication.
3) there are air sacs around the tracheae to provide an extra supply of oyxgen if the spiracles have to be closed for a longer period of time
the drying out of a livigng organism is known as …
dessication
why cant insects get bigger
because the tracheal system wouldnt be able to meet the o2 demand (as bigger organism=more cells, and more cells = more o2 needed), and it wouldnt be able to meet the o2 demand because the diffusion distances would be too big, hence it would take far too long for o2 to reach the respiring cells by diffusion.
why in an aquatic env is an efficient gas exchange system vital? and what overcomes these problems for fish for eg,
because much lower conc of o2 in water than in air
and because diffusion of o2 and co2 is much slower.
THEREFORE AS RESULT, FISH HAVE GILLS - WHICH ARE GAS EXCHANGE ORGANS ADAPTED TO OVERCOMIGN THESE PROBLEMS.
fish open their mouths and allow the water to flow through the gills, and out via what?
the operculum (gill cover)
how are gills adapted to efficient gas exchange?
https://merchanttaylorsschools-my.sharepoint.com/:w:/g/personal/tofoma_merchanttaylors_com/ES-rlz9TkSVIhD5P8BNhrsgBjjuokKpNzL3SmSSFJoywSQ?e=kGP5Os
whats the counter-current system in fish?
https://merchanttaylorsschools-my.sharepoint.com/:w:/g/personal/tofoma_merchanttaylors_com/EQcI26y7GcVEpTx9rrKjV9IBbDzjWDZP4ZmsFNsH3-f0xg?e=5FTDKl
most photosynthesis takes place where and why?
most photosynthesis takes place in teh palisade mesophyll cells (as they receive the most sunlight), because they contain lots of chloroplast.
upper epidermis of leaves function
protects internal tissues from mechanical damage + invasion of bacteria and fungi.
how are leaves adapted to effficient gas exchange
stomata allow diffusion of gases in and out of the leaf. - many stomata means cells are closer together, hence creating a short diffusion distance for gases diffusing to and from cells.
air spaces allow fast diffusion of gases within the leaf directly to and from cells
the large surface area of leaf, means there is an increased rate of diffusion.
