Chapter 3 — Reproduction in Living Organisms · Biology. These are 10 questions from the Magmo3 bank on this lesson, from easy to hard. Solve each one, then open "Show answer and explanation". Magmo3 has 40 questions on this lesson, each with an explanation.
The sac that holds the testes outside the body cavity is called the...
Correct answer: (B) Scrotum
Explanation: The scrotum is the sac that holds the testes and lies outside the body cavity.
The testis carries out two main functions, which are...
Correct answer: (A) Producing sperm and the hormone testosterone
Explanation: The testis produces sperm for reproduction and secretes the hormone testosterone, which is responsible for male characteristics.
Sperm formation in humans begins at the stage of...
Correct answer: (A) Puberty
Explanation: Sperm formation begins at puberty and continues throughout life.
Which hormones does the ovary secrete?
Correct answer: (B) Estrogen and progesterone
Explanation: The ovary secretes the hormones estrogen and progesterone, which are female hormones.
The middle piece of the sperm is packed with mitochondria in order to...
Correct answer: (A) Produce the energy needed for the tail's movement
Explanation: The mitochondria in the middle piece produce the energy the tail needs so that the sperm can move.
The head of the sperm contains the nucleus and...
Correct answer: (B) The acrosome
Explanation: The head of the sperm contains the nucleus and the acrosome, which secretes enzymes that help it penetrate the ovum.
Which cells secrete the hormone testosterone in the testis?
Correct answer: (C) The interstitial cells
Explanation: The interstitial cells that lie between the seminiferous tubules secrete the hormone testosterone.
What is the minimum number of secondary spermatocytes and of secondary oocytes needed to produce 120 sperms and 30 ova?
Correct answer: (A) 60 secondary spermatocytes and 30 secondary oocytes
Explanation: Each secondary spermatocyte divides by meiosis II into 2 spermatids, which become 2 sperms: 120 ÷ 2 = 60. Each secondary oocyte gives only one ovum (plus a polar body): 30 ova need 30 secondary oocytes.
One primary germ cell in a testis and one in an ovary each divide by mitosis three successive times in the multiplication phase, and every resulting cell then completes gametogenesis. How many sperms are produced, and how many polar bodies?
Correct answer: (A) 32 sperms and 24 polar bodies
Explanation: Three mitotic divisions give 2 × 2 × 2 = 8 spermatogonia and 8 oogonia, which grow into 8 primary spermatocytes and 8 primary oocytes. Each primary spermatocyte gives 4 sperms (8 × 4 = 32), while each primary oocyte gives one ovum and 3 polar bodies (8 × 3 = 24).
Semen analysis of two men gives these results. Man A: 15 million sperms per ejaculation, all with normal structure and movement. Man B: 400 million sperms per ejaculation with normal movement, but their heads lack acrosomes. Which conclusion is correct?
Correct answer: (A) Both men are likely to be infertile, but for different reasons
Explanation: A man is considered infertile if he has fewer than 20 million sperms per ejaculation, because many are lost on the way to the ovum. Man B's sperms lack the acrosome that secretes the hyaluronic enzyme dissolving part of the ovum's coat, so none of them can penetrate the ovum.
The first 10 questions in every subject are free, each with an explanation.