Topic 3 Organisms exchange substances. Surface area to volume ration + gas exchange Flashcards
(46 cards)
what is surface area of an organism
The surface area refers to the total area of the organism that is exposed to the external environment
what is volume of an organism
The volume refers to the total internal volume of the organism (total amount of space inside the organism)
How do you calculate the volume?
Volume= length xheight x width
or
area of face X length/depth
How do you calculate the suface area of a cube
area of face (lengthxlength) X 6 sides
Face X six sides
How do you calculate the surface area of a cuboid
surface area of rectangles
2x length xheight
2x length x height
2x height x width
total SA iis 2(lxh+lxw+hw)
How do you calculate the surface area of a cylinder
area of circle faces= πXR² X 2
area of rectangle= 2πXradius X height
What is the surface area to volume ratio
The relationship between the size of an organism or structure and its surface area to volume ratio, plays a significant role in the types of adaptations an organism will have
How does an organisms size relate to their surface area to volume ratio?
The larger the organisms, the lower the surface area to volume ratio therefore they cannot just diffuse substances across their surface they require adaptations to increase their surface area.
In the case of single celled organisms, the substances can easily enter the cell as the distance that needs to be crossed over is short. However, in multicellular organisms that distance is much larger due to a higher surface area to volume ratio. As a result of that, multicellular organisms required specialised exchange surfaces for efficient gas exchange of carbon dioxide and oxygen.
quick due to short diffusion pathway
-high SA: volume ratio
-oxygen and carbon dioxide can directly diffuse into cell through cell-surface membrane
Describe the surface area to volume ratio of small organisms (single cellular)
Small organisms have a very large surface area in comparison to their volume. (large SA:Vol ratio) Meaning that there is a big surface for exchange of substances but also there is a smaller distance from the outside of the organisms to the middle of it, as a result very small organisms can simple exchange substances across their surface via diffusion
Describe the surface area to volume ratio of larger organisms (multi cellular)
The larger an organism the smaller its surface area to volume ratio (longer diffusion pathway) Larger organisms will typically have a higher metabolic rate which demands efficent transport of waste out of cells and reactants into cells. as a result they are adapted to heko this be more efiicent
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What is the metabolic rate of an organism
The metabolic rate of an organism is the amount of energy expended by that organism within a given period of time
The basal metabolic rate (BMR) is the metabolic rate of an organism when at rest. The BMR is significantly lower than when an organism is actively moving
small organisms:-higher metabolic rate (to generate enough heat to stay warm)
-have larger SA:volume ratio = larger surface area for heat loss
larger organisms:low metabolic rate
-have smaller SA: volume = smaller surface area for heat loss
How does an organisms surface area to volume ratio relate to their metabolic rate
the lower the Sa:Vol ratio the lower the metabolic rate
adaptations to increase surface area to volume ratio
Villi and microvilli-absorbtion of digested food
alveoli and bronchioles- Gas exchange
Spiracles and tracheoles- gas exchange
gill filaments and lamelle-gas exchange
thin wide leaves-gas exchange
many capilliries-capillary network
Name three features of an efficient gas exchange surface
- Large surface area e.g folded membranes in mitrochondria
- Thin/short distance e.g wall of capillaries
- steep concentration gradient maintained by blood supply or ventiliation e.g alveoli
Why cant insects use their bodies an exchange surface
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’s surface which may be opened or closed by a valve for gas or water exchange. oxygen and carbon dioxide enter and leave via spiracles
Trachea-large tubes extending through all body tissues supported by rings of cartilage preventing collapse
tracheoles- smaller branches dividing off the trachea. deliver oxygen to all respiring cells.
How are insects adapted to limit water loss
water evaporates off the surface of terrestrial insects and the adaptations of gas exchange surfaces provide ideal conditions for evaporation.
1.insects have a small surface area to volume ratio where water can evaporate from
2. insects have a waterproof exoskeleton
3. spiracles where gases enter and water can evaporate from, can open and close to reduce water loss
-close spiracles by abdominal muscle contractions in ventillation
-spiracles close when insect is at rest = gaseous exchange reduced + reduced water loss
small SA: volume ratio to minimise surface area for water loss
-waterproof, waxy cuticle around exoskeleton = reduced water evaporation
-small hairs around spiracles retain some water = less water evporated
Describe gas exchange in insects
Oxygen enters the insect’s body via diffusion through small openings on the surface called spiracles.
From the spiracles, the oxygen moves into the tracheae, which are large tubes that carry oxygen deeper into the body. (diffusion because when cells respire they use up oxygen and produce carbon dioxide creating a concentration gradient from tracheoles to the atmosphere)
The tracheae branch into finer tubes called tracheoles, which spread throughout the insect’s body to deliver oxygen directly to the cells.
Oxygen diffuses from the tracheoles into the surrounding cells, where it is used in cellular respiration.
contraction of muscles in the trachea allows mass movement of air in and out
Adaptations to Facilitate Efficient Gas Exchange in insects
Active transport: In some insects, muscle contraction around the tracheae helps to move air and ensure a higher rate of gas exchange.
Thin walls of tracheoles: The walls are thin to facilitate diffusion of gases quickly and efficiently.
Large number of fine tracheoles-large surface area for diffusion (highly branched)
walls of tracheoles are thin and short distance between spiracles and tracheoles short diffusion pathway
use of oxygen and production of carbon dioxide sets up steep concentration gradient.
Three methods of moving gases in the tracheal system
Gas exchange via diffusion as when cells respire they use oxygen and produce carbon dioxide creating a conc gradient from tracheoles to the atmosphere.
The second method of gas exchange is mass transport, in which an insect contracts and relaxes their abodminal muscles to move gases on mass.
When the insects are in flight their cells start to respire anaerobically to produce lactate, lowering the water potential of the cells and therefore water moves from the tracheoles into the cells by osmosis. this decreases the volume in tracheoles and as a result more air from the atmosphere is drawn in .
How are insects adapted to limit water loss
Waterproof/impermeable chitin coat/layer on exoskeleton reduce water loss
spiracles can open/close so less water loss
hairs around spiracles reduce water loss
Why cant fish use their bodies as an exchange surface
They have waterproof impermeable outer membranes and a small surface area to volume ratio
Describe features of a fish’s gas transport system
Gills are made up of stacks of gill filaments.
each gill filament is covered in gill lamellae, position at right angles to the filament. creating a large surface area. Blood and water flow across them in opposite directions (counter current exchange system)
when the fish open their mouth water rushes in and over the gills and then out through a hole in the sides of their head
What is ficks law
Diffusion ∝ surface area X difference in concentration/length of diffusion path
