Homework 1 Bio 1309
Why did Alvarez's team choose to use iridium instead of beryllium-10 to determine how long it took to form the clay layer?
Beryllium-10 decays too quickly to be used to date rocks that are 65 million years old.
A series of steps designed to help you solve problems and answer questions while reducing the influence of personal preconceived ideas
scientific method
All of the following are potential "culprits" that might have played a role in triggering the KT mass extinction except
heavy metal poisoning
In science, an educated guess is called a/an
hypothesis
In an experiment, the one variable that is changed is called the
independent variable
What skill is a scientist using when she listens to the sounds that whales make?
making observations
The process of obtaining information by using the senses is called a/an
observation
When the scientific community started paying attention to Alvarez's asteroid hypothesis, all of the following lines of evidence were explored except
reversal of magnetic fields
What is the correct order of steps in the scientific method? (1) Analyze the results (2) Ask a question (3) Communicate results (4) Draw conclusions (5) Make a hypothesis (6) Test the hypothesis
2, 5, 6, 1, 4, 3 Ask a question Make a hypothesis Test the hypothesis Analyze the results Draw a conclusion Communicate results
What was the supernova hypothesis?
A supernova caused the mass extinction at the KT boundary.
After rejecting the supernova hypothesis, what became the new hypothesis for the Alvarez team?
An asteroid impact caused the mass extinction at the KT boundary.
What did Alvarez notice about the marine fossils found in different rock layers marking the 65 million years old boundary between the Cretaceous and Tertiary periods?
Correct The lower layer was sedimentary rock with abundant marine fossils. The middle layer was a thin clay layer with no fossils. The upper layer was sedimentary rock with very few marine fossils.
What were the two possible hypotheses about how long it took to form the clay layer?
Few years versus few thousand years
What evidence found in the KT boundary by Alvarez's team supported the supernova hypothesis?
High levels of iridium
Alvarez's team had two hypotheses about the amount of time it took to form the clay layer. What did they expect to see for each hypothesis?
If it took a few years to form the clay layer, there would be no detectable iridium. If it took a few thousand years, there would be small detectable amounts of iridium.
Why did Alvarez and his team reject the supernova hypothesis?
No plutonium-244 was found in the KT boundary.
How could the impact of a large asteroid on Earth cause the dinosaurs to become extinct?
The asteroid impact caused tons of dust to float into earth's atmosphere, blocking out the sun. This slowed down photosynthesis and disrupted food webs. The lack of adequate sunlight and food killed many plants, leading to the death of the dinosaurs.
What is the "iridium anomaly"?
The clay layer at the KT boundary contains extremely high levels of iridium.
Which of the following statements best describes the data in the graph below?
The more sugar people eat, the more likely they are to get cavities.
What did Alvarez's team actually find when they measured the iridium in the clay layer?
They found very high levels of iridium
Which of the following statements accurately describes the Alvarez's team conclusions after they measured the iridium levels in the clay layer?
They rejected both hypotheses.
What became Alvarez's new research question after the iridium anomaly was discovered?
Why are the iridium levels so high at the KT boundary?
An experiment that tests only one factor at a time by using a comparison of a control group and an experimental group is?
a controlled experiment
In an experiment, the factor that we measure is called the
dependent variable
A scientist conducted an experiment to determine how the amount of salt in a body of water affects the number of plants that can live in the water. In this experiment, the independent variable is
the amount of salt in the water
A scientist hypothesizes that the temperature at which an alligator's egg is incubated will determine whether the alligator offspring will be male or female. The dependent variable is
the gender of the alligator offspring
A scientist conducted an experiment to determine how the amount of salt in a body of water affects the number of plants that can live in the water. In this experiment, the dependent variable is
the number of plants in the water
A scientist hypothesizes that the temperature at which an alligator's egg is incubated will determine whether the alligator offspring will be male or female. The independent variable is
the temperature
When you decide whether or not the data supports the original hypothesis,
you are drawing a conclusion
