Surface area to volume ratio Flashcards
What is metabolic rate ?
All the chemical reactions in the body including respiration
Organisms need to exchange substances with their environment:
Cells need oxygen and nutrients
Organisms need to excrete waste products
Heat needs to be exchanged as most organism need to stay at the same temperature
How do organisms exchange their substances ?
Surface area to volume ratio
Their habitat
What is the total oxygen requirement correlated to ?
Total volume
What is the rate of absorption of gases by an organism correlated to ?
The size of its surface area
Larger membrane would mean more molecular movement
How do single celled organism exchange gases across their body surface ?
By diffusion with their environment
Short diffusion pathway as they are small
Larger organisms have a low surface area to volume ratio, what does this mean ?
Diffusion is too slow as some cells are deep within the body
A large volume of animal has requirements too high for the available surface area
How do the large organisms overcome this ?
Some organisms have evolved to have a body shape which maximises their surface area by being flattened or elongated
Some organisms have developed specialised exchange organs and delivery systems to maximise gas exchange and transport
For example gills in fish and lungs in mammals
Gills are folded into lamella
Lungs are folded into alveoli
What have insects developed ?
A tracheal system which is a series of specialised tubes in direct contact with cells. They also maintain a short diffusion distance
How do smaller animals maintain a constant temp ?
Smaller animals a have a larger surface area to volume ratio so they radiate more heat to maintain this they have a higher metabolic rate which means they do more chemical reactions such as respiration which releases heat
What are the adaptations for heat loss ?
To increase surface area: larger ears longer faces longer noses
To reduce surface area: larger body size smaller ears compact facial features
