Gas Exchange Flashcards
(54 cards)
Fish : explain how the gills allow efficient gas exchange
Thin lamellae provide a large surface area
Thin epithelium so short diffusion pathway
Counter current flow maintains the concentration gradient across whole length of gill
Lots of blood capillaries and thin surface of cells to speed up diffusion between water and blood
Fish: explain how the highly folded structures of the gill lamellae increase the efficiency of gas exchange
They increase the surface area over which diffusion can take place
Fish: describe and explain how the counter current system leads to efficient gas exchange across the gills of a fish
Water and blood flow in opposite directions
This maintains a concentration gradient across the whole length of the gill
As much oxygen as possible passes into the blood
Name the process by which carbon dioxide is removed from a single called organism
Diffuses out across their body surface
How do single celled organism absorb oxygen
Diffusion across their body surface
What do single celled organisms have that’s different to multicellular organisms
Large SA to volume ratio
Insects: explain how the tracheal system limits the size of the insect
The tracheal system relies on diffusion to bring oxygen to respiring tissues if insects were large it would take too long for oxygen to reach the tissues rapidly enough to supply the insects needs
Insects : give 2 explanations as to why the rate of water loss during gas exchange is very low in most insects
Insects have spiracles that can close to reduce water loss
Insects have sunken spiracles that trap moist air
Explain ways in which plants limits water loss
Plants have a waxy cuticle which prevents the evaporation of water
Plants have hairs on their surface (lower epidermis) that trap moist air reducing water potential gradient. So less water lost by evaporation
Plants have sunken stomata which again traps moist reducing water potential gradient
The stomata can close which reduces evaporation
Leaves: why is there is less water lost by a plant when the air is humid
Humidity reduces the difference in concentration of water between the plant and air. Reduced concentration gradient= less water loss
What are xerophytes ?
Plants that are adapted to living in areas where water is in short supply
Give two examples of how xerophytes limit water loss
Thick cuticle - Waxy cuticle Rolled up leaves Hairy leaves Stomata in pits or grooves Reduced surface area to volume ratio Deep roots sunken stomata
Xerophytes: explain how having rolled up leaves reduces water loss
Traps a region of still air within the rolled leaf
The trapped region has a high water potential
No water potential gradient between the inside and outside of leaf and therefore no water loss
Xerophytes: explain how having hairy leaves reduces water loss
Traps still moist air next to the leaf surface
This reduces the water potential gradient between the inside and the outside of the leaves
Less water lost by evaporation
Xerophytes : explain how having stomata in pits or grooves reduces water loss
Trap moist air next to the leaf and reduce the water potential gradient
Why water is always lost from the gas exchange of terrestrial organisms ( insects and plants)
Gas exchange surfaces are permeable
Higher concentration of water molecules inside the animal than outside
Water will diffuse out
Leaves: what happens to oxygen in a plant
Some oxygen from photosynthesis is used in respiration
Most diffuses out of the plant
Plants: in the dark when photosynthesis is not occurring what is happening to oxygen and carbon dioxide
Oxygen diffuses into the leaf because constantly being used by cells during respiration
Carbon dioxide diffuses out of leaf because it is constantly being produced
How is gas exchange similar in insects and plants
No living cell is far from the external air and therefore is a source of oxygen and carbon dioxide
Diffusion takes place in the gas phase (air)
Both have small surface area to volume ratio
How are leaves adapted for rapid diffusion
Air spaces have a very large surface area to volume ratio
Many small pores called stomata so no cell is far from stoma so short diffusion pathway
Numerous interconnecting air spaces that occur throughout the mesophyll so that gases can readily come in contact with mesophyll cells
Large surface area of mesophyll cells for rapid diffusion
At times what can plants do with the gases they produce
The gases produced in one process can be used for the other
Photosynthesis + carbon dioxide
What is each stoma surrounded by
A pair of guard cells
What do guard cells do ?
Open and close the stomata (for example when it is dark)
Why is the stomata being able to open and close important ?
The stomata can close when there will be excessive water loss to minimise water loss
