Biology 112 Chapter 1 Overview (Accompanies GR Chap1) Holyoke Walsh

Biology 112Chapter 1 Overview

(Accompanies GR Chap1)Holyoke Walsh

Copyright Pearson Prentice Hall

The goal of science is to:• investigate and understand the

natural world.• explain events in the natural world.• use those explanations to make

useful predictions.


1-2 How Scientists Work

Scientists make educated guesses about how things work the way they do. These are called HYPOTHESIS.

How do scientists test hypotheses?

A hypothesis should be tested by an experiment in which only one variable is changed at a time.

Scientific Method Summary

1) Ask questions, make observations2) Gather information 3) Form a hypothesis (educated guess)4) Set up a controlled experiment • Manipulated variable - the variable

that is deliberately changed (aka independent variable)Responding variable is variable that is observed (aka dependent variable)

5)Record and analyze results 6)Draw a conclusion7)Repeat & share findings


Asking a QuestionMany years ago, people wanted to know how living things came into existence. They asked:

•How do organisms come into being?

Aristotle

• 2300 y.a people thought that some “special force” brought some things into being from nonliving material

Ex:

• Beetles just “appeared” on cow dung

• Mice were “found” on grain

• Maggots “showed up” on meat


Forming a HypothesisOne early hypothesis was spontaneous generation aka: abiogenesis.

For example, most people thought that maggots spontaneously appeared on meat.

In 1668, Redi proposed a different hypothesis: that maggots came from eggs that flies laid on meat.


Redi’s Experiment

Controlled Variables:jars, type of meat,Location, temperature,time

Covered jarsUncovered jars

What do you think are the manipulated and responding variables in this experiment??


Redi’s Experiment

Manipulated Variable:Gauze covering that keeps flies away from meat

Responding Variable:whether maggots appear Maggots appear.

Severaldays pass.

No maggots appear.

John Needham – mid 1700’s

• English Scientist who tried to attack Redi’s work. He had a flask with a sealed cork and it had no microorganisms growing in it.

• Next, he heated it for a short time and corked the flask and microorganisms appeared.

• He believed that the little “animalcules” must have come from the gravy!


Repeating Investigations

Spallanzani's Test of Redi's Findings

Gravy is boiled. Gravy is boiled.

Which variables are controlled??


Repeating InvestigationsSpallanzani's Test of Redi's Findings

Flask is open. Flask is sealed.

•Is the flask the manipulated or responding variable??

Copyright Pearson Prentice HallH

Repeating InvestigationsSpallanzani's Test of Redi's Findings

Gravy is teemingwith microorganisms.

Gravy is free ofmicroorganisms.

Helped prove the theory of BIOGENESIS!!!! Living things come from other living things!


Pasteur's Test of Spontaneous Generation–Louis Pasteur conclusively disproved the

hypothesis of spontaneous generation.–Pasteur showed that all living things come

from other living things.


Pasteur’s Experiment

Broth is boiledBroth is freeof microorganismsfor a year.

Curved neck isremoved.

Broth is teeming with microorganisms.


The Impact of Pasteur’s Work

•He began to uncover the nature of infectious diseases, showing that they were the result of microorganisms.•Pasteurization of dairy products


1-3 Studying Life


What are some characteristics of living things?


Living things share the following characteristics:*REFERENCE PAGE – pages 16/17 of student text!!

1. made up of units called cells – smallest unit of life considered to be “alive”

Characteristics of Living Things

2. Reproduction


3. Universal genetic code• Genetic code is common, with minor variations, to

every organism on Earth.

That information, carried in DNA, is copied and passed from parents to offspring


4. Grow & Develop


5. obtain and use materials and energy


6. respond to their environment


7. Maintain a stable internal environment (called homeostasis)


8. change over time

• Make a table with the heading “CAR”

Living NonLiving

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Biology 112 Chapter 1 Overview (Accompanies GR Chap1) Holyoke Walsh