Adaptations for gas exchange Flashcards
What is a respiratory surface?
It is the surface at which diffusion of gases in and out takes place.
Name some examples of respiratory surfaces?
Gills of a fish, alveoli in mammalian lungs, tracheae of an insect and the spongy mesophyll cells in leaves
What are the essential features of exchange sources for rapid diffusion of gases?
A large surface area relative to volume so the right satisfies the organisms needs.
Thin - so has a short diffusion pathway.
Permeable - so the rate of diffusion as quick as the respiratory gases confuse easily.
Have a moist environment - so gas exchange can occur.
A mechanism which provides a steep concentration gradient across the surface by bringing oxygen in and removing carbon dioxide rapidly.
What are unicellular organisms?
Single celled organisms.
Gas exchange of a single cell organism
Single cells have a large surface area to volume ratio. A thin cell membrane means that the diffusion pathway is short so diffusion can occur rapidly. The single cell can therefore absorb enough oxygen across the cell membrane fast enough to make its oxygen demands and needs respiration as well as removes CO2 quick enough to prevent the high concentration buildup which would cause the conditions in the cytoplasm to be too acidic for the enzyme to function
Gas exchange of multicellular organisms?
In larger organisms many cells are aggregated together. They have a lower surface area to volume ratio compare to small organisms so diffusion alone these surfaces are less efficient for their gas exchange
Describe the gas exchange of a flat worm?
They are aquatic organisms which gases diffused into. They have a smaller surface area to volume ratio. They are flattened which reduces the diffusion distance, so gas exchange can occur quickly and efficiently. It has a permeable surface so gases can reach the cells. It doesn’t contain a circulatory system, so relies on the external surface for gas exchange as it’s the only way oxygen can reach respiring cells.
Describe the gas exchange of a earthworm?
These are terrestrial organisms. It has a cylindrical shape so has a lower surface area to volume ratio compared to flat worms. The respiratory surface is their skin which is kept moist by mucus secretion. The need for a moist surface which restricts them to a damp environment of the soil. It has a low metabolic rate as it’s slow moving so has a low oxygen requirement. Enough oxygen can diffuse across its skin to blood capillaries. Earthworms have a circulatory system to deliver oxygen to the tissues by blood vessels which maintains a diffusion gradient at the surface. CO2 is also carried in the blood and it diffuses across and out of the skin down a concentration gradient.
What are the special features seen with multicellular organisms?
They generally have a high metabolic rate as they are active so have a ventilating mechanism to maintain gradient across respiratory surfaces. As they need to deliver more oxygen to respiring cells and removes more carbon dioxide.
An increase in size and specialisation of cells, tissues and organs become more interdependent.
They must actively maintain a steep concentration gradient across the respiratory services by moving the environment to medium; air and water and in large organism the internal medium, the blood so require ventilation mechanism.
Surfaces must be thin so the diffusion pathway is short but there is a risk of it being damaged as they are fragile. But as their inside organism they are protected. Many respiratory services are adapted to environmental conditions.
How would you describe the relationship of oxygen required to the total volume?
The total option requirement of an organism is proportional to its total volume. The rate of absorption is proportional to the organisms surface area.
What happened to the surface area to volume ratio when the size increases?
The ratio decreases
What are the major problem is terrestrial organisms face?
Evaporation of water from the body surface which could lead to dehydration. Gas exchange surfaces need to be thin, permeable with a large surface area. As water molecules are very small they can pass through the surfaces as they are moist are likely to lose a lot of water.
How have internal lungs minimised problems?
They have minimise heat and water loss and allow gas exchange with air and allow animals to be very active.
Explain gas exchange of amphibians?
Their skin is moist and permeable with a well-developed capillary network below the surface. Gas exchange occurs to the skin and the lungs (when active). It provides a large surface area to volume ratio. Additionally the shorter diffusion pathway allows gas exchange to occur efficiently. They provide a good blood supply of the heart and cardiovascular system
Explain gas exchange of reptiles?
Reptiles lungs have a complex structure compared to an amphibians increasing the surface area for gas exchange. The lungs and moist and permeable with a shorter fusion pathway as the walls are thin with a good blood supply. The alveoli aligned with single squamous epithelial cells providing a short pathway. They are adapted to minimise heat and water loss.
Explain gas exchange of birds?
A bird processes a large volume of oxygen as flight requires a lot of energy. Birds do not have a diaphragm but the ribs and flight muscles ventilate the lungs more efficiently than other methods used by vertebrates.
What do many terrestrial organisms have to reduce water loss?
A waterproof layer covering the body surface in order to reduce water loss e.g. the exoskeleton of an insect is rigid and comprises a thin waxy layer over a thicker layer of chitin and protein.
Why can’t an insect use its body surface for gas exchange?
As it has a small surface area to volume ratio they won’t be able to use their bodies surface to exchange enough gas by diffusion therefore gas exchange occurs repaired holes called spiracles which runs along the side of the body.
Describe how gas is exchanged in an insect?
It occurs through paired holes called spiracles which run along the side of the body. The spiracles lead into a system of branched ringed air tubes called tracheae which branch into smaller branches called tracheoles. Chitin is found in the trachea which is strong and holds the tubes open as it is impermeable so no gases can diffuse out (which also reduces water loss by evaporation). The spiracles can open and close controlling gas exchange and water loss. With the hairs found at the end of spiracles contributing to the prevention of water loss as well as preventing solid particles getting it.
How many pairs of spiracles are there?
2 thoracic and 8 abdominal
What does the tracheal system provide?
A large surface area for gas exchange making it efficient. However diffusion is only efficient over short distances limiting the size of the insect. Small insects can rely on diffusion only when taking oxygen and removing carbon dioxide however large insects need to adapt so they have to ventilate their tracheal system by rhythmical body movements which suck air in and pump it out.
What happens during periods of rest and activity for insects?
When at rest they rely on diffusion through the spiracles, tracheae and tracheoles when taking oxygen in and removing carbon dioxide. During periods of activities the abdomen ventilate the tracheae.
How does ventilation occur in insects?
Air flows in through the thoracic and the first two abdomen spiracles and air flows out of the remaining abdominal spiracles. Air is moved by the contraction and relaxation of the muscles in the abdomen. This causes the abdomen to change in size and cause pressure changes
What happens during inspiration of an insect?
The 2 thoracic spiracles and 2 abdominal spiracles open, with the 6 other abdominal spiracles closed. The abdomen expands causing a decrease in pressure so air flows in.
What happens during expiration of an insect?
The 2 thoracic and 2 abdominal spiracles close, with the 6 other abdominal spiracles open. The abdomen contracts causing a increase in pressure as air flows out.
What is a feature of the air sacs in the insect?
That they are compressible so makes the amount of air exchanged larger.
What is found at the end of the tracheoles?
Fluid
Why is the fluid at the end of the tracheoles?
As they are close to muscle fibres when there is low oxygen in the muscle cells it produces lactic acid causing a decrease in water potential. The fluid will start to move out of the tracheoles into the muscles by osmosis meaning the gases are interacting with muscle cells making diffusion of oxygen more efficient. No respiratory pigment is required. Carbon dioxide diffuses out by the reverse process. At rest fluid is released back into the tracheole so carbon dioxide can be removed.
What do the spiracles have?
Valves which are open and close to reduce water loss.
