EQ: HOW IS BIOLOGY STUDIED AS A SCIENCE? THE NATURE OF SCIENCE Jacqueline Irizarry, Eboni Harris, Nick Karpiw

SCANNING ELECTRON MICROSCOPE (SEM) This microscope scans the surface of a specimen with a beam of electrons ~ Shows a three-dimensional image of the specimens surface. ~Uses electrons instead of lights to form an image. The specimens are coated with a very thin layer of a metal that deflects the electrons. Not used to look at living things

SCANNING ELECTRON MICROSCOPE *Scanning Electron Microscopes have a magnification range of ,000x

COMPOUND LIGHT MICROSCOPE This microscope transmits visible light through several lenses to produce a enlarged image of a sample. Best for looking at single cell layers, and cells and tissues. ~ Has low resolution compared to electron microscopes. Mostly used for getting an overview of a sample.

COMPOUND LIGHT MICROSCOPE * School Compound Light Microscopes have a magnification range of x

TRANSMISSION ELECTRON MICROSCOPE (TEM) TEM allows you to look at very thin cross sections of an sample such as a cell. ~ Produces a 2-D image Its very good for looking at the relationships between structures at very high resolution and the internal structure. Can not be used to look at living things. Able to show much higher resolution when looking at objects.

TRANSMISSION ELECTRON MICROSCOPE * TEM can achieve close to 50,000,000x magnification

DISSECTING MICROSCOPE Dissecting microscopes have low magnification and provides a 3-D image of the specimen. It has more space that allows you to view larger specimens. Used to observe the details of of the surface structures of bigger specimen.

DISSECTING MICROSCOPE * Has a lower magnification of 15-30x

THEORIES A scientific theory is a well-substantiated explanation of some aspect of the natural world that is acquired through the scientific method and repeatedly tested and confirmed through observation and experimentation to always be true.

LAWS A scientific law is a statement based on repeated experimental observations that describes some aspects of the universe it applies under the same conditions, and implies that there is a causal relationship involving its elements however is not a law.

HYPOTHESIS a supposition or proposed explanation made on the basis of limited evidence as a starting point for further investigation and has yet to be proven.

VARIABLES Independent Variable (test variable) - a variable (often denoted by x ) whose variation does not depend on that of another. Dependent variable (out-come variable) - a variable (often denoted by y ) whose value depends on that of another. Side notes: in an experiment the dependent variable will always depend on the independent variable hence the name.

WHAT DO YOU KNOW? 1.While speaking to a colleague, a scientist makes the following statement: "I propose that Bald Eagle eggs in northern Maine will have thinner shells than those from birds in southern Alaska due to increased levels of pesticides in the water." This statement is a A) theory B) law C) conclusion D) hypothesis

WHAT DO YOU KNOW? 2. Which statement below correctly identifies the difference between laws and theories? A) Laws describe phenomena, while theories explain why phenomena exist. B) Laws are a statement of fact, while theories are a statement of opinion. C) Laws explain why phenomena exist, while theories explain how. D) Laws are a prediction of phenomena, while theories are an explanation.

WHAT DO YOU KNOW 3. Why do scientists develop a hypothesis before conducting research? A) It gives them direction on how to interpret the results of their research. B) It helps to predict outcomes and define the parameters of the research. C) Hypotheses give the researcher an outcome to shape their work around. D) Hypotheses help a researcher decide which observations to record and which to ignore.

ANSWERS 1.D 2.A 3.B