Exchange Between Organisms and Their Environment Flashcards
What is the difference between the internal and external environment of an organism?
The external environment surrounds the organism, whilst the internal environment includes the conditions within the organism and its cells
Where does the transfer of materials between an organism and its environment take place?
At exchange surfaces and across cell plasma membranes
How does the mass transport system help maintain diffusion gradients?
It continuously moves materials to and from exchange surfaces, ensuring efficient diffusion
Why is diffusion alone insufficient for material exchange in multicellular organisms?
Most cells are too far from exchange surfaces, so diffusion alone cannot supply or remove materials efficiently
What is the environment surrounding the cells of multicellular organisms called?
Tissue fluid
What system is responsible for distributing absorbed materials removing waste in multicellular organisms?
The mass transport system
How does an organism’s size and metabolic rate affect material exchange?
Larger and more metabolically active organisms require a greater exchange of materials and need a larger surface area to volume ratio
How do organisms with high metabolic rate adapt to meet their exchange needs?
They evolve specialised exchange surfaces and efficient transport systems
List four type of materials that must be exchanged between an organism and its environment (RG, N, EP, H)
- Respiratory gases (like carbon dioxide CO2 and oxygen, O2)
- Nutrients (like glucose, fatty acids, amino acids, vitamins, minerals)
- Excretory products (urea and carbon dioxide)
- Heat
What are the two main ways materials are exchanged between an organism and its environment?
Passively, which requires no metabolic energy and actively, which requires metabolic energy
What are the two passive processes involved in material exchange?
Why do these passive processes not require metabolic energy?
Diffusion and Osmosis
They rely on concentration gradients, moving substances from areas of higher concentration to lower concentration
What type of transport requires metabolic energy?
Active transport
Where does exchange take place in an organism?
At the surface of the organism
Why must the exchange surface be large compared with an organism’s volume?
The materials absorbed at the surface are used by the cells that makeup most of the organism’s volume
Why do small organisms not require specialised exchange surfaces?
They have a large surface area compared with their volume, allowing efficient exchange across their body surface
Why is simple diffusion insufficient for larger, more active organisms?
The outer surface cannot supply enough substances to meet metabolic demands so it would take too long for substances to diffuse to the centre of the organism
What happens to the surface area to volume ratio as organisms become larger?
Volume increases at a faster rate than surface area, reducing the surface area to volume ratio
What are two adaptations organisms have evolved to overcome limitations of diffusion?
1/ Flattened shapes - ensuring no cell is too far from the surface
2/ Specialised exchange surfaces - which increase the surface area to volume ratio
