Biology 2201 The overview

The course consists of four units. They are as follows Matter and Energy for life (suggested time: 27 hours) Biodiversity (suggested time: 32 hours) Maintaining Dynamic Equilibrium I (suggested time: 42 hours) Interactions among living things (suggested time: 10 hours)

Evaluation Scheme Tests – 30% Assignments/Labs/Presentations – 10% Midterm exam – 10% Final exam – 50%

Unit 1 – Matter and Energy for life Abiogenesis Vs. biogenesis Early scientists thought that living things could come from non-living things such as mud or raw meat. This belief is referred to as abiogenesis or spontaneous generation. Biogenesis is a theory that states that living things can only be produced by other living things. This is the theory that is accepted by scientists today.

The theory of Abiogenesis was discredited over time by a number of scientists. Some were 1. Aristotle (334 B.C.) – Classified all organisms as plants and animals. He believed that living things could arise from non-living things.

2. Francesco Reddi (1660) – Using proper scientific methods, he did experiments using maggots. The observed that after flies landed on rotting meat, maggots formed. Then these maggots gave rise to more flies. His experiment consisted of two jars, both containing rotting meat. He covered one of the jars and left the other open. He showed that no flies appeared on the meat that was not accessible to the flies.

3. John Needham (1748) – Believed in abiogenesis 3. John Needham (1748) – Believed in abiogenesis. He had observed that microscopic organisms lived in meat broth. He also observed that they died when the broth was boiled. His experiment consisted of: Boiled two containers of meat broth containing microorganisms He then covered one of them and not the other. He found that microorganisms grew in both containers

4. Lazzaro Spallanzani (late 1700’s) - Retested Needham’s experiment 4. Lazzaro Spallanzani (late 1700’s) - Retested Needham’s experiment. He realized that Needham had not boiled the broth long enough to kill all the microorganisms. He recreated Needham’s experiment but he boiled the broth for over an hour. He sealed some of the flasks by melting the necks shut to make and air-tight seal. He found that microorganisms grew in the open flasks but not in the closed ones. Upon opening the closed ones living organisms appeared within hours. Supporters of spontaneous generation believed that by sealing the flask he killed on vital principle that was contained in the air.

5. Louis Pasteur (1860) – He placed broth in long neck flasks and then heated the neck of the flask to form an “S” shape. He then boiled the contents of the flask. - the S neck kept our organisms and so none grew in the sanitized broth. - Pasteur finally had proven that spontaneous generation did not exist. Supporters of the theory could no longer come up with any plausible explanation.