Adaptations for gas exchange Flashcards
(28 cards)
What causes air to enter the lungs?
Pressure inside the lungs must be below atmospheric pressure.
What is an insects exoskeleton made of? And why is a lipid layer important?
Made of a hard fibrous material for protection (chitin).
Lipid layer= Prevent water loss
What is the gas exchange system called in insects?
Tracheal system
What are the insect adaptations to prevent water loss?
-Small surface area to volume ratio where water can evaporate from
-Waterproof exoskeleton
-Spiracles, which can open and close to reduce water loss
-Hairs covering spiracles to prevent solid particles from getting in
What parts of the insect is involved in the tracheal system?
Trachea, tracheoles, spiracles
What are 4 key features of an efficient respiratory surface (alveoli, gills, etc)?
- Large surface area, relative to the volume of the organism
- Be thin, creating a short diffusion pathway
- Permeable, so that the respiratory gases diffuse easily
- Mechanism which produces a steep diffusion gradient across the respiratory surface, so gases are exchange rapidly.
What are some features of a unicellular organism e.g Amoeba? And why might this be beneficial?
- Single celled so it has a large surface area to volume ratio
- The cell membrane is thin so diffusion into the cell is rapid
- A single cell is thin so diffusion distances inside the cell are short
Therefore it can: absorb enough oxygen across the whole cell to meet their needs for respiration. Remove carbon dioxide quickly enough so that there isn’t a large buildup which would make the cytoplasm acidic (denature enzymes)
How have flatworms overcome the issue that multicellular animals have a lower surface area to volume ratio?
With flatworms being flat have a much larger surface area to volume ratio than spherical animals, this also means that the body is close to the surface at all times allowing for a short diffusion pathway.
Name 5 features of a earthworm:
- It’s cylindrical so the surface area to volume ratio is lower to that of a flatworm.
- It’s skin is the respiratory surface. It is kept moist by secreting mucus, which restricts the earthworm to the damp environment of the soil.
- Low oxygen requirement, as its slow moving and has a slow metabolism.
- Haemoglobin is present (carrying oxygen around the body in blood vessels), Carrying the oxygen away from the surface maintains a diffusion gradient.
- Carbon dioxide is also present in the blood and it diffuses across the skin, down a concentration gradient.
What are some features found in multicellular organisms and not in unicellular?
- Generally have a higher metabolic rate
- With increase in size, cells/tissues/organs became more interdependent
- Must actively maintain a steep concentration gradient across their respiratory surface by moving either the environmental or internal medium, therefore needing a ventilation mechanism
- respiratory surfaces must be thin to create a short diffusion pathway, but they need to be protected internally as they are fragile
What are some potential major problems for terrestrial organisms?
-Water molecules are small and can therefore easily pass through respiratory surfaces, so the surfaces are moist. But this means it’s likely to lose water
-Water evaporates from body surfaces which could result in dehydration
Why are cartilaginous fish less efficient for gas exchange than bony fish?
- They don’t have a special mechanism to force water over their gills, so they must constantly be swimming for ventilation to happen
- They have a parallel flow system- but it limits the oxygen intake to 50%
- Gas exchange in parallel flow does not occur continuously across the whole gill lamella
Describe the ventilation mechanism to take in water found in bony fish:
A) The mouth opens
B) The operculum closes
C) The floor of the mouth is lowered
D) The volume inside the mouth cavity increases
E) The pressure inside the mouth cavity decreases
F) Water flows in, as the external pressure is higher than the pressure inside the mouth
Describe the ventilation system to force water out and over the gills in bony fish:
A) Mouth closes
B) Operculum opens
C) Floor of the mouth raises
D) Volume inside the mouth cavity decreases
E) Therefore pressure will increase
F) Water flows over the gills and out because the pressure inside the mouth cavity is greater than the outside
Why do fish die if they are out of water?
Gill filaments are held apart by flowing water (the lamella is the respiratory surface and have a large surface area), without water the gill filaments stick together and collapse, making the surface area smaller and therefore not enough gas exchange is taking place.
What is the definition of counter-current flow?
Blood and water flows in opposite directions, maintaining the concentration gradient and therefore oxygen diffusion along the lamella entire length (allowing up to 80% uptake).
Explain why counter-current flow is a more efficient system:
At every point of the lamella the oxygen concentration in the water is higher than that of the blood, allowing oxygen to diffuse across the whole length (removes around 80% oxygen, cartilaginous fish- 50%).
Describe the placement of the pleural membrane, and what their function is:
-Pleural membrane surrounds each lung and lining of the thorax, between the membranes there’s a few cm of pleural fluid.
-The fluid is a lubricant, prevent friction between the lungs and inner wall of thorax when they move
Describe the process of inspiration:
A) The intercostal muscles contract
B) Ribs are pulled upwards and outwards
C) At the same time, the diaphragm muscles contract so it flattens
D) Outer pleural membrane is pulled up and out with the ribs, and the lower part is pulled down with the diaphragm. Inner membrane follows and so the lungs expand, increasing the volume inside the alveoli.
E) As there is more volume inside the thorax, the pressure inside the lungs is reduced
F) Atmospheric air pressure is now greater than inside the lungs, so air is forced in
Describe the process of Expiration:
A) Intercostal muscles relax
B) Ribs move down and inwards
C) Diaphragm muscles relax and domes upwards
D) Pleural membrane moves inwards with the ribs, decreasing the volume of the lungs and alveoli
E) Increases pressure inside the lungs
F) Air pressure in the lungs is not greater than atmospheric pressure- forcing the air out
Why is surfactant important and where is it found?
- It is an anti-sticking mixture, has a low surface tension which prevents the alveoli from collapsing during exhalation. It also allows gasses to dissolve before they diffuse in and out
- Alveoli
What are 5 things that make gas exchange in the alveoli efficient?
- Provide a large surface area to volume ratio
- Gases dissolve in the surfactant moisture lining
- Alveoli walls made of squamous epithelium which is one cell thick- diffusion pathways are short
- Extensive capillary networks which maintain a diffusion gradient
- Capillary walls are only one cell thick, contributing to the short diffusion pathway
Where does gas exchange happen in insects? Explain:
-The interface between tracheoles and muscle fibres
-Oxygen dissolves into the fluid and diffuses directly into the muscle fibres- no blood circulation is needed.
