All animals begin life as a _.

Explanation

All animals, from simple sponges to complex humans, begin their lives as a single fertilized egg cell, also known as a zygote. This zygote is formed when a sperm fertilizes an egg cell, resulting in a single cell with a unique combination of genetic material from both parents.From this single cell, the embryo develops through various stages, including:1. Cleavage: The zygote divides into multiple cells.2. Blastula: A hollow ball of cells forms.3. Gastrula: The blastula undergoes invagination, forming a multilayered embryo.So, while all animals do pass through the blastula and gastrula stages, they all begin life as a single fertilized egg.