Unit 1: Chapter 1 Matter and Energy For Life

Cell Theory All living organisms are composed of one or more cells Cells are the basic units of structure and function in all organisms All cells are derived (come from) pre- existing cells (biogenesis) In a multicellular organism, the activity of the entire organism depends on the total activity of its independent cells.

12 Scientists and Development of the Cell Theory For hundreds of years a debate raged amongst scientists, about the origin of living things. The debate centered around two theories: Abiogenesis Biogenesis Onion skin cells Paramecium

What is abiogenesis? Abiogenesis is the idea that living organisms can arise from non-living matter. It is also called Spontaneous Generation Thomas Huxley

Examples of abiogenesis: Appearances of mushrooms on logs Maggots forming on rotting meat Frogs and salamanders suddenly appearing on or in mud

What scientists supported abiogenesis? 1. Aristotle (384-322 B.C.E.) classifies all organisms into 2 kingdoms: plants and animals. He believed all living organisms can only arise from non-living matter.

2. John Needham (1713-1781) He believed microorganisms appeared in a sterilized flask of meat broth

He placed broth into a bottle, heated the bottle to kill anything inside, then sealed it. Days later, he reported that life had been created from nonlife. BUT! He did not heat the broth long enough to kill all the microbes.

What is biogenesis? Biogenesis is the idea that living organisms can only come from other living things.

Which scientists supported biogenesis? 3. Francesco Redi (1629-1697) He made the first serious attack on abiogenesis. He performed an experiment to show that maggots will not appear on rotting meat if flies are kept away.

Francesco Redi’s Experiment See page 8 in textbook http://www.sumanasinc.com/webcontent/animations/content/scientificmethod.html

4. Spallanzani (1729-1799) He was skeptical of Needham’s experiment, so he did his own He boiled the broth for a longer period of time and he kept one of the bottles sealed. No life appeared in the sealed bottle

5. Louis Pasteur (1822-1895) He ended the debate on abiogenesis using a swan neck flask He designed an experiment to prove microbes do not just appear in sterilized meat broth. Instead, these microbes actually come from the air. http://bcs.whfreeman.com/thelifewire/conte nt/chp03/0302003.html

http://www. sumanasinc http://www.sumanasinc.com/webcontent/animations/content/scientificmethod.html

Paradigm Shift As a result of the debate over abiogenesis and biogenesis there was a change in the way that science viewed the “origins of life”. The cell theory was developed Cell Theory Video http://www.youtube.com/watch?v=dscY_2 QQbKU

Other Scientists that contributed to the development of the cell theory: 6. Robert Hooke (1665) using a primitive lenses to form a simple microscope, observes “empty room like apartments” in samples of once living tree bark and called it cells.

7. Anton van Leeuwenhoek (1667) designs more powerful microscopes and writes extensively about his observations of tiny living organisms.

8. Robert Brown (1831) observes a darker region in all cells near the center and named it the nucleus.

9. Mathias Jacob Schleiden (1838) writes, “All plants are made of cells”.

10. Theodor Schwann (1839) writes “All animals are made up of cells”.

11. Alexander Carl Henrich Braun (1845) wrote “the cell is the basic unit of life”.

12. Rudolph Virchow (1858) formulates the points of the cell theory.

The wacky history of cell theory – by Lauren Royal-Woods http://ed.ted.com/lessons/the-wacky- history-of-cell-theory

(*Important: please write!) Cell Theory All living organisms are composed of one or more cells Cells are the basic units of structure and function in all organisms All cells are derived (come from) pre- existing cells (biogenesis) In a multicellular organism, the activity of the entire organism depends on the total activity of its independent cells.

The cell theory song http://www.youtube.com/watch?v=KuJqqi ATlqw

Work: Review worksheet/handout on Scientists In class assignment on Scientists