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SS1: BIOLOGY - 2ND TERM

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  1. Cellular Respiration | Week 1
    5 Topics
    |
    1 Quiz
  2. Excretion & Growth in Living Cells | Week 2
    4 Topics
    |
    1 Quiz
  3. Irritability | Week 3
    6 Topics
    |
    1 Quiz
  4. Reproduction of Organisms | Week 4
    5 Topics
    |
    1 Quiz
  5. Tissues and Supporting Systems | Week 5
    6 Topics
    |
    1 Quiz
  6. Animal Nutrition | Week 6
    6 Topics
    |
    1 Quiz
  7. Enzymes | Week 7
    1 Topic
    |
    1 Quiz
  8. Heterotrophic Nutrition | Week 8
    3 Topics
    |
    1 Quiz
  9. The Mammalian Dentition | Week 9
    3 Topics
    |
    1 Quiz
  10. Basic Ecological Concepts | Week 10
    3 Topics
    |
    1 Quiz
  11. Local Biotic Communities | Week 11
    4 Topics
    |
    1 Quiz
  12. Major Biomes of the World | Week 12
    5 Topics
    |
    1 Quiz



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1a. State four differences between asexual and sexual reproduction.

b. Explain the term vegetative propagation.

c. List five methods of natural propagation.

d. List five methods of artificial propagation.

2a. Outline the process of conjugation in Spirogyra.

b. What is meiosis?

c. Outline the main events that occur in the first and second meiotic divisions.

d. What is the difference between meiosis and mitosis?

e. State three biological significance of meiosis.

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Evaluation Questions

1a. State four differences between asexual and sexual reproduction.

Answer:

Asexual Reproduction Sexual Reproduction
Does not involve gametes or sex cells. Involves the fusion of gametes.
Offspring are genetically identical. Offspring are genetically different from each other.
Involves only one parent individual. Involves two parents.
Asexual reproduction is faster and produces more offspring at a time. Sexual reproduction is not as fast as asexual reproduction and produces fewer offspring at a time.

 

c. List five methods of natural propagation.

Answer:

Five methods of the natural propagation of plants are by using the following parts: Bulbs, Corms, Rhizomes, Suckers, Stem cuttings, and Stem tubers.

 

d. List five methods of artificial propagation.

Answer:

Five artificial methods of vegetative propagation methods are Budding, Grafting, Cuttings, Marcotting, and Layering.

 

2a. Outline the process of conjugation in Spirogyra.

Answer:

This involves the following steps:

  • Two filaments called conjugants lie side by side
  • Lateral outgrowths develop on the adjacent cell of each conjugant.
  • The outgrowths meet and the walls dissolve to form a conjugation tube.
  • The male gametes from a conjugant migrate into the other conjugant and fuse with the female gametes.
  • Thick-walled zygospores are formed.
  • The zygospores germinate into new spirogyra filaments.

 

b. What is meiosis?

Answer:

Meiosis is the type of cell division that gives rise to gametes and haploid spores it takes place in the sex organs.

 

c. Outline the main events that occur in the first and second meiotic divisions.

Answer:

First Meiotic division

Prophase I

  • Chromatin threads coil and shorten to become chromosomes
  • Homologous chromosomes pair up
  • Their chromatids touch and crossing over or exchange of genetic materials takes place.
  • Nuclear envelope and nucleolus disappear as spindle fibres form.

Metaphase I

  • The homologous pair of chromosomes arrange themselves at the middle of the cells.

Anaphase I

  • The chromosomes separate from each other and move to the opposite poles of the cell.

Telophase I

  • Nuclear membrane form around the chromosomes
  • Cytoplasm constricts and cell division follows
  • Two daughter cells with half the number of chromosomes

Second Meiotic division

Prophase II

  • Centrioles move to the opposite poles of the cell
  • Nuclear envelope breaks down
  • Spindle fibres form

Metaphase II

  • The chromosomes arrange themselves along the middle of the cell on the spindle fibres

Anaphase II

  • Each chromosome splits into two and moves to the opposite poles of the cell

Telophase II

  • Spindle fibres disappear
  • Nuclear envelope forms
  • Cytoplasm divides to form four daughter cells each with half the chromosome number of the parent cell.

 

d. What is the difference between meiosis and mitosis?

Answer:

Meiosis Mitosis
Occurs during the formation of sex cells Occurs during growth and asexual reproduction
Four daughter cells are formed Two daughter cells are formed.
Chromosome numbers of parent and daughter cells are not the same, that of daughter cells is half that of the parent. Chromosome numbers of parent and daughter cells are the same.

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