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The Study of Life

Table of Contents

Section 1 Introduction to Biology

Section 2 The Nature of Science

Section 3 Methods of Science

Chapter 1



Characteristics of Living Organisms

Biology is the study of life.

All living organisms share certain general properties that separate

them from nonliving things.

Properties of Life

» Cellular organization

» Reproduction

» Metabolism

» Homeostasis

» Heredity

» Responsiveness

» Growth and development

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Characteristics of Living Organisms, continued

• Cellular organization - every living thing is composed of one or more cells

• Reproduction - all living things are able to reproduce

• Metabolism - all obtain and use energy to run the processes of life

• Homeostasis - living organisms maintain a consistent internal environment

• Heredity - living things pass traits to offspring

• Responsiveness - all living things respond and adjust to the environment

• Growth and development - all living things grow and develop

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Biology

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Unifying Themes of Biology

As you study biology you will repeatedly encounter the following

seven themes.

1. Cellular Structure and Function

2. Reproduction

3. Metabolism

4. Homeostasis

5. Heredity

6. Evolution

7. Interdependence

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Unifying Themes of Biology, continued

1. Cellular Structure and Function • Cells are highly organized, tiny structures with thin

coverings called membranes. All living things are made of one or more cells. A cell is the smallest unit capable of all life functions.

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2. Reproduction • Reproduction is the process by which organisms

make more of their own kind from one generation to the next.

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3. Metabolism • Metabolism is the sum of all the chemical reactions

carried out in an organism. Almost all energy used by living organisms is originally captured from sunlight.

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4. Homeostasis • Homeostasis is the maintenance of a stable internal

conditions in spite of changes in the external environment. An organism unable to balance its internal conditions with its environmental conditions could become ill and die.

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5. Heredity • Heredity is the passing of traits from parent to

offspring. The basic unit of heredity is called a gene. Genes are coded in a molecule called deoxyribonucleic acid (DNA). Genes determine an organism’s traits. A change in the DNA of a gene is called a mutation. Most mutations are harmful, but some mutations can help an organism survive.

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6. Evolution • Evolution is defined as change in the inherited

characteristics of species over generations. A species is a group of genetically similar organisms that can produce fertile offspring. Natural selection is the process in which organisms with favorable traits are more likely to survive and reproduce.

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Evolution

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7. Interdependence • The organisms in a biological community live and

interact with other organisms. Ecology is the branch of biology that studies the interactions of organisms with one another and with the nonliving part of their environment. Organisms are dependent on each other and on their environment.

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Unifying Themes of Biology

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Observation: The Basis of Scientific Research

Observation is the act of noting or perceiving objects or

events using the senses.

• All scientists have a certain way of investigating the

world.

• Scientific investigations begin with observations.

• Observations cause scientists to ask questions about

their observations.

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Stages of Scientific Investigations

Scientific investigations tend to have common stages.

• These stages are called the Scientific Method.

• There is more than one way to conduct an

investigation.

• Scientific Methods or Scientific Processes are

more accurate terms for the stages of scientific

investigation.

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Stages of Scientific Investigations, continued

Scientific Processes include the following stages.

• Collecting observations

• Asking questions

• Forming hypotheses and making predictions

• Confirming predictions (with experiments when

needed)

• Drawing conclusions

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Scientific Processes

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• Hypothesis—an explanation that might be true, a

statement that can be tested by additional

observations or experimentation

• Prediction—the expected outcome of a test,

assuming the hypothesis is correct.

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• Experiment—a planned procedure to test a

hypothesis.

• Control group—a group in an experiment that

receives no experimental treatment. The control

group is necessary for comparing the results of the

experiment.

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• Independent variable—the factor that is changed in

an experiment.

• Dependent variable—the variable that is measured

in an experiment, the outcome of the dependent

variable depends on what is done to the independent

variable.

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Drawing Conclusions

Once data are collected

and analyzed, a conclusion

is made as to whether the

data support the

hypothesis.

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Viewing Conclusions in Context

• There is often more than one possible reason for a

result.

• All of the factors that may affect an outcome must be

considered.

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Scientific Explanations

Constructing a Theory

Theory a set of related hypotheses that have been

tested and confirmed many times by many scientists.

• A theory unites and explains a broad range of

observations.

• The word theory is used by the general public to

mean a guess, or lack of certainty.

• In science, a theory is a well-supported scientific

explanation that makes useful predictions.

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Scientific Explanations, continued

Constructing a Theory

Scientists report their results.

• Scientific reports are reviewed by other scientists.

• Scientific reports allow other scientists to use the

information obtained in an experiment.

• Scientific reports also allow other scientists to repeat

and test experiments.

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