Gas exchange structures in organisms Flashcards
What is gas exchange
the process by which an organism interchanges gases such as oxygen and carbon dioxide with its environment
What are the four requirements of gas exchange surfaces
Large surface area: more physical space for gases to diffuse across
Protected from desiccation (drying out): gases are exchanged in solution (desiccation = no solution = no exchange)
Constant contact with air or dissolved gases: abundance of external gas creates a concentration gradient between environment and gas exchange surface enabling transport by diffusion
Able to transfer gases into the body’s cell: transport gases to tissues that require it (part of organisms metabolism/cellular respiration)
Describe the respiratory system of amphibians
they have a single smaller lung. However they also have capillaries close to the skin enabling diffusion across the skin. This means they have a large surface area but are at risk of desiccation and hence need to live in moist environments.
Describe the respiratory system of fish
as gases have low solubility in water they need to have very efficient methods of gas exchange. They possess gills in which water flows exchanges gases. Blood and water flow counter-currently to maintain a concentration gradient and ensure maximum oxygen uptake.
Describe the respiratory system of insects
Possess an exoskeleton to prevent desiccation –> but also easy gas exchange.
Possess small openings “spiracles” controlled by valves which enable gas to travel directly into its cells, bypassing the need for a circulatory system
Describe the respiratory system of plants
Flat=large SA;V
stomata (pores) which guard cells open and close by swelling and shrinking –> allows gas to flow into and out of the gaps in mesophyll.
If stomata are open too long they lose too much water –> need for regulation
What are triggers that cause stomates to close
low levels of water (water stress)
high sun exposure
winds
low humidity
as such open for most of the night and during the day (high light intensity means a greater opportunity for photosynthesis which is more important than water conservation)
