What are the contributions of the following scientists to developing the Cell Theory? (Bio.lA. 2 Cell Theory) a. Schwann b. Hooke c. Schleiden d. Virchow ist the levels of organization and give an example of each from the human body. (Bio.lA.3 nulticellular organization)

### Contributions to Cell Theory 1. **Robert Hooke**: - **Contribution**: Hooke is credited with the discovery of cells. In 1665, he used a microscope to examine a thin slice of cork and observed small, box-like structures, which he called "cells." This was the first time the term "cell" was used in a biological context. - **Significance**: His work laid the foundation for the study of cells and their structure. 2. **Matthias Schleiden**: - **Contribution**: Schleiden, a botanist, proposed that all plants are made up of cells in 1838. He emphasized that the cell is the basic unit of life in plants. - **Significance**: His ideas contributed to the understanding that cells are fundamental to all living organisms, not just plants. 3. **Theodor Schwann**: - **Contribution**: Schwann, a zoologist, extended Schleiden's ideas to animals in 1839, stating that all animals are also composed of cells. He is known for co-formulating the cell theory alongside Schleiden. - **Significance**: Schwann's work helped establish the concept that cells are the building blocks of all living organisms. 4. **Rudolf Virchow**: - **Contribution**: In 1855, Virchow proposed that all cells arise from pre-existing cells, encapsulated in the phrase "Omnis cellula e cellula." This challenged the idea of spontaneous generation. - **Significance**: His contribution solidified the understanding that cell division is a fundamental process in the life cycle of cells. ### Levels of Organization in the Human Body 1. **Cell**: - **Example**: Red blood cell (erythrocyte) - responsible for transporting oxygen throughout the body. 2. **Tissue**: - **Example**: Epithelial tissue - forms protective layers on body surfaces and lines cavities. 3. **Organ**: - **Example**: Heart - a muscular organ that pumps blood throughout the body. 4. **Organ System**: - **Example**: Circulatory system - includes the heart, blood vessels, and blood, responsible for transporting nutrients and oxygen to cells and removing waste products. 5. **Organism**: - **Example**: Human being - a complete living entity made up of various organ systems working together to maintain life. These levels of organization illustrate the complexity of biological systems, from the simplest unit (the cell) to the entire organism.