Question

Sperm enters the egg.
A. Animal pole
B. Vegetal pole
C. Micropyle
D. Megapyle

Answer 1

Hint: Inside a blastula, an embryo is split into two hemispheres: the animal pole and the vegetal pole, according to developmental biology. In comparison to the vegetal pole below it, the animal pole is made up of small cells that divide quickly. In comparison to the animal pole above it, the vegetal pole comprises huge yolky cells that divide slowly. The animal-vegetal axis begins to form before fertilization.

Complete explanation:
Option A: The nucleus is found in the animal pole area of the egg. As fertilization is the process where the \[2\] haploid gametes fuse to form a diploid zygote. The sperm infiltrates the egg from the animal pole after its aftermath with the corona radiata and the zona pellucida.
Hence, option A is correct.
Option B: In comparison to the animal pole above it, the vegetal pole comprises huge yolky cells that divide slowly. This disallows the entry of sperm. The vegetal pole is thought to differentiate into extraembryonic membranes such as the placenta in mammals and the chorion in birds, which protect and nourish the developing embryo.
Hence, option B is incorrect.
Option C: A micropyle is shaped at the anterior pole of the egg in insects, and it has a complex structure. It may be a single pore or a set of canals that are clustered together. Several follicle cells or nurse cells with protoplasmic prolongations towards the egg, around which the chorion is secreted, form the micropyle.
Hence, option C is incorrect.
Option D: In biology, the word megapyle does not mean anything. It does not exist. In the egg of the female, a megabyte means nothing.
Hence, option D is incorrect.

Hence, Option A is the correct answer.

Note:
Sperm can enter the animal hemisphere from either direction. The dorsoventral axis is defined by the point where sperm enters the body; cells opposite the point of sperm entry will gradually form the dorsal portion of the body. A pigment pattern in the frog Xenopus laevis gives the oocyte the appearance of a radially symmetrical body with distinct polarity. The vegetal hemisphere is only lightly pigmented, while the animal hemisphere is dark brown. The axis of symmetry moves through the animal pole on one side and the vegetal pole on the other.