- Created by: Megan Lewsley
- Created on: 10-03-18 17:56
3A.1 Size & Surface Area
Exchange of Substances with the Environment
- Every organism needs to exchange substances with it's environment, no matter what size it is.
- Every organism needs oxygen and nutrients for respiration and create waste products such as carbon dioxide and urea, that need to be removed.
- Most organisms need to remain at the same temperature, so heat is exchanged as well.
Surface Area : Volume Ratio
- Surface area : volume ratio affects how quickly substances are exchanged.
- Smaller organisms have a higher surface are : volume ratio than larger organisms.
Exchange Organs in Single-celled Organisms
- All organisms need to be supplied with substances for respiration and have waste substances removed.
- These substances can diffuse directly into & out of the cell across the cell membrane.
- Diffusion rate is quick because of a short diffusion pathway (distance needed to travel).
Energy Organs in Multicellular Organisms
- Diffusion across the outer membranes is too slow because:
- 1. Cells are too deep in the body, there is a large distance between them and…