Cell theory
- According to cell theory, living organisms are composed of cells.
- Organisms consisting of only one cell carry out all functions of life in that cell, e.g. Paramecium, Chlorella.
- Identifying the characteristics of living things (Mr H. Gren - metabolism, response, homeostasis, growth, reproduction, excretion & nutrition).
- Surface area to volume ratio is important in the limitation of cell size.
- Multicellular organisms have properties that emerge from the interaction of their cellular components, (Emergent properties).
- Specialised tissues can develop by cell differentiation in multicellular organisms.
- Differentiation involves the expression of some genes and not others in a cell.
- Stem cells can divide and differentiate along different pathways in embryonic development which makes stem cells useful for therapeutic uses (e.g. Stargardt's disease).
- There are ethical concerns about the use of embryo stem cells.
Calculating magnification and size
- Calculate the magnification of an electron microscope image from a scale bar.
- Calculate specimen size using a scale bar.
- Calculate specimen size using magnification.