biology: working as a biologist
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- mag= size of diagram
- real size
- mag= size of image
- size of object
mag= eye piece X objective
- - Scanning: 3D image
- - Transmisson: internail detail
- (SEM + TEM)
- When magnification increases the field of view goes down.
- - Compund: two seperate lens stystems, one for each eye. Shows small body in 3D (e.g. ant)
- - Compound: two or more seperate lenses. Shows interal structure of cells.
Surface area to volume ratio
SA:V - number of units of surface area. E.g. as the organism gets bigger the ratio or surface area to volume gets smaller.
Exchange of materials across membranes
- Osmosis: movement of water across a semi permeable membrane from a high concentration to a low concentration.
- E.G. cell membrane will allow water but not salt.
Diffusion: molecules of solute spread from areas of low concentration in the solvent.
- Solvent: substance that dissolves the solute into it.
- Solute: substance that is dissolved into the solvent.
- E.G. water (solvent) will have salt dissolve into it (solute).
Hypotonic: less solute (salt) molecules outside the cell, which causes the water to be sucked in that direction. E.G. the cell will gain water and grow larger.
Hypertonic: more solute (salt) molecules outside the cell, which causes the water to be sucked in that direction. E.G. the cell will shrink and may die.
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