**Biologist who proposed the cell theory along with Schwann:**

The biologist who proposed the cell theory along with Schwann is **Matthias Jakob Schleiden**. He was a German botanist who, along with Theodor Schwann, contributed significantly to the development of the cell theory.

**Explanation:**

The cell theory is one of the fundamental concepts in biology, stating that all living organisms are composed of cells, cells are the basic units of structure and function in living organisms, and new cells arise from pre-existing cells. This theory was proposed in the 1830s, and Schleiden and Schwann played crucial roles in its formulation.

**Matthias Jakob Schleiden:**

Matthias Jakob Schleiden was a German botanist who is best known for his work on plant cytology. He studied plant tissues and published his observations and conclusions in a book titled "Contributions to Phytogenesis" in 1838. In this book, Schleiden proposed that plants are made up of cells and that the cell is the basic unit of plant structure.

**Theodor Schwann:**

Theodor Schwann was a German physiologist who is best known for his work on animal tissues. He studied different types of animal tissues and published his findings in a book titled "Microscopic Investigations on the Accordance in the Structure and Growth of Animals and Plants" in 1839. In this book, Schwann proposed that animals are also composed of cells and that the cell is the basic unit of animal structure.

**Collaboration and Development of the Cell Theory:**

Schleiden and Schwann were colleagues and friends who shared their research findings with each other. They corresponded extensively and discussed their ideas on the similarities between plant and animal tissues. Based on their observations and discussions, they came to the conclusion that all living organisms are composed of cells and that the cell is the basic unit of structure and function.

Their collaborative work and ideas formed the foundation of the cell theory. Schleiden and Schwann's contribution to the development of the cell theory is significant, as it laid the groundwork for our understanding of the fundamental unit of life and revolutionized the field of biology.

In conclusion, Matthias Jakob Schleiden, along with Theodor Schwann, proposed the cell theory, which states that all living organisms are composed of cells and that cells are the basic units of structure and function. Their collaborative work was crucial in establishing the cell theory and revolutionizing the field of biology.

Matthias Jakob schleiden and Schwann proposed the cell theory. in 1838, schleiden, first proposed the idea that all plant consist of cells.A year later,in 1839, Schwann independently asserted that all animals and plants are made up of cells.