Question

State whether true or false:
In non-mammalian species, there is no inner cell mass. Instead, the blastula consists of just one cell layer.

• A. True
• B. False

Answer 1

The correct option is A

True

The mitotic division (cleavage) starts in the zygote, which forms 2, 4, 8, and then 16 daughter cells called blastomeres. The embryo with 8 to 16 blastomeres is called a morula. The morula continues to divide, and transforms into a blastocyst. The blastomeres in the blastocyst are arranged into an outer layer called trophoblast and an inner group of cells attached to trophoblast called the inner cell mass. In non-mammalian species, there is no inner cell mass. Instead, the blastula consists of just one cell layer. However, because mammalian embryos have to attach to the uterine wall, they form a specialized type of blastula called a blastocyst. ​