1: Cell Theory

Question 1

What are the three tenets of the cell theory?

Answer 1

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

Question 2

What do all cells consist of? What is usually found in plant and animal cells?

Answer 2

1. a cytoplasm enclosed by a plasma membrane

2. a nucleus that contains genes

Question 3

Draw a human cheek cell.

Answer 3

1. plasma membrane
2. cytoplasm
3. nucleus
4. mitochondria

Question 4

Draw a moss leaf cell.

Answer 4

1. cell wall
2. plasma membrane
3. cytoplasm
4. chloroplasts
5. sap in vacuole
6. nucleus
7. vacuole membrane

Question 5

How was the cell theory developed?

Answer 5

scientists noticed a trend for living organisms to be composed of cells

Question 6

How can scientific theories be tested?

Answer 6

by looking for discrepancies - cases that don’t fit the theory

Question 7

Name three organisms that do not fit the cell theory.

Answer 7

1. skeletal muscle
2. giant algae
3. aseptate fungi

Question 8

Why does skeletal muscle not fit the cell theory?

Answer 8

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)

Question 9

Why does giant algae not fit the cell theory?

Answer 9

1. can grow to 100mm but are not multicellular (doesn’t fit) since they only contain one nucleus, rather than hundreds of nuclei

Question 10

Why does aseptate fungi not fit the cell theory?

Answer 10

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)

Question 11

If there are discrepancies in the cell theory, why hasn’t it been abandoned?

Answer 11

1. there is still a strong overall trend

Question 12

What are the 7 characteristics needed for a thing to be classed as alive?

Answer 12

Movement: Living things show movement, either externally or internally
Reproduction: Living things produce offspring, either sexually or asexually
Sensitivity: Living things can respond to and interact with the environment
Growth: Living things can grow or change size / shape
Respiration: Living things use substances from the environment to make energy
Excretion: Living things exhibit the removal of wastes
Nutrition: Living things exchange materials and gases with the environment