Adaptations for Gas exchange Flashcards
What is surface area
The total area of an organism that is exposed to the external environment
What is the volume
The total internal volume of the organism
What happens as the size of an organism increases
Surface area to volume ratio decreases
Surface are and volume formula for a cube
Sa= length x length x 6
V=length^3
Surface area and volume formula cuboid
2 x (length x height + length x width + width x height)
Volume = length x height x width
Surface area and volume formula for cylinder
SA= circle + round bit
2pir^2 + 2pi x rh
Volume =
Pi x r^2 x h
What does the agar block practical measure
The effect of changing surface area to volume ratio on diffusion
By timing rate of diffusion through different sized cubes of agar
Method for agar cube practical
Coloured agar is made up and cut into cubes of 0.5 , 1, 2 (cm^3)
Calculate the surface area, volume and ratio between the two for each cube
Place cubes into boiling tubes containing a diffusion solution (HCl)
Same volume of HCL
Measure the time taken for the acid to completely change the colour of the indicator in the agar blocks.
why do small single celled organisms need a high sa :v ratio
allows for the exchange of substances by simple diffusion
LARGE SA: maximum absorbtion of nutrients and gases and secretion of waste products
SMALL VOLUME: small diffusion distance
how do large organisms get around having a small SA:V
large variety of specialised cells to facilitate the echange of substances between their environment
what two gases mean that a specialised system is used in large animals and why are they so important
oxygen - most organisms require ATP for biological procceses which is produced through aerobic respiration - requiring oxygen
Carbon Dioxide - waste product of aerobic respiration, alters PH of cells = bad. It must be removed by the specialised system
why is diffusion not viable for multicellular organisms
longer distance
oxygen takes too long to diffuse into the cells
organism dies
what is the metabolic rate of an organism
the amount of energy expended by that organism within a given period of time
what is the BMR
basal metabolic rate - the metabolic rate of an organism at rest
thus only energy required for functioning of vita;l organs
what is the relationship between metabolic rate and body mass
the greater the mass of an organism , the higher the rate
eg. a rhino will require more atp than a mouse
3 adaptations of gas exchange surface
Large surface area
Short diffusion distance
Concentration gradient
Why is there a need for gas exchange systems in larger organisms
Oxygen cannot only diffuse by simple diffusion as the distance would be too long so diffusion takes too long and the diffusion would be too inefficient and the organism would die
What do all insects have
Rigid exoskeleton with a waxy coating that is impermeable to gases
What is a spiracle
And what does it do relating to gases and water
An opening in the exoskeleton of an insect which has valves
Allowing air to enter the insect and flow into the system of trachea - most of the time the spiracle is closed to reduce water loss
What are trachae
Tubes which lead to the trachaeoles
They are reinforced to keep them open as the air pressure inside them fluctuates
How is a concentration gradient maintained between tracheoles and muscle cells
Oxygen is constantly being used up in respiration - allowing more oxygen to move into the cell by diffusion
This also produces co2 in respiration meaning that it moves out of the cells down the conc gradient
How do very active insects get a more rapid supply of oxygen
Create a mass flow of air by
Closing the spiracles, using muscles to create a pumping movement for ventilation.
The production of lactate from lactic acid in cells lowers the water potential of muscle cells
Water moves into the muscle
Allows gases to diffuse faster
What contains more oxygen , air or water?
Air contains around 30x more oxygen than water
How are fish adapted directly to extract oxygen from water
Series of gills on each side of the head
Each gill is attached to filament
Which is attached to lamellae
Lamellar consists of a single layer of flattened cells that cover a vast network of capillaries
Counter current mechanism for converting water to oxygen
Blood flow is in the opposite direction to the flow of water
This ensures the concentration gradient is maintained along the whole length of the capillary
The water with the lowest oxygen concentration is found adjacent to the most deoxygenated blood
Adaptations of a leaf to aid the uptake of carbon dioxide
Give the mechanism of this
When guard cells are turgid the stoma is open allowing air into the leaf
Air spaces within the spongy mesothelioma layer allows carbon dioxide to rapidly diffuse into cells
Carbon dioxide is used in photosynthesis - thus maintaining the concentration gradient
Short diffusion pathway with stoma
Structures in the leaf
Waterproof cuticle
Upper epidermis - tightly packed cells
Palisade mesophyll - elongated cells with chloroplasts
Spongy mesophyll - layer of cells that contains an extensive network of air spaces
Stomata - pores which allow air to enter
Guard cells - control opening or closing of stomach
Lower epidermis - tightly packed cells
What effect do adaptations that reduce water loss have on gas exchange
Negative affect on gas exchange
How do insects minimise water loss
Waterproof exoskeleton that prevents water loss
Ability to close spiracles
Hairs around spiracles - trap water - water potential outside insect on spiracle is high so water cannot leave cell from high to low wp
How do xerophytic plants minimise water loss
Few stomata
Hair surrounding stomata
Needle shaped leaves - reduced surface area
Thickened waxy cuticle
Adaptations of cacti
Spines that cannot photosynthesise
Thick cuticle
Large stem - stores water
Has both shallow and deep roots allowing it to access all available water
Adaptations of Mara grass
Leaves can roll up to limit exposure to wind
Exposed surface has no stomata and thick cuticle
Large number of hairs
