IGCSE Biology Paper-3: Specimen Questions with Answers 305 - 306 of 358

Passage

The diagram shows the male reproductive system.

Using a Label Line

Question 305 (1 of 2 Based on Passage)

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Describe two secondary characteristics regulated by testosterone.

Explanation

Secondary sexual characteristics are those sexually dimorphic characteristics that are not directly involved in reproduction. For males, secondary characteristics include facial and chest hair, increased body hair, pelvic build (lack of rounded hips) , upper body muscular build, and the ability to generate muscle mass at a faster rate than the female. For females, secondary sex characteristics include relative lack of body hair, thicker hair on the head (in some cases) , rounded hips/figure, a decreased ability to generate muscle mass at a fast rate, decreased upper body strength, breasts, ability to nurse children, a menstrual cycle, and increased body fat composition.

Question 306 (2 of 2 Based on Passage)

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Choose words from the list to complete each of the spaces in the paragraph. Each word may be used once only and some words may not be used at all.

Gametes are formed by the division of a nucleus, a process called … This process produces a total of … cells from the original cell. Each of these cells has a nucleus described as being … and each nucleus contains … the number of chromosomes present in the original nucleus.

Explanation

Gametes are formed by the division of a nucleus, a process called meiosis. This process produces a total of four cells from the original cell. Each of these cells has a nucleus described as being haploid and each nucleus contains half the number of chromosomes present in the original nucleus.

Significance of Meiosis

  • Meiosis form gametes that are required for sexual reproduction.
  • Meiosis maintains the fixed number of chromosomes in sexually reproducing organisms by having the same during gametogenesis.
  • In meiosis, paternal and maternal chromosomes assort independently. It causes a reshuffling of chromosomes and the traits controlled by them. The variations help the breeders in improving the races of useful plants and animals.
  • Meiosis introduces a new combination of traits or variations.
  • Chromosomal and genomic mutations occur by irregularities of meiotic division. Some of these mutations are useful to the organism.

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