As a fertilized human egg divides, it first becomes a solid ball of cells, the morula. Next, about five days after fertilization, it becomes a hollow ball, the blastocyst. The cells of the outer layer of the blastocyst eventually form part of the placenta.
Not all animals that lay eggs lay them in nests.Birds and fish are not the only animals that lay eggs. Insects, turtles, lizards, and reptiles lay eggs, too. Only two mammals lay eggs: the platypus and the echidna.
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Answer:
As a fertilized human egg divides, it first becomes a solid ball of cells, the morula. Next, about five days after fertilization, it becomes a hollow ball, the blastocyst. The cells of the outer layer of the blastocyst eventually form part of the placenta.
Not all animals that lay eggs lay them in nests.Birds and fish are not the only animals that lay eggs. Insects, turtles, lizards, and reptiles lay eggs, too. Only two mammals lay eggs: the platypus and the echidna.
Explanation: