3.3.1 Exchange Flashcards
Describe the structure of an insects gas exchange system
Insects have small openings in their exoskeletons called spiracles, small tubes called tracheae divide into even smaller tubes called tracheoles. The ends of the tracheoles are filled with liquid when the insect is at rest.
Describe the relationship between size of organism and surface area to volume ratio
The larger the organism, the smaller the surface area to volume ratio
Explain why larger organisms need specialised gas exchange systems
Because they have a smaller surface area to volume ratio so can’t absorb all the gases they need by simple diffusion so they need a specialised system to provide short diffusion pathways, large surface area and maintained concentration gradients
Describe the structure of fish gills
Fish have many gill filaments, each covered in many lamellae providing a large surface area for gas exchange. The blood in the capillaries flows in the opposite direction to the water.
Explain why a counter-current flow more efficient than co-current flow in fish gills
Because the blood continues to pass water which has a higher oxygen concentration, so the concentration gradient is maintained along the whole length of the gill filament
How do insects limit water loss from their bodies?
They are covered in a water proof exoskeleton and can control the opening and closing of spiracles
Describe the process of gas exchange in leaves
Air diffuses into the stomata and into the spongy mesophylly layer where it surrounds the cells, CO2 diffuses into cells and oxygen diffuses out creating a concentration gradient between the inside and outside of the leaf, this causes CO2 to continue to diffuse into the leaf and O2 to diffuse out.
Explain why having hairs under leaves, rolled leaves helps a xerophytic plant to survive
This traps a layer of humid air near the stomata so there is a low water potential gradient between the air inside and outside of the leaf. This means that less water is lost by the plant.
List 4 adaptations of xerophytic plants
Less stomata, smaller leaves, rollled leaves, hairs under leaves, stomata in pits or grooves
What is tidal volume?
The volume of air in breathed in and out at each breath at rest
How do you calculate Pulmonary ventilation?
PV = Tidal volume x breathing rate
What is breathing rate?
Number of breaths are taken per minute
Describe inhalation
Diaphragm contracts, external intercostal muscles contract, chest volume increases, pressure in chest decreases, atmospheric pressure forces air into lungs, lungs expand to equalise pressure
Describe exhalation
Diaphragm relaxes, external intercostal muscles relax, chest volume decreases, pressure in chest decreases, air is forced out of lungs until air pressure inside and outside chest is equal
State two substances produced by the stomach
Hydrochloric Acid, protease enzymes, mucus lining