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Introduction to Biology

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Why a Study of Biology is Important?

Societal•Medicine

•Public Health

• Worldwide Water Crisis

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Why a Study of Biology is Important?

Philosophical•Evolution

•Genetics

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.1-

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Why a Study of Biology is Important?

Personal• To be informed

• Support your cause

• Make it your life work

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[bahy-ol-uh-jee]

Bio = life

...ology = the study of

Biology is the science that studies life

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The Scientific Method in Action

A systematic way of gaining information

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The Scientific Method: Observation

An observation is a thoughtful and careful recognition of an event or a fact.

The careful observation of a phenomenon leads to a question.– How does this happen?– What causes it to occur?

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The Scientific Method:The Hypothesis

Hypothesizing – question an observation– propose possible solutions to questions based on what

is already understood about the phenomenon Hypotheses must:

– be logical– account for all current information– make the least possible assumptions– be testable

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Testing Hypotheses

Hypotheses need to be tested to see if they are supported or disproved.– Disproved hypotheses are rejected– Hypotheses can be supported but not proven

Ways to test a hypothesis:– Gathering relevant historical information

Retrospective Studies

– Make additional observations from the natural world– Experimentation

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The Scientific Method: Experimentation

Experiments– rigorous tests to determine if the solutions are supported

Experiments attempt to recreation an occurrence– tests whether or not the hypothesis can be supported or

rejected

There are many types of experiments– laboratory, clinical trials, surveys, statistical analyses

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Experimental Design

All experiments have key elements in common:

– Experiments must be controlled this means that all aspects except for one variable must be kept

constant usually include any two groups.

– Experimental group: variable is altered, independent variable – Control group: variable is not altered, dependent variable

– Experiments use models to recreate occurrences, but in a controlled setting

model organisms, ISS, cohorts

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Experimental Design

Experiments must:– use large numbers of subjects and/or must be

repeated several times (replication)– be independently reproducible

The validity of experimental results must: – be tested statistically

chi-squared test for statistical significance

– be scrutinized by other scientists peer reviewed

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Theory

If the hypothesis is supported by ample experimental data, it leads to a theory.

A theory may be defined as a widely accepted, plausible general statement about a fundamental concept in science.

– The germ theory states that infectious diseases are caused by microorganisms.

Many diseases are not caused by microorganisms, so we must be careful not to generalize theories too broadly.

– Theories continue to be tested Exceptions identified Modifications made

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A Scientific Law

A scientific law is a uniform and constant fact of nature that describes what happens in nature.

– An example: All living things come from pre-existing living things.

Scientific laws promote the process of generalization.– Inductive reasoning– Since every bird that has been studied lays eggs, we can generalize

that all birds lay eggs.

Once a theory becomes established, it can be used to predict specific facts.

– Deductive reasoning– We can predict that a newly discovered bird species will lay eggs.

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Scientific Communication

Data is shared with the scientific community through research articles published in scientific journals.

– peer review

Scientists present preliminary data at conferences.

Scientists collaborate directly by phone and e-mail.

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A Sample Experiment

Scientific American August 2010

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A Sample Experiment

Article: Hardt, Marah J. and Safina, Carl. “Threatening Ocean Life from the Inside Out.” Scientific American August 2010: Vol. 303 2.

What types of observations were being made? State a hypothesis that was tested. Describe an experiment that was conducted. Discuss a variable that was studied and describe how constants

where maintained in the experiment. How was a model system was used to simulate the conditions being

studied. How were the complex processes being studied reduced to their

simplest parts? What was learned from the experiments?

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The Science of BiologyChapter 1

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1.1 The Science of Life

• Biology unifies much of natural life

• Biology attempts to define life

• Biology Living reveals a hierarchical organization of living systems

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Properties of Life

• Living organisms:– are composed of cells (Cellular Organization)– are complex and ordered (Ordered Complexity)– respond to their environment (Sensitivity)– can Grow, Develop and Reproduce– obtain and use energy (Energy Utilization)– maintain internal balance (Homeostasis) – allow for Evolutionary Adaptation

•The definitions of life are adapting with the field- where do viruses fit in?

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Levels of Organization1. Cellular Level

• Atoms molecules organelles cells

2. Organismal Level• Tissues organs organ systems

3.Population Level• Population species biological community

4. Ecosystem Level• Biological community + physical habitat (soil, water,

atmosphere)

5. The Biosphere• The entire planet thought of as an ecosystem

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Levels of Organization

Cellular Organization cells

organellesmolecules

atoms

The cell is the basic unit of life.

Fig. 1.1-1

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Levels of Organization

Organismal Level

organism

organ systems

organs

tissues

Fig. 1.1-2

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Levels of Organization

Population Level

ecosystem

community

species

population

Fig. 1.1-3

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Levels of Organization

• Each level of organization builds on the level below it but often demonstrates new features

• Emergent properties: new properties present at one level that are not seen in the previous level

• New properties emerging may be greater than the sum of the the parts

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1.2 The Nature of Science

• Science aims to understand the natural world through observation and reasoning

• Science begins with observations, therefore, much of science is purely descriptive

• Science uses both deductive and inductive reasoning

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The Nature of Science

• Deductive reasoning uses general principles to make specific predictions.

• Inductive reasoning uses specific observations to develop general conclusions.

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The Nature of Science

• Scientists use a systematic approach to gain understanding of the natural world:

• Observation• Hypothesis formation• Prediction• Experimentation• Conclusion

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The Nature of Science

• A hypothesis is a possible explanation for an observation.

• A hypothesis:• must be tested to determine its validity

• is often tested in many different ways

• allows for predictions to be made

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The Nature of Science

• The experiment:• tests the hypothesis

• must be carefully designed to test only one variable at a time

• consists of a test experiment and a control experiment

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The Nature of Science

• If the hypothesis is valid, the scientist can predict the result of the experiment

• Conducting the experiment to determine if it yields the predicted result is one way to test the validity of the experiment

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Think Like a Scientist

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The Nature of Science

• Scientists may use:• reductionism - to break a complex process down to its simpler parts

• models – to simulate phenomena that are difficult to study directly

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Test the early hypothesis of Spontaneous Generation

Fig. 1.4

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The Nature of Science

A scientific theory:• is a body of interconnected concepts

• is supported by much experimental evidence and scientific reasoning

• expresses ideas of which we are most certain

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1.3 An Example of Scientific Inquiry: Darwin and Evolution

• Charles Darwin served as naturalist on mapping expedition around coastal South America.

• Used many observations to develop his ideas

• Proposed that evolution occurs by natural selection

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Voyage of the Beagle

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Charles Darwin

• Evolution: Modification of a species over generations

• “descent with modification”

• Natural Selection: Individuals with superior physical or behavioral characteristics are more likely to survive and reproduce than those without such characteristics

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Darwin’s Evidence

• Similarity of related species• Darwin noticed variations in related species living in different locations

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Unnatural Selection

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Darwin’s Evidence

Thomas Malthus:

Population growth vs. availability of resources

-population growth

is geometric

-increase in food

supply is arithmetic

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Darwin’s Evidence

Population growth vs. availability of resources

• Darwin realized that not all members of a population survive and reproduce

• Deduced that the organisms best adapted to obtaining resources would survive to reproduce

• Darwin based these ideas on the writings of Thomas Malthus

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Post-Darwin Evolution Evidence

Fossil record– Intermediate Organisms

Mechanisms of heredity- Early criticism of Darwin’s ideas were resolved by Mendel’s theories for genetic inheritance

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Post-Darwin Evolution Evidence

Comparative anatomy

- Homologous structures have same evolutionary origin, but different structure and function.

- Analogous structures have similar structure and function, but different evolutionary origin.

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Homologous Structures

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Post-Darwin Evolution Evidence

Molecular Evidence

- Our increased understanding of DNA and protein structures has led to the development of more accurate phylogenetic trees.

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1.4 Unifying Themes in Biology

Cell theory• The cell theory describes the organization of

living systems

• All living organisms are made of cells, and all living cells come from preexisting cells

Fig. 1.11a

Single Celled Organisms

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Fig. 1.11b

Multi-Cellular Organisms

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1.4 Unifying Themes in Biology

Molecular basis of inheritance• The molecular basis of inheritance explains

the continuity of life

• DNA encodes genes which control living organisms and are passed from one generation to the next

• The DNA code is similar for all organisms (The Central Dogma)

Fig. 1.12

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Unifying Themes in Biology

Structure and Function• The proper function of a molecule is

dependent on its structure

• The structure of a molecule can often tell us about its function

• Four major classes of Biomolecules1. Nucleic Acids

2. Amino Acids

3. Lipids

4. Carbohydrates

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Unifying Themes in BiologyEvolutionary Change• The diversity of life arises by evolutionary

change leading to the present biodiversity we see

• Biology attempts to classify life’s great diversity based on these unifying themes

• Currently all living things are classified into 3 Domains subdivided into Kingdoms (more on taxonomy to come)

• This process is always changing

Fig. 1.13

The Diversity of Life

Three Domains:1. Eukarya2. Archaea 3. Bacteria

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Fig. 1.13-1

Domain Eukarya is Divided into four Kingdoms:1. Plantae2. Fungi3. Animalia4. Protista

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Fig. 1.13-2

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Fig. 1.13-3

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Unifying Themes in Biology

Evolutionary Conservation• Evolutionary conservation explains the unity

of living systems

• The underlying unity of biochemistry and genetics argues that all life has evolved from the same origin event

• Critical characteristics of early organisms are conserved and passed on to future generations

Fig. 1.14

Homeodomains

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Unifying Themes in Biology

Cells are information-processing systems

• Every cell in an organism carries the same genetic information

• The control of gene expression allows cells to differentiate into different cell and tissue types

• Cells also process information received from the environment and respond to maintain homeostasis

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Unifying Themes in Biology

Emergent properties• New properties are present at one level of

organization that are not seen in the previous level

• The whole is greater than the sum of its parts

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The Science of BiologyEnd Chapter 1