Chapter 7 Flashcards
Why don’t unicellular organisms not require specialised exchange surfaces?
- Small diffusion distance
- Low metabolic activity
- Large SA:V
Why does low metabolic activity in unicellular organisms mean that they don’t require specialised exchange surfaces?
Oxygen demands and carbon dioxide production is low
Why do unicellular organisms have a small diffusion distance?
Distance between cell surface membrane and inside of cell is very small so simple diffusion is used
Why do multicellular organisms require specialised exchange surfaces?
- large diffusion distance
- small SA:V ratio
- high metabolic activity
Why do multicellular organisms have a larger diffusion distance?
oxygen has to travel very far to oxygen demanding cells
Why do multicellular organisms have a smaller SA:V ratio?
- made up of many cells arranged in tissues, organs, and organ systems so inefficient and insufficient exchange with just simple diffusion
Why do multicellular organisms have a higher metabolic activity?
oxygen demands and carbon dioxide production is very high
What do effective exchange surfaces have to include?
- increased SA
- thin layers
- good blood supply
- ventilation to maintain diffusion gradient
How does increasing SA make exchange surfaces effective?
- provides area needed for exchange
- overcomes limitations of SA:V of larger organisms
- eg. root hair cells, villi
How does thin layers make exchange surfaces more effective?
- short diffusion distance
- makes it fast and efficient
- eg. alveoli, villi
How does good blood supply make exchange surfaces more effective?
- steeper gradient means faster diffusion
- ensures substances constantly delivered to/removed from exchange surface
- eg. alveoli, gills villi
How does ventilation make exchange surfaces more effective?
- for gases - ventilation system helps to maintain concentration gradients
- makes process efficient
- eg. alveoli, gills
Why are gaseous exchange surfaces moist?
- oxygen dissolves in water before diffusing into tissues
- conditions needed to take in oxygen successfully also ideal for evaporation of water
Why do mammals have a high metabolic rate?
- active + maintain own body temperature (independent of environment)
- needs lots of oxygen - cellular respiration which produces lots of carbon dioxide (removed)
- process occurs in lungs
What are the key structures of the human exchange system?
- nasal cavity
- trachea
- bronchus
- bronchioles
- alveoli
What is function of the nasal cavity?
- large SA and good blood supply which warms air to body temp
- hairy lining which secretes mucus (traps dirt and bacteria) which protects lung tissue from irritation + infection
- moist surface which increases humidity of incoming air which reduces evaporation from exchange surfaces
What is the function of the trachea?
- main airway carrying clean, warm, moist air from nose to chest
What is the structure of the trachea?
- wide tube supported by incomplete (allows food to move down oesophagus) rings of string flexible cartilage (stops from collapsing)
- lined with ciliated epithelium
