Organism A living thing. Observation Gathering information in a careful, orderly way. Data Information gathered from observations. Inference A conclusion based on experience or evidence. Hypothesis A proposed explanation for observations.
DESIGNING AN EXPERIMENT Asking a question Forming a hypothesis Doing a controlled experiment Recording and analyzing results Drawing a conclusion
An EXPERIMENT… Can make a discovery. Can test a hypothesis. Can prove a known fact.
Example: how do organisms come into being? In the past, observations showed that some living things just appeared. Mice appeared in grain. Maggots appeared on meat.
People thought that the mice came from the grain, and the maggots came from the meat. This idea was called spontaneous generation. Do you think spontaneous generation is correct?
A doctor named Redi had a different idea. He observed that maggots appeared on meat a few days after flies were around it. His hypothesis was that flies made the maggots.
A hypothesis is a possible explanation based on observations and evidence. All experiments begin with a hypothesis.
Remember: an experiment tests a hypothesis. Redi wanted to test his hypothesis. He had to figure out which variable to change. A variable is any part of the experiment that can change. For example: equipment, material, temperature, light, time. An experiment should only change 1 variable at a time. The variable that the scientist changes is called the manipulated variable. The variables that change as a result of the manipulated are called the responding variables.
Here is Redi’s controlled experiment. What are the controlled variables? What are the manipulated variables? What are the responding variables?
Controlled variables: jars, type of meat, location, temperature, time. Manipulated variables: closing the jars Responding variable: maggots
Redi observed that maggots appeared on the meat in the open jars. No maggots appeared on the meat in the closed jars. He recorded his findings by writing them down for future scientists.
The conclusion uses evidence from the experiment to state if the hypothesis was supported or refuted. Supported = hypothesis was correct. Refuted = hypothesis was incorrect. Was Redi’s hypothesis supported or refuted? What was his conclusion?
Redi’s hypothesis was SUPPORTED. His conclusion: flies produce maggots. Spontaneous generation is incorrect. New organisms come from existing organisms. This is called biogenesis.
If a hypothesis is supported by many different experiments, it can become a theory. A theory is a well-tested explanation that brings many observations together. Theories let scientists make better predictions about new situations. Sometimes more than one theory is needed to explain something. For example…
…kangaroos and koalas!Oy mate. G’day Why are they only in Australia?
The answer can be explained by 2 theories: Evolution (more later in this class) Plate tectonics (more later in Physics)
Plate Tectonics Millions of years ago, Australia, Antarctica and South America were all joined in one continent. This continent broke apart, and Australia became a continent by itself. Evolution Organisms change over time to survive. Since Australia was so far away from other continents, the animals in Australia changed in unique ways