Gas Exchange in fish, insects, plants Flashcards
What substances do you need to exchange with the environment?
- oxygen
- waste (CO2, urea)
- heat (so temperature remains constant)
- water (for water regulation)
How are large organisms adapted for gas exchange?
- They don’t have enough surface area in order to diffuse through their surface as not enough oxygen will be supplied in time.
- They increase surface area by:
* having additional absorbing areas
* adapting their shape
* having transport systems to keep the distance of diffusion to a minimum
How are small organisms adapted for gas exchange?
they have a high surface area to volume ratio so they get their oxygen through their bodies’ surface via simple diffusion
What determines the amount of oxygen an organism needs?
- amount of living cells
- rate they need to respire
What makes a good exchange surface?
- thin so their is a short diffusion pathway
- large surface area to volume ratio
- partially permeable so particles can pass without obstructions
- has an environment of internal and environmental medium
- moist as substances dissolve in solutions mechanisms to maintain diffusion gradient
What problems do land animals face?
The cells need to be exposed to air in order for oxygen to diffuse into the organisms. However they’re also made of a high percentage of water so when they are exposed to air, the water molecules evaporate, causing the cells to dehydrate.
What problems do flatworms (and tubular or thin organisms) face?
They are flat (tubular/thin) so they lack specialized exchange systems
How do flatworms face their problems?
They use their outer surface for gas exchange by diffusion as their cells are localized near the equator so gas can exchanged cell by cell
How do earthworms face large organism problems?
- their thin walled blood vessels (capillaries located around the body) act as specialized exchange surfaces
- they also respire through their surface
- they live in damp environments and are covered in slime in order to reduce water loss from being exposed to air
What problems do insects face?
They are usually terrestrial so water evaporates easily from their body, which causes them to become dehydrated
How do insects face these problems?
- They reduce water loss by:
. they have rigid coverings with waterproof cuticles
. they have a small surface area to volume ratio - They have a tracheoles that supplies air to every tissue
How to measure the surface area of a leaf?
- draw around the leaf of a graph
- count the squares
- then multiply by 2
How do scientists ensure they make a valid comparison between leaves from different species?
They use fully grown leaves
What is the relationship between size and surface area to volume ratio of organisms?
As size increases ratio of surface area to volume decreases
What is the relationship between metabolic rate and surface area to volume ratio of organisms?
As size increases ratio of surface area to volume decreases
why oxygen uptake is a measure of metabolic rate in organisms?
Oxygen is used in respiration which is a metabolic process
How do plants exchange gases?
Their gas exchange surface is the surface of mesophyll cells that are in contact with the air
What problems do plants face?
Losing water through gas exchange (evaporation) from the wet cell walls and lost through transpiration
What adaptations do plants have?
- the mesophyll cells (their gas exchange surface) is surrounded by air spaces which creates a large surface area for diffusion
- the stomata opens and closes to control the amount of water loss
How does the stomata open and close?
It’s surrounded by guard cells that open and close:
They open by absorbing water (through osmosis), causing it to become turgid and the inner walls to resist expansion and become curved
They close by losing water (through osmosis), causing it to become flaccid and collapses
What does the stomata respond to?
- high humidity
- low temperature
- wind
What do plants do when it’s dark?
They don’t photosynthesize, thy just diffuse
How do plants limit their water loss while still allowing gas exchange?
The stomata (regulated by guard cells) close to prevent water loss but opens to let oxygen in
How are (Xerophyte) plants adapted to minimize water loss?
They have:
1. thick waxy cuticles
2. sunken stoma
3. hairs on their leaves
4. folded/curved leaves
5. small leaves/spines
6. stoma on their lower leaf
7. sheading leaves in cold/dry climates
8. stomatal hairs
9. succulent leaves/stems
10. extensive roots
What are examples of plants with thick waxy cuticle?
most dicots
What are examples of plants with small levs/spines?
- plants with conifer needles
- cacti with spines
What issues do fish have when exchanging gases?
they have an impermiable membrane so gases can’t diffuse through skin
How are fishes adapted for gas exchange?
they has specialised structures (gills) that perform gas exchange instead of their surface
Describe the structure of a gill.
- in bony fish there are 4 gills
- gills are supported by an arch
- lamellae are on the gills
- gills are made up of gill filaments
lamellae participate in gas exchange
Describe counter-current direction.
- blood and water flow across the lamellae in opposite diractions
- ensures that a steep diffusion gradient is maintained
- this means that a max amount of oxygen diffuses into deoxygenated blood
Why can’t fish survive long out of water?
- the water flow separates the gill filaments
- this prevents them from sticking together which reduces their SA:V which reduces the amount of oxygen that can diffuse into the blood
Describe the process of ventillation in fish?
- fish lowers the floor of buccal cavity (opens mouth), allowing water to flow in
- floor of buccal cavity rises (mouth closes) which increases the pressure
- pressure change between the mouth cavity and opercular cavity, forces water of gill fillaments
- operculum acts as a valve and pump and lets water out and pumps it in
Why does ventillation in fishes occur?
to maintain a continuous unidirectional flow
