- What is the smallest unit of LIFE? Cells.
- What does biogenesis mean? The idea that living organisms can only come from other living organisms.
- What does spontaneous generation mean? The idea that living organisms could spontaneously come from non-living things.
Scientists support the concept of biogenesis.
The Cell theory is the biological concept that all living things are made out of cells. The six parts of it:
- All living things are composed of one or more cells (Unicellular or Multicellular).
- Cells are the basic unit of structures and functions of all living things.
- All cells come from pre-existing cells and contain DNA that is passed from cell to cell during cell division.
- Cells contain specialized structures to perform functions necessary for life.
- Cells have the same basic chemical composition in organisms of similar species.
- Energy flow occurs within cells.
The cell theory helps define what a living organism is, explains the relationship between cells and living organisms and supports biogenesis, the scientific concept that states that all living organisms come from other living organisms.
- Francesco Redi is an Italian scientist who, in the 1600s, set out to disprove the scientific concept of spontaneous generation. He performed experiments with meat and maggots in jars--in order to prove the idea that meat, a non-living thing, cannot spawn living organisms, maggots.
- Lazzaro Spallanzani is another Italian scientist who performed experiments with meat broth in flasks--in order to disprove the scientific concept of spontaneous generation. His experiments showed that meat broth can't generate microbes or bacteria.
- Louis Pasteur is a world-renowned French biologist who performed experiments with meat broth in swan-necked flasks. Did the same thing as Spallanzani; disproved spontaneous generation.
- Robert Hooke is a 1600s Englishman scientist who looked at cork from a plant (under a microscope) and coined the term, "cell", since he saw rigid cell walls. See Lesson 1 on the course, "High School Biology".
- Antonie van Leeuwenhoek is a 1600s Dutch scientist/merchant who examined samples of pond water, plant material, and other things under the microscope. He developed the earliest form of the microscope and made it popular due to his drawings of animalcules.
- Robert Brown discovered the cell nucleus in 1833.
- Matthias Schleiden discovered that all plants were made out of cells (1838).
- Theodore Schwann discovered that all animals were composed of cells (1839).
- Rudolf Virchow concluded that new cells could only come from the divisions of existing cells (1858).