Question:

Holoblastic cleavage with almost equal-sized blastomeres is a characteristic of placental animals. Eggs of most mammals, including humans, are of centrolecithal type.

Updated On: Jul 28, 2022
  • If both Assertion and Reason are true and the reason is the correct explanation of the assertion
  • If both Assertion and Reason are true but the reason is not the correct explanation of the assertion
  • If Assertion is true statement but Reason is false
  • if both Assertion and Reason are false statements
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The Correct Option is C

Solution and Explanation

In holoblastic cleavage, the cleavage furrows bisect the entire egg, or in other words, entire egg divides by each cleavage furrow. In placental mammals having isolecithal or microlecithal egg, the holoblastic cleavage produces blastomeres of equal or approximately equal size. Centrolecithal eggs are found in insects and in some hydrozoa. Here, yolk is concentrated at the centre of egg and the cytoplasm is present surrounding it. Meroblastic cleavage occurs in them.
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Concepts Used:

Human Reproduction

Reproduction in human beings involves the fusion of male and female gametes that produces in their reproductive system.

Male Reproductive System:

The male reproductive system comprises:

  • Testicles (testes): A pair of oval-shaped organs masked in a pouch known as the scrotum. They manage the production of sperms and the male hormone testosterone.
  • Scrotum: It is a sac-like organ that hangs under the penis and behind it. It is the house of the testes, or testicles, and maintains a temperature that is needed for the production of sperm by it.
  • Vas deferens: The sperms produced in testes are stored in a tube known as the epididymis. Here the sperms get matured and pass to the urethra via the muscular tube known as vas deferens.
  • Accessory glands: This includes three glands, namely the prostate gland, seminal vesicles, and Cowper’s gland. The secretions from the mentioned three glands mix to form a fluid known as semen. Semen nourishes the sperm, raises the volume, and helps in lubrication.
  • Penis: The penis is a cylindrical tube that serves as both an excretory organ, and a reproductive organ. It transfers sperms into the vagina during sexual intercourse.

Female Reproductive System:

The female reproductive system is active before, during, and after fertilization as well. It comprises the following parts:

  • A pair of ovaries: A pair of ovaries produce and stores ovum in them. They also produce a female hormone known to be estrogen.
  • Fallopian tubes (Oviducts): They are the area of fertilization. They connect both the ovaries with the uterus.
  • Uterus: Uterus is the place of development for the embryo.
  • Vagina: The part that connects the cervix to the external female body parts is called a vagina. It is the passage for the penis during coitus as well as a fetus during transfer.