Exchange Between Organisms and Their Environment Flashcards
How can you compare the internal and external environments of organisms?
They are different
What must organisms do with their two environments to survive?
Transfer materials
Where does the transfer of materials across organisms environments take place?
At exchange surfaces
What do transferred materials cross at exchange surfaces?
Cell plasma membranes
What is the environment surrounding the cells of multicellular organisms called?
Tissue fluid
Where are materials distributed to after absorption in multicellular organisms?
Tissue fluid
How does the size and metabolic rate of an organism affect their surface area?
Organisms with a high metabolic rate will exchange more materials therefore will require a larger surface area to volume ratio
Give examples of respiratory gases that need to be interchanged between an organism and its environment
Oxygen and carbon dioxide
Give examples of nutrients that need to be interchanged between an organism and its environment
Glucose, fatty acids, amino acids, vitamins and minerals
Give examples of excretory products that need to be interchanged between an organism and its environment
Urea and carbon dioxide
How does the interchange of respiratory gases, nutrients and excretory products between an organism and its environment take place?
- Passively by diffusion and osmosis
- Actively by active transport
What does active transport require?
Metabolic energy
In larger organisms what type of surface area to volume ratio is needed?
A large one
Why do some organisms have a flattened shape?
So no cell is ever far from the surface
Why do some organisms have specialised exchange surfaces?
To increase their surface area to volume ratio
What are the features of a specialised exchange surfaces?
- They have a large surface area to volume ratio
- They are very thin to lower diffusion distance and increase diffusion rate
- They are selectively permeable to allow selected materials to cross
- Their environmental medium is constantly moving to maintain a diffusion gradient
- A transport system to ensure internal medium is constantly moving to maintain a diffusion gradient
What can happen as a result of diffusion pathways being thin?
They can be damaged or dehydrated easily
Often, where are thin diffusion pathways found?
Inside the body to protect them
Name four general things that need to be exchanged between organisms and their environment
- Respiratory gases
- Nutrients
- Excretory products
- Heat
Name 3 factors that affect the rate of diffusion of substances into cells
- Surface area
- Thickness of cell surface membrane
- Permeability of cell surface membrane to the substance
- Concentration gradient of substance between the inside and outside of the cell
- Temperature
