http://education.nationalgeographic.com/education/activity/observations-and-hypotheses/?ar_a=1
Students will:
- differentiate between an observation and a hypothesis and apply that understanding to new information
- explain that scientists constantly challenge hypotheses, which can force them to make more observations and collect more data, helping them to reject some hypotheses and further strengthen others
www.education.nationalgeographic.com/
Date
Name ____________________________________________________________
Read the National Geographic news article online from April, 2009, “Giant Pterosaurs Couldn’t Fly,
http://news.nationalgeographic.com/news/2009/04/090428-giant-pterosaurs-fly.html
Study Suggests.” Use the definitions below and information from the article to determine observations
and hypotheses about giant pterosaurs. For questions 1 and 2, answer questions below each
of the quotes from the article.
observation noun data collected by using senses, such as sight, or an instrument, such as a
ruler or thermometer.
hypothesis noun a possible explanation for a set of data. A requirement of a hypothesis is that
it is testable using the scientific method.
scientific method noun a method of research in which a question is asked, data are gathered,
a hypothesis is made, and the hypothesis is tested.
1. Animals heavier than 90 pounds (41 kilograms) with wingspans greater than 16.7 feet (5.1 meters)
would not be able to flap fast enough to stay aloft…in an environment similar to the present.
a. What parts of this statement are based on observations?
b. What is the proposed explanation, or hypothesis?
2. Giant pterosaurs, colossal winged reptiles that lived alongside the dinosaurs, have long been
considered the heaviest animals ever to [fly].
a. What parts of this statement are based on observations?
b. What is the proposed explanation, or hypothesis?
3. Is it possible that the statements above both include hypotheses, even though they provide two
completely different explanations based on the same pterosaur fossil? Explain.
_
4. Describe the observations Researcher Sato made before arriving at his hypothesis.
5. Which of these responses to Sato’s hypothesis are observations, and which are hypotheses?
Label each.
___________________ a. …Sato’s findings don’t really apply to pterosaurs or even to all birds.
___________________ b. Argentavis, a giant bird, had a wingspan of 20 feet (6 meters).
___________________ c. Argentavis… seems to have been able to fly.
___________________ d. …giant pterosaur fossils all seem to have extraordinarily thin bone walls.
___________________ e. …giant pterosaurs might have been lighter than their size would suggest.
6. Explain your decision about whether statement (e.) above is an observation or hypothesis. How
did you make that decision?
7. How do you think the following hypothesis by Sato might be tested?
But if pterosaurs really were capable of sustained flight, ‘we must think about the possibility of
drastic change in other environmental factors, such as much lighter gravity or much denser air
over geological time.’
8. The American Association for the Advancement of Science states that “hypotheses are valuable,
even if they turn out not to be true, if they lead to fruitful investigations.” How might this apply to
our understanding of pterosaurs?
Pterosaurs: Observations And Hypotheses
© 2011 National Geographic Society
Giant Pterosaurs Couldn't Fly, Study Suggests
Giant pterosaurs, colossal winged reptiles that lived alongside the dinosaurs, have long been considered the heaviest animals ever to take to the skies.
But new research suggests that the notion of giant pterosaurs soaring over Earth simply doesn't fly.
Based on the weights and body sizes of modern birds, a new study finds that animals heavier than 90 pounds (41 kilograms) with wingspans greater than 16.7 feet (5.1 meters) wouldn't be able to flap fast enough to stay aloft.
The conclusion casts serious doubt on the flying ability of large pterosaurs such as Quetzalcoatlus, thought to be one of the largest airborne animals of all time.
The late-Cretaceous creature may have weighed up to 551 pounds (250 kilograms) and had up to a 34.1-foot (10.4-meter) wingspan—nearly as wide as a schoolbus is long.
"I think that the giant pterosaurs could not stay aloft in an environment similar to the present," said study leader Katsufumi Sato, an associate professor at the University of Tokyo's Ocean Research Institute.
Even if they could stay up, the bulky beasts would have had trouble getting off the ground in the first place, Sato said.
"Takeoff is the hardest task. I suppose they could not take off using only muscular efforts."
Setting Limits
Sato, who is also a National Geographic Society emerging explorer, journeyed to the southern Indian Ocean to study the world's largest bird, the wandering albatross, and four smaller bird species. (The National Geographic Society owns National Geographic News.)
All five species are considered to be soaring birds—flyers that use a strategy of gliding punctuated by sporadic flapping, as pterosaurs are generally thought to have flown.
Comparing the data across species, Sato found that the flapping speeds required for a bird to take off and then stay cruising are linked to its body size.
Sato's findings, appearing tomorrow in the journal PLoS ONE, also suggest that, in theory, a soaring flyer can weigh no more than 90 pounds (41 kilograms) with a wingspan no wider than 16.7 feet (5.1 meters).
Swimming Pterosaurs?
Other scientists are not quite convinced that Sato's research means large pterosaurs couldn't get airborne.
"One possibility is that Sato's findings don't really apply to pterosaurs or even to all birds," suggested Davin Unwin, a paleobiologist at the University of Leicester in the U.K.
For example, Argentavis, a giant bird thought to have existed six million years ago, had a wingspan of 20 feet (6 meters) and seems to have been able to fly, Unwin said.
What's more, Unwin said, giant pterosaur fossils all seem to have extraordinarily thin bone walls, which could mean the animals were lighter than their size would suggest.
Makoto Manabe, a senior scientist at the National Museum of Nature and Science in Tokyo, also thinks it's possible that pterosaurs were simply lighter than we currently think.
Or, if pterosaurs couldn't fly, Manabe wonders whether they might have been swimmers, "using their wings as fins like penguins."
"Having said that," he added, "their wings do not look very efficient at swimming."
According to study leader Sato, it's possible heavy pterosaurs overcame their difficulties during takeoff by launching themselves from high places such as trees or cliffs.
But if pterosaurs really were capable of sustained flight, "we must think about the possibility of drastic change in other environmental factors, such as much lighter gravity or much denser air over geological time," he said.
Biggest Critic
In general, Sato thinks the reactions from paleontologists have been "not so negative," despite the fact that his conclusions would bring huge pterosaurs abruptly down to Earth.
He is expecting his biggest critic to be much closer to home.
"My six-year-old son, Takuto, is a dinosaur freak," he said, "and will never agree with my findings."
