Component 3.1 - Size And Gas Exchange Flashcards
What are the essential features of an efficient gas exchange surface?
Large SA - rate of gas exchange satisfies organisms needs
Be thin - short diffusion pathway
Be permeable - respiratory gases can diffuse easily
Have a mechanism to maintain a steep concentration gradient - by removing carbon dioxide or bringing oxygen
What useful features does an amoeba have for gas exchange?
Single cell - has a large SA:V ratio
The cell membrane is thin - diffusion into cell is rapid
Single cell is thin - short diffusion pathway within the cell
Why do multicellular organisms have respiratory systems?
They have a smaller SA:V ratio than smaller organisms meaning that diffusion across their surface is not efficient enough for their gas exchange.
What adaptation does a flatworm have to help with gas exchange?
Being flat they have a much larger surface area than a spherical organism of the same volume.
How can flatworms complete gas exchange through their outer surface?
No part of the body is far from the surface so the diffusion pathway is short.
What adaptations does an earthworm have to allow it to respire through its skin?
1) Cylindrical - has a large surface area to volume ratio
2) It keeps its respiratory surface moist by secreting mucus
3) Enough oxygen diffuses through skin because it is slow moving and has a low metabolic rate
4) Has a circulatory system to deliver oxygen to tissues (maintain diffusion gradient)
Why do multicelular organisms need more oxygen and to remove more carbon dioxide?
They usually have a higher metabolic rate
Why are the respiratory surfaces of multicellular organisms usually found on the inside of the body?
It can be easily damaged and this protects it
What are the major problems for terrestrial organisms?
1) Water evaporates from the body surfaces which could causes dehydration
2) Water molecules pass through gas exchange surfaces, so they are always moist but consequently they are going to lose a lot of water
How are lungs adapted to minimise water loss?
They are situated on the inside of the body (minimises heat and water loss)
What are the three main types of respiratory surface in animals?
Gills - in aquatic organisms
Lungs - these evolved in the terrestrial animal groups including birds, reptiles, mammals and adult amphibians
Tracheae - the air filled tubes in terrestrial organisms
What method do amphibians use to get enough oxygen to survive?
Their skin is moist with a well-developed capillary network below the surface. Gas exchange takes place through the skin and when the animal is active, through the lungs
How do reptiles get enough oxygen to survive?
Their lungs have a more complex internal structure than those of amphibians, increasing the surface area for gas exchange.
Why do mammals need a ventilation mechanism?
1) Have high metabolic rates
2) Maintains steep concentration gradient
3) more oxygen supplied to alveoli
