Understanding the Reliability of Scientific Knowledge in Evidence Evaluation

ESSENTIAL QUESTION: When new evidence is discovered, how can you determine if it is valid? When presented with new valid evidence, what effect will it have one existing scientific ideas? RELIABILITY OF SCIENTIFIC KNOWLEDGE SC.6.N.2.2 EXPLAIN THAT SCIENTIFIC KNOWLEDGE IS DURABLE BECAUSE IT IS OPEN TO CHANGE AS NEW EVIDENCE OR INTERPRETATIONS ARE ENCOUNTERED.

BELLRINGER In recent scientific history, the classification of protists has changed several times. They now have been regrouped to consider their development over time instead of simply by how they move or look. Which statement best describes such changes in scientific knowledge? a) An entire species must be discovered before a classification system can be made. b) Early ideas about taxonomy should be unchallenged so that scientists can continue to classify new species. c) Modern technology and processes make it possible to prove an idea so further research is not necessary. d) As more knowledge is gained about organisms and natural events, scientific interpretations change as necessary.

I DO GUIDED NOTES

EVALUATING EVIDENCE In order for scientific knowledge to change, reliable evidence must be presented and evaluated. After much discussion and debate, scientific knowledge can be changed if the evidence is valid.

CONSISTENT: The results of repeated observations and/or experiments are reasonably the same when replicated by reliable investigators. The evidence is also compatible with well established observations and limits. Example: Green plants will grow towards a light source. Walking under a ladder will cause bad luck.

OBSERVABLE: The event, or evidence of the event can be observed and explained. Observations are limited to basic human senses and technology that extends our senses (microscopes). Example: Some plants eat meat. Aliens have visited Earth.

NATURAL: A natural cause must be used to explain why or how the naturally occurring event happens. Supernatural explanations cannot be tested and are, therefore outside of the realm of science. Example: Green plants convert sunlight into energy. Magicians can make humans, cars and rabbits disappear.

PREDICTABLE: The natural cause (mechanism) of the naturally occurring event can be used to make specific predictions. Each prediction can be tested to determine if it is true or false. Example: Without sunlight (or comparable artificial light) green plants will die. If you are a Scorpio, and your horoscope tells You that you will become rich , then you will win the lottery.

TESTABLE: The cause of the naturally occurring event must be testable through the process of science and controlled experiments. Supernatural events cannot be tested for validity. Example: Life comes from life and cannot come from non-living things. The Bermuda Triangle causes ships to sink and planes to disappear.

TENTATIVE: Scientific theories are subject to revision and correction. Scientific theories have been and will continue to be modified as new observations and evidence is found. Example: Kingdoms used to be the highest classification, but scientists added Domains when more organisms were discovered. We know that the Earth is flat and nothing will change that.

EXAMPLES OF WHEN SCIENTIFIC KNOWLEDGE CHANGED: Evidence supports that the Earth is a sphere, not flat. Cells come from pre-existing cells, not spontaneous generation. The continents are in constant motion through plate tectonics, instead of fixed landforms.

WE DO COLLABORATIVE ACTIVITY:

REVISITING THE BELLRINGER In recent scientific history, the classification of protists has changed several times. They now have been regrouped to consider their development over time instead of simply by how they move or look. Which statement best describes such changes in scientific knowledge? a) An entire species must be discovered before a classification system can be made. b) Early ideas about taxonomy should be unchallenged so that scientists can continue to classify new species. c) Modern technology and processes make it possible to prove an idea so further research is not necessary. d) As more knowledge is gained about organisms and natural events, scientific interpretations change as necessary. *

YOU DO TIME!

YOU DO QUESTION #1 Until the 1500s, doctors thought diseases were caused spontaneously. Scientists began proposing that diseases were caused by seedlike entities that could be passed among people. After the invention of the microscope, doctors came to know that many diseases were actually caused by microscopic living organisms, like bacteria. What does this suggest about the nature of scientific knowledge? a) Scientific knowledge should not be considered valid because it changes over time. b) Technology has improved enough that scientific knowledge can stop changing. c) New discoveries and evidence are more important than repeatable results. d) Scientific knowledge changes over time based on evidence.

YOU DO QUESTION #2 Gregor Mendel conducted research about genetics by breeding pea plants. Although he could not actually see into cells, he deduced from his results that each of an organism s traits is determined by two factors (alleles). Long after Mendel s work, microscopes were improved and scientists observed that chromosomes in the nucleus occurred in matching pairs. It is now accepted that the two alleles for each trait are located on homologous chromosomes. What does this demonstrate about science? a) Advances in science may result from new interpretations of previous work. b) Improvements in equipment and data gathering can disprove previous conclusions. c) Earlier scientists did not have the proper equipment and materials to make their conclusions. d) Much of early scientific research was faulty because the earlier scientists did not practice the same data-gathering practices as modern scientists.

YOU DO QUESTION #3 During the nineteenth century, biologists knew that South America and Africa contained similar fossils. These fossils let them to believe that a temporary land bridge between South America and Africa allowed ancient species to move between both continents. In the twentieth century, evidence showed that South America and Africa were once part of the same larger continent and that there were no land bridges between them. How should biologists respond to the new geological finding? a) Biologists should reject the geological finding, because it is new. b) Biologists should ask physicists what to do, because physics is a more exact science. c) Biologists should reject the belief in ancient species, because there were no land bridges. d) Biologists should update the history of life, because it should include the new geological finding.