Chapter 1

Phylogenetic Diagram of Living Organisms

Section 2 Themes in Biology

Section 2 Themes in BiologyChapter 1

Diversity and Unity of Life, continued

• Three Domains of Life– The three domains of life are Bacteria, Archaea,

and Eukarya.– The six kingdoms include Archaea, Bacteria,

Protista, Fungi, Plantae, and Animalia.

Section 3 The Study of BiologyChapter 1

Objectives• Outline the main steps in the scientific method.

• Summarize how observations are used to form hypotheses.

• List the elements of a controlled experiment.

• Describe how scientists use data to draw conclusions.

• Compare a scientific hypothesis and a scientific theory.

• State how communication in science helps prevent dishonesty and bias.

Section 3 The Study of BiologyChapter 1

Scientific Processes

Section 3 The Study of BiologyChapter 1

Observing and Asking Questions

• The process of science begins with an observation.

• An observation is the act of perceiving a natural occurrence that causes someone to pose a question.

• Observation: Flies were observed around the carcasses at the butcher shops.

• Question: Where do the flies at the butcher shop really come from? Does rotting meat turn into or produce the flies?

Section 3 The Study of BiologyChapter 1

Forming a Hypothesis

• A hypothesis is a proposed explanation for the way a particular aspect of the natural world functions.

Hypothesis:Rotten meat does not turn into flies. Only flies can make

more flies.

Section 3 The Study of BiologyChapter 1

Forming a Hypothesis, continued

• Predicting– To test a hypothesis, scientists make a prediction

that logically follows from the hypothesis.

• Prediction: If meat cannot turn into flies, rotting meat in a sealed (fly-proof) container should not produce flies or maggots.

Section 3 The Study of BiologyChapter 1

Designing an Experiment

• Performing the Experiment– A controlled experiment compares an

experimental group and a control group and only has one variable.

Section 3 The Study of BiologyChapter 1

Designing an Experiment, continued

• Performing the Experiment– The control group provides a normal standard

against which the biologist can compare results of the experimental group.

– The experimental group is identical to the control group except for one factor.

Section 3 The Study of BiologyChapter 1

Designing an Experiment, continued

• Performing the Experiment– The experimenter manipulates the independent

variable.– The experimenter measures the dependent

variable because it is is affected by the independent variable.

Section 3 The Study of BiologyChapter 1

Designing an Experiment, continued

• Testing the Experiment– Experiments should be conducted without bias

and they should be repeated.

Testing: Wide-mouth jars each containing a piece of meat were subjected to several variations of “openness” while all other variables were kept the same. control group — These jars of meat were set out without lids so the meat would be exposed to whatever it might be in the butcher shop.experimental group(s) — One group of jars were sealed with lids, and another group of jars had gauze placed over them.replication — Several jars were included in each group.

Section 3 The Study of BiologyChapter 1

Collecting and Analyzing Data

• Analyzing and Comparing Data– Scientists analyze data to draw conclusions about

the experiment performed.

• Data: Presence or absence of flies and maggots seen in each jar was recorded. In the control group of jars, flies were seen entering the jars. Later, maggots, then more flies were seen on the meat. In the gauze-covered jars, no flies were seen in the jars, but were observed around and on the gauze, and later a few maggots were seen on the meat. In the sealed jars, no maggots or flies were ever seen on the meat.

Section 3 The Study of BiologyChapter 1

Drawing Conclusions

• Making Inferences– An inference is a conclusion made on the basis of

facts and previous knowledge rather than on direct observations.

Conclusion(s): Only flies can make more flies. In the uncovered jars, flies entered and laid eggs on the meat. Maggots hatched from these eggs and grew into more adult flies. Adult flies laid eggs on the gauze on the gauze-covered jars. These eggs or the maggots from them dropped through the gauze onto the meat. In the sealed jars, no flies, maggots, nor eggs could enter, thus none were seen in those jars. Maggots arose only where flies were able to lay eggs. This experiment disproved the idea of spontaneous generation for larger organisms.

Section 3 The Study of BiologyChapter 1

Drawing Conclusions, continued

• Applying Results and Building Models– Scientists often apply their findings about the

natural world to solve practical problems.

Section 3 The Study of BiologyChapter 1

Constructing a Theory

• A theory is a set of related hypotheses confirmed to be true many times, and it can explain a great amount of data.

Section 3 The Study of BiologyChapter 1

Communicating Ideas

• Publishing a Paper– Scientists submit research papers to scientific

journals for publication.– In peer review, the editors of a journal will send

submitted papers out to experts in the field who anonymously read and critique the paper.

Section 3 The Study of BiologyChapter 1

Honesty and Bias

• Communication between scientists about their methods and results helps prevent dishonesty and bias in science.

Section 3 The Study of BiologyChapter 1

Honesty and Bias

• Conflict of Interest– The threat of a potential scandal based on

misleading data or conclusions is a powerful force in science that helps keep scientists honest and fair.