Flashcards in 1: Cell Theory Deck (12):
What are the three tenets of the cell theory?
1. cells are the smallest possible units of life
2. all living organisms are made of cells
3. all cells come from pre-existing cells
What do all cells consist of? What is usually found in plant and animal cells?
1. a cytoplasm enclosed by a plasma membrane
2. a nucleus that contains genes
Draw a human cheek cell.
1. plasma membrane
Draw a moss leaf cell.
1. cell wall
2. plasma membrane
5. sap in vacuole
7. vacuole membrane
How was the cell theory developed?
scientists noticed a trend for living organisms to be composed of cells
How can scientific theories be tested?
by looking for discrepancies - cases that don't fit the theory
Name three organisms that do not fit the cell theory.
1. skeletal muscle
2. giant algae
3. aseptate fungi
Why does skeletal muscle not fit the cell theory?
1. made up of muscle fibres which are enclosed in a membrane (fits)
2. but they are much larger than most cells - 300mm+ (doesn't fit)
3. and they contain hundreds of nuclei (doesn't fit)
Why does giant algae not fit the cell theory?
1. can grow to 100mm but are not multicellular (doesn't fit) since they only contain one nucleus, rather than hundreds of nuclei
Why does aseptate fungi not fit the cell theory?
1. consists of thread like structures called hyphae
2. hyphae not divided up into subunits by plasma membrane
3. but consist of long undivided sections which contain many nuclei (doesn't fit)
If there are discrepancies in the cell theory, why hasn't it been abandoned?
1. there is still a strong overall trend