OCR GCSE Biology Practice Exam 2025 – Comprehensive All-in-One Guide to Exam Success

Body tissues are primarily formed by stem cells, which are unique because they have the ability to differentiate into various specialized cell types. Stem cells can develop into muscle cells, nerve cells, blood cells, and other types of cells, making them fundamental for growth, development, and healing in multicellular organisms. Their versatility allows them to replenish tissues and contribute to the overall cellular architecture of the body.

Gametes, such as sperm and eggs, are primarily involved in reproduction rather than the formation of tissues. Zygotes, which are formed when a sperm cell fertilizes an egg, are the earliest stage of development in multicellular organisms but rely on stem cells to develop into the different tissues in the body. Sperm cells, while essential for reproductive processes, do not participate in forming body tissues themselves. Thus, stem cells are recognized for their critical role in tissue formation.