Bio topic 1

Question 1

1a. [2 marks]

State processes occurring during interphase.

Answer 1

DNA replication (during S phase)
G1 growth and metabolism
G2 growth and preparation

Question 2

1b. [1 mark]

Using the letter C, label the stage on the diagram where chromosome supercoiling occurs.

Answer 2

Prophase

Question 3

1c. [1 mark]

Using the letter M, label the stage on the diagram where sister chromatids migrate to opposite poles.

Answer 3

Anaphase

Question 4

1d. [2 marks]

Distinguish between the outcomes of a cell dividing either by mitosis or meiosis.

Answer 4

Mitosis result into two identical daughter cells;

Meiosis result in four sex cells.

Question 5

1e. [1 mark]
The mitotic index is an important prognostic tool for predicting the response of cancer cells to chemotherapy. Outline how the mitotic index is calculated.

Answer 5

Mitotic index = # of cells in miosis/Total number of cells.

Question 6

2a. [4 marks]
The structure of prokaryotic cells has been investigated using electron microscopy. Draw a labelled diagram to show prokaryotic cell structure.

Answer 6

• Cell Wall
• Cell Membrane
• Pilus
• Plasmid

Question 7

2b. [7 marks]

Discuss the cell theory and its limitations.

Answer 7

Cell theory
1. Living organisms are composed of cells (or cell products)
2. The cell is the smallest unit of independent life
3. Cells can only arise from pre-existing cells
Limitations
• Striated muscle – composed of fused cells that are multinucleated
• Giant algae – unicellular organisms that are very large in size (~7 cm)
• Aseptate hyphae – lack partitioning and have a continuous cytoplasm

Question 8

3a. [4 marks]

Draw a labelled diagram to show the fluid mosaic model of the plasma membrane.

Answer 8

k

Question 9

3b. [4 marks]

Unicellular and multicellular organisms share the same functions of life. Outline four functions of life.

Answer 9

• Metabolism
• Reproduction
• Sensitivity
• Homeostasis

Question 10

3c. [7 marks]
The structure of organisms is based on organic molecules containing carbon. Explain the cycling of carbon in an ecosystem.

Answer 10

Autotrophs convert carbon dioxide into carbohydrates and other carbon compounds;

In aquatic ecosystems carbon is present as dissolved carbon dioxide and hydrogen carbonate ions;

Carbon dioxide diffuses from the atmosphere or water into autotrophs;

Carbon dioxide is produced by respiration and diffuses out of organisms into water or the atmosphere;

Methane is produced from organic matter in anaerobic conditions by methanogenic archaeans and some diffuses into the atmosphere or accumulates in the ground;

Methane is oxidised to carbon dioxide and water in the atmosphere;

Peat forms when organic matter is not fully decomposed because of acidic and/or anaerobic conditions in waterlogged soils.

Question 11

4a. [3 marks]

Describe how Pasteur’s experiments provided convincing evidence to falsify the concept of spontaneous generation.

Answer 11

Water in a flask was boiled.
When sealed after boiling, no growth occurs.
When unsealed, growth of bacteria occurs.

Question 12

4b. [1 mark]
State the function of life in Paramecium that is carried out by:
cilia.

Answer 12

Sensitivity

Question 13

4c. [1 mark]
State the function of life in Paramecium that is carried out by:
the contractile vacuole.

Answer 13

Excretion

Question 14

4d. [3 marks]
Discuss the advantages and disadvantages of the use of adult stem cells.
Advantages:

Answer 14

Advantages:
Low Tumor risk.

Disadvantages:
Very painful to extract;
Low growth potential.

Question 15

4e. [2 marks]

Explain the role of decomposers in an ecosystem.

Answer 15

Breaking down dead organic matter.

Recycle Nutrients within an ecosystem.