Differentiate between morula and blastula of mammals.

Explanation

### Step-by-Step Solution:

1. **Definition of Morula**:
- The morula is an early stage of embryonic development that occurs after several rounds of cell division (cleavage) of the zygote. It is characterized by a solid ball of cells.
- Specifically, the morula consists of 16 cells, which is the result of the zygote undergoing multiple mitotic divisions.

2. **Definition of Blastula**:
- The blastula is a later stage of embryonic development that follows the morula stage. It is characterized by the formation of a hollow sphere of cells.
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