⭐️Exchange: Exchange Between Organisms And Their Environment Flashcards
What is tissue fluid?
The environment around the cells of multicellular organisms
Give 4 examples that need to be interchanged between an organism and its environment
Respiratory gases, nutrients, excretory products and heat
Except from heat, how can the exchanges between the body and its environment take place?
- Passively (diffusion and osmosis )
- actively (active transport)
What features have organisms that rely on diffusion to exchange substances with the environment evolved? Give examples for each
- a flattened shape so that no cell is far from the surface e.g. flatworms or leaves
- specialised exchange surfaces with large areas to increase the SA:V e.g. lungs in mammals or gills in fish
What’s the formula for the surface area of a sphere?
4 πr^2
What’s the formula for the volume of a sphere?
4/3 πr^2
Give 5 features of specialised exchange surfaces
- they have a large surface area to volume ratio of the organism to increase the rate of exchange
- they are very thin so diffusion distance is short allowing materials to cross the exchange surface rapidly
- they are selectively permeable to allow selected materials to cross
- they have a moving environmental medium (e.g. air) to maintain a concentration gradient
- they have a transport system to ensure the movement of the internal medium (e.g. blood) to maintain a diffusion gradient
What does ficks law state?
Diffusion is directly proportional to:
(Surface area x difference in concentration)/length of diffusion path
What is the gas exchange system of insects composed of and describe each one
- tracheae, an internal network of tubes held open by rings of chitin to prevent them collapsing
- traheoles, divisions of the tracheae which are dead end tubes which extend throughout the body tissue of the insect and so carry air with oxygen towards respiring tissue. There’s a short diffusion pathway between the tracheae and the cells
- spiracles, tiny pores on the side of the body surface through which gases enter and leave and can be closed and opened by valves
How do gases move in and out of the tracheal system along a diffusion gradient?
- When cells are respiring, oxygen is used up so it’s concentration towards the ends of the tracheoles falls
- This creates a diffusion gradient that causes oxygen to diffuse from the atmosphere, along the tracheae and tracheoles into cells
- CO2 is produced by cells during respiration creating a diffusion gradient in the opposite direction
- This causes gaseous co2 to diffuse along the tracheoles and tracheae from the cells and to the atmosphere allowing respiratory gases to be exchanged quickly because diffusion in air is more rapid than in water
How are respiratory gases moved in and out of the tracheal system by mass transport?
As the contraction of muscles in insects squeeze the trachea allowing mass movement of air in and out, further speeding up the exchange of respiratory gases
How are respiratory gases moved in and out of the tracheal system by the ends of the tracheoles being filled with water?
- During periods of major activity like flying, muscle cells around the tracheoles carry out anaerobic respiration
- This produces lactate which lowers the water potential of the muscle cells causing water to move into the cells from the tracheoles by osmosis
- The water in the ends of the tracheoles decreases in volume and on doing so draws air further into them
- This means the final diffusion pathway is in a gas rather than in a liquid phase hence diffusion is more rapid increasing the rate at which air is moved into the tracheoles however this leads to greater water evaporation
Give a limitation of the tracheal system in insects
It relies mostly on diffusion to exchange gases between the environment and the cells and to be effective, the diffusion pathways needs to be short hence why insects are small. This means the diffusion pathway limits the size insects can attain
Give an overview of the process of water movement in the gills of a fish
- Water is taken in through the mouth and forced over the gills and out through an opening behind the gills
- Oxygen dissolved in the water is absorbed by the gills
- The movements of the mouth, floor and operculum are coordinated to produce a stream of water that goes in through the mouth, over the gills and out through the operculum
- The water is kept moving over the gills by a ventilation system
Give the structures of the gills and what they each do
- gill arc: supports the gills and the associated blood vessels
- gill filaments: increase the surface area of the gills
- gill lamellae: positioned at right angles to the gill filaments, further increase surface area and are the site of gas exchange