Do Now 4/30:DO NOT record today’s Do Now – answer on notes

Several students are conducting an experiment to test the effect of exercise on heart rate. Students do 20 sit-ups in one minute of

exercise. The data chart below shows the heart rate at one-minute intervals for each student.

Which of these is the dependent variable?

A. timeB. heart rateC. type of exerciseD. number of sit-ups

Dependent Variable = B. heart rate• In any experiment, the dependent variable is

the measured outcome or result.

• The independent variable is the variable whose effect is being investigated.

• What is the independent variable here?

• Minutes of exercise

Theories

• In science, theory has a very different meaning than in common parlance

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Theory Scientific theories are supported by many different tested hypotheses and observations.

A theory describes a broad set of related observations

Theory of Evolution by Natural Selection

• The basic idea of the theory of evolution is that the organisms alive today are the descendents of older organisms.

• It proposes that new species come about when populations of older species change over long periods of time.

• It is based on the idea of natural selection: organisms which survive and reproduce the most have more offspring and pass their traits on to the next generation more than less successful ones

Example: The deadliest lion has the most offspring…

There’s A Dragon in My Garage

• Read the excerpt from The Demon-Haunted World by Carl Sagan.

• As you read, consider the question:

what makes something scientific?

What Makes an Explanation of a Phenomenon “Scientific?”

• Limited to the observable / measureable• Testable / falsifiable

The picture above shows the Maryland state fossil, a shell of an ancient species

Ecphora quadricostata. What kind of organism do you think it was, and why?

Fossil Formation

• Fossilization is a rare process that occurs under specific conditions (swamps are good for example)

• They are found in SEDIMENTARY rock, which is deposited layers of soil and organic material smushed together.

archaeopteryx

Tiktaalik

Australopithicus:Lucy

Hypothesis we’re testing• Hypothesis: The organisms that have inhabited

Earth in the past are similar to the ones here now.

• Prediction: If the organisms that have inhabited Earth in the past

are similar to the ones here now, then…we should be able to figure out what type of organisms made fossils that we’ve found.

Fossil Exploration• There are 9 different fossils at different locations

around the room. You will spend about 2-3 minutes examining each one.

• While at each station, carefully observe the specimen, and make a quick sketch of the fossil organisms. It doesn’t have to be beautiful, just good enough to know which one it is

• After completing your sketches, finish the chart on your handout. For each fossil, write down what organisms alive today you think are most similar to the fossil.

The big idea

• The organisms found on Earth today are the descendents of organisms that lived long ago.

Homework

• On syllabus