Download Laboratory 6: Video - "What Darwin Never Saw"

Laboratory 6.
Video: “What Darwin Never Saw”
from “The New Explorers” - Kurtis Productions
This video documentary describes how a husband and wife team of scientists studying in the Galapagos
Islands are using finches to study evolution. There are 13 species of finches on the islands and the scientists
are studying two species of finch located on an isolated island. They describe the variation among the
finches and how environmental influences and natural selection events can affect the population of finches.
As you watch this video look for relationships between environmental influences, competition, natural
selection and evolution.
Points to think about and questions to answer as you watch the video:
1.
In the first few minutes of the film, the narrator, Bill Kurtis uses two phrases which are technically
incorrect in their biological content:
a) He said “the finches held the secret to the origin of life.” He should have said “the finches
held the secret to the origin of _____________.
b) He said “but it was only a theory.” He should have said “but it was
__________________________.
2.
What did the Grants do when they went ashore on the island to be sure nothing was brought onto
the island from the “outside world” (no insects or other creatures which might disrupt the natural
habitat on this isolated island)? Why?
3.
What is the main enemy of the finches on Daphne Major Island? __________________
4.
What is the finch on Daphne which digs into cactus blossoms? __________ finch.
5.
What major biological process have the Grants seen TWICE during their 22 years of studying the
islands?
6.
In what year did the Grants first come to the island?____________
7.
The three questions they were trying to answer by studying the finches were:
a) Do species compete?
b) Why are some populations so variable?
c) ___________________________________________________
8.
Why was Daphne Island chosen?
_________________________________________________________
9.
One species of finch was G. scandens (Cactus finch). The other species was G. fortis. What is its
common name?
10. How many finches did they find and band on the island?
11. Your choice: some interesting facts given about Darwin in his experiences on the HMS Beagle –
tortoises, etc.
12. What did the Grants find when it didn’t rain for 18
months?__________________________________________________________
13. They found that natural selection operates under _______________conditions.
14. Birds with ________________beaks tended to survive the drought baest. Why?
15. All but about _________% of all species which have ever existed are extinct now- so what per
cent are extinct?_________________
16. The Grants measured the beaks of the next generation birds (from those which survived the
drought). What was the size of those beaks (compared to the average size previously)
___________________
17. What surprising conclusion did this observation provide good evidence for?
18. Which finches survived best after it rained so heavily (for 8 months)? _____________________
Why?_________________________________
Even though evolution is called a “theory” there is so much evidence in favor of evolution of species that
most scientists consider that evolution is a fact. Scientists may still disagree on precisely how evolution
occurs- whether gradually, or intermittently in huge changes precipitated by climatic or environmental
change. The events in this film describe two climatic changes (first the drought – then the heavy rain) that
resulted in two natural selection events. These events occurred over a relatively short period of time- much
shorter than Darwin had envisioned. During the period studied the Grants did not see an “evolution” of the
finches but observed natural selection events which over many years may lead to evolution of the species.
Since there are 13 species of Finches on the islands it is presumed that these all evolved from one original
species and that competition and natural selection are responsible for the evolution of the 13 different
species of Finches on the Galapagos Islands.
The Scientific Method
Science is a way of knowing the natural world that involves testing hypotheses or explanations. The
scientific method can be applied to the unusual and the commonplace. You use the scientific method when
you investigate why your once white undershirt is now pink. Your hypothesis might be that when you wash
a red sweatshirt with white undershirts the undershirts turn pink. This hypothesis can be tested through
observation and experimentation.
Hypothesis: an idea or supposition that provides the basis for further investigation and testing – the
hypothesis is an idea to be tested and either confirmed or refuted by experimental data. The investigator
should be “neutral” to the results of the experiment – i.e. he/she presents this idea to be tested but has no
bias as to whether the idea is confirmed or refuted by the data. In science there is seldom a single test that
will provide results that clearly support or disprove a hypothesis.
Experimentation: A test or trial to determine something not yet known. The experiment should be
designed to “test” the hypothesis. An experiment should be carefully designed to determine whether a
“hypothesis” is confirmed or refuted. A poorly designed experiment may yield ambiguous results and will
not answer whether the hypothesis is correct or incorrect. If a hypothesis is shown by experiment to be
incorrect then the scientist then poses a new hypothesis that will subsequently be tested by experiment. An
experiment can disprove the hypothesis but can never prove it, because there is always the possibility of
discovering additional information.
Control: A baseline for comparison in an experiment. For example, if the investigator wishes to
determine the effect of a drug on mice – some mice must not receive the drug, but they would receive the
substance in which the drug was dissolved. This provides a basis to determine the effect of the drug alone.
A “control” is used to ensure that the results obtained in an experiment are true and not due to some
“artifact” or poor design in the experiment.
Controlled experiments are not the only way to test a hypothesis. The test of a hypothesis may include
experimentation, additional observations, or the synthesis of information from a variety of sources.
Considering existing knowledge is important in the scientific inquiry. Watson and Crick won the Nobel
Prize for their development of a 3-D model of the structure of DNA. They did not perform a controlled
experiment in the laboratory but tested their powerful hypothesis through the use of existing evidence from
other research. Some areas of science require comparative observations and the accumulation of data from
a variety of sources.
Replication: Scientific investigations are not valid if the conclusions drawn from them are based on one
experiment with one or two individuals. Generally, the same procedure or observation needs to be repeated
several times, providing consistent results.
Once data is collected, it must be organized and summarized so that the scientists can determine if the
hypothesis has been supported or refuted. Many times the data is compiled into tables or graphs in order to
help analyze and interpret the results and to enhance the clarity of the work.
Theory: A theory is stronger than a hypothesis. It is a statement of apparent relationships about observed
phenomena for which there are multiple verifications. If the data collected supports a hypothesis, it is
subject to still more predictions and tests. If this additional data continues to support the hypothesis,
confidence in its correctness increases, and the hypothesis comes to be considered a theory. In the case of
natural selection it is considered a theory because many researchers from many of the biological fields have
continued to validate the theory with their observations and experimentations.
After watching the video documentary “What Darwin Never Saw”
1.
Describe possible hypotheses studied by the Grants.
2.
Did their observations support or refute their hypothesis?
3.
What were some of the ways they collected data?
4.
How was this data standardized year to year?
5.
Describe possible ways to display the data.
6.
Did their observations add to the “theory of natural selection”?