the need for specialised exchange surfaces Flashcards
what do living things need to survive
need a supply of oxygen and nutrients to survive.
why do living things need to remove waste products
so they dont build up and become toxic
why dont small organisms need a specialised exchange system
all of its oxygen needs and the waste carbon dioxide can be exchanged with the external environment by diffusion through the cell surface
what can diffusion provide the needs for
single celled organisms
why can diffusion easily provide the needs for single celled organisms
- the metabolic activity is usually low so the oxygen demands and carbon dioxide production is low
- they have a large surface area to volume ratio
- the cytoplasm is close to its environment so diffusion can supply its needs efficiently
why is surface area to volume ratio
surface area of an organism divided by its volume expressed as ratio
what happens as organisms get larger
they are made up of many more cells arranged in tissues, organs, organ systems
what is different about larger organisms compared to single celled organisms
- they have a higher metabolic activity
- smaller surface area to volume ratio
- gases can’t be exchanged fast enough or in large amounts for the organism to survive
why do multicellular organisms have a larger diffusion pathway
layers of cells increase so most of the cells aren’t in direct contact with the external environment. they need specialised cells to carry out particular functions
where does metabolic activity get its energy
food
what does metabolic energy require energy in
aerobic respiration
why do cells need good supplies of nutrients and oxygen
to supply the energy in movement. it increases in animals that use energy to keep themselves warm
why do small organisms have a large surface area to volume ratio
they have a large surface area compared to their volume (small volume)
they can supply cells with sufficient oxygen
why do larger organisms have a small surface area to volume ratio
they have a small surface area compared to their large volume
why is it difficult for substances to travel multicellular organisms
they need to travel to reach the cells to supply its needs. makes it harder to absorb enough oxygen
