3 Exchange (gases and digestion) Flashcards
How do smaller organisms allow efficient exchange?
Smaller organisms have a surface area that is large enough, compared to their volume.
Larger organisms have have volumes that are bigger than their surface area. why is this a problem?
Simple diffusion of substances would not be able to supply enough and it would take too long for the substance to move to the middle of the organism.
how have organisms evolved to overcome the high volume:low surface area problem?
- A flattened shape to increase surface area e..g leaf
- Specialised exchange surfaces with large areas e.g. alveoli in lungs or gills in fish
Why do special exchange surfaces have to be thin and selectively permeable?
To ensure diffusion is short and selected materials are allowed to pass. This fastens up the process.
What else is important to maintain in exchange surfaces and why?
Maintaining a diffusion gradient is important to ensure the movement of the internal medium (eg blood) and the environmental medium (eg air)
what is diffusion directly proportional to?
diffusion ∝ (surface area x difference in concentration) / length of diffusion path
What happens at the body surface of single-celled organisms?
Gas exchange takes place at the body surface of single-celled organisms. Oxygen gets absorbed in by diffusion and Carbon Dioxide diffuses out.
What are the internal network of tubes called in an insect?
They are called trachea. They are supported by rings to prevent them from collapsing.
What is the job of tracheoles?
Tracheoles extend into the body of the insect, which are branched off trachea. They provide the respiring tissue in the body with Oxygen as there is short diffusion from the tracheole to the body cell.
