general gas exchange Flashcards
How do single-celled organisms exchange substances with their environment? (2)
Single celled organisms have a large SA:V
Allowing substances to enter easily and quickly by simple diffusion due to the short diffusion distance
Why do multicellular organisms need specialised exchange surfaces? (3)
They have a small surface area to volume ratio, making diffusion less efficient
Some cells are deep within the body, increasing diffusion distance
Multicellular organisms have a higher metabolic rate than single-celled organisms
How do you calculate the surface area to volume ratio? (2)
Divide the surface area
By the volume
Why are specialised transport systems needed in multicellular organisms? (2)
They ensure that dissolved gases and other substances
Can move to and from respiring tissues quickly and efficiently
How do small terrestrial animals like worms exchange gases? (4)
Worms use their moist outer body surface for gas exchange
They have an elongated body to increase SA:V ratio
They also have a primitive circulatory system
To maintain a concentration gradient for efficient gas exchange
How does a large surface area aid with exchange in root hair cells? (2)
Increases the rate of water absorption by osmosis and mineral ion uptake
By active transport from the soil
Why is a thin exchange surface in the alveoli important for diffusion? (3)
Made of a single layer of thin, flat cells called alveolar epithelium
This decreases the diffusion distance for oxygen (O₂) and carbon dioxide (CO₂)
Increasing the rate of diffusion
How do alveoli maintain a concentration gradient for efficient gas exchange? (4)
Alveoli are surrounded by a capillary network
Providing a constant blood supply to carry O₂ away and bring CO₂ to the alveoli.
The lungs are also ventilated, replacing air in each alveolus
To maintain a concentration gradient of O₂ and CO₂
What are the fish gills? (2)
The gas exchange surface in fish
Exchanging O₂ and CO₂ between the blood and surrounding water
How do fish gills facilitate efficient gas exchange? (3)
They have a network of capillaries for a good blood supply and are well ventilated as fresh water passes over them
These features maintain a concentration gradient for O₂
Increasing the rate at which O₂ diffuses into the blood
