Video Transcript
Which of the following is not an
adaptation of egg cells? (A) They are haploid and thus
contain half the genetic material of a normal body cell. (B) The cytoplasm contains a large
volume of nutrients to help the embryo grow. (C) They are lined with cilia that
helps move substances away. (D) They have a protective jelly
coat that hardens after fertilization. (E) The egg cell membrane can fuse
with the sperm cell membrane.
The egg cell is the female
reproductive cell in humans. It is produced by the ovaries and,
if fertilized by a sperm, it will form an embryo and eventually a fetus. Let’s discuss some of the
adaptations of an egg cell to determine which of our answer choices is correct.
Both the egg and sperm cell are
haploid and contain half the genetic material of a normal body cell. This allows for a complete set of
chromosomes when the two cells combine and form an embryo. So we can eliminate answer (A)
because this is an adaptation of egg cells.
During fertilization, the sperm
cell membrane fuses with the egg cell membrane, allowing the sperm cell’s nucleus to
enter the egg cell. So we can eliminate answer choice
(E).
Once the egg has been fertilized by
a sperm cell, it needs to prevent further fertilization attempts. To do this, it has a jelly coat on
its outer surface that immediately hardens after fertilization. This prevents other sperm from
fertilizing the egg. So we can eliminate answer (D).
Finally, the egg cell has a large
volume of cytoplasm that contains nutrients to help the embryo grow. So we can eliminate answer (B).
Cilia are hairlike structures on
the surface of some cells, such as epithelial cells of the digestive tract. However, they are not found on egg
cells. So answer (C) is not an adaptation
of egg cells and is therefore the correct answer. They are lined with cilia that
helps move substances away.