1. State what is meant by cell theory and give evidence to support it (4)
Living things are made from cells
Cells are the smallest living units
Cells are the building blocks of life
Cells can survive on their own- organelles can not
Cells divide by mitosis
Viruses require a host cell
Evidence-Organisms appear to be made of cells when viewed under a light microscope

2. Explain how single celled organisms contradict cell theory and explain why these organisms have limited growth (5)
Organisms made from only one cell
Can still carry out all the characteristics of life
Fungal hyphae and skeletal muscle can be multinucleated
Diffusion/osmosis effective only over short distances
As volume increases surface area for diffusion decreases
Refer to surface area to volume ratio

3. Explain why scientists think that Eukaryotes may have developed from Prokaryotes, how are the first cells believed to have come in to existence? (3)
Endosymbiotic theory- endocytosis of other cells e.g. cells attained organelles by engulfing/symbiosis other cells
All new cells are derived from existing cells
The first cells must have arisen from non-living material

4. What is meant by cell differentiation, how are cells able to differentiate and why is differentiation beneficial to the organism (4)
Specialisation of a cell
Multi-cellular organisms have cells which interact
Differentiated cells form tissues, organs and organ systems
Differentiation involves the expression of some genes and the switching off of others
No one cell needs to perform all characteristics of life
This removes the limitations of cell size