Lesson 3 - Gas exchange in insects Flashcards
(19 cards)
meaning spiracles
openings along the side of the thorax and abdomen of an insect that are the site of the entry and exit of the respiratory gases. They may be opened or closed by sphincters
meaning tracheae
A series of large tubes that transport air into the body of the insect. Tracheae are lined with chitin, which strengthen the walls and prevent them from collapsing
meaning tracheoles
very small tubes that spread between individual cells and delivers oxygen throughout the body.
describe the issues facing gas exchange in insects
- very active
- their exoskeleton which doesn’t allow gases to pass through
- terrestrial, so more difficult to exchange gases in atmosphere than in the water
- insects don’t have blood pigments to transport oxygen
what happens to the sphincters when an insect becomes active
there is a higher oxygen demand, so more spiracles open
what happens inside the trachea when an insect becomes active
When the insect becomes active, lactic acid builds up in the muscle tissue. This lowers the water potential of the cells, causing tracheal fluid to leave the tracheoles by osmosis This increases the surface area of the tracheole wall, increasing the rate of diffusion of oxygen from the tracheole into the fluid.
what is the effect of the tracheoles containing tracheal fluid towards the ends of their lengths
This limits the penetration of the gases by diffusion
what is the function of the opening and closing of the spiracles
- to limit water loss
- to control the rate of gas exchange in an insect
how does the opening and closing of the spiracles control the rate of gas exchange in an insect
it’s coordinated by respiratory centres in the nervous system, which are stimulated by increasing carbon dioxide levels and by lactic acid that builds up in active tissue where there is a lack of oxygen
explain how mechanical ventilation helps very active insects with respiration
when air is actively pumped into the tracheal system, the spiracles open and the insect makes muscular pumping movements of the thorax, abdomen, or both. These ventilation movements change the volume and therefore the pressure inside the body, drawing air in and out of the tracheae and tracheoles
how do collapsible tracheae or air sacs help very active insects with respiration
the collapsible tracheae and air sacs act as air reservoirs. They increase the volume of air moved through the respiratory system. The ventilating movements of the thorax and abdomen inflate and deflate them.
why is it difficult to drown an insect
the insects close their spiracles by the sphincters, so that water doesn’t enter their respiratory system
what happens to the tracheae when large insects fly
the tracheae expands into air sacs
what are the adaptations of the trachioles
- very thin walls
- large surface area
- no chitin, so gases can cross them
- moist
- ends of tracheoles are in direct contact with individual cells
explain how gas is exchanged in insects
gases enter though the open spiracles, down the concentration gradient by simple diffusion. Air is drawn into the insects as oxygen is moved into the cells from the ends of the tracheoles, creating a concentration gradient. Carbon dioxide leaves through the same methods.
when do spiracles open
when there’s a low concentration of oxygen inside the tracheae, causing the spiracles to open to allow oxygen to enter and carbon dioxide to leave
when do spiracles fully open
spiracles only fully open for a short period of time, to maximise oxygen intake and carbon dioxide output, but minimise water loss
how are spiracles opened
respiratory centres in the nervous system are stimulated by the increase in lactic acid in the respiring muscles and the lack of oxygen which help to regulate the opening and closing of the spiracles
describe 5 ways by which gas exchange is adapted
- opening and closing of the spiracles
- ventilation of the tracheae by muscular contractions of the abdomen, which create pressure changes and draw air in
- internal air sacs act as reservoirs
- fluttering of the spiracles to waft oxygen in whilst reducing water loss
- holding on to carbon dioxide until it builds up to a high level in the body fluids, and then opening the spiracles and releasing it all at once
