Invitation to Biology

Chapter 1

Biology

Scientific study of life

Lays the foundation for asking basic questions about life

and the natural world

What Am I Doing Here?

• To learn how organisms are constructed, how they function, where they live, and what they do

• To help develop, modify, and refine ideas about life

Biology is a way of thinking critically about lifeBiology is a way of thinking critically about life Biology can help us to better understand human impact Biology can help us to better understand human impact

on nature, such as an oil field burning out of control on nature, such as an oil field burning out of control during the Persian Gulf Warduring the Persian Gulf War

Impacts, Issues: Impacts, Issues: What Am I Doing Here? What Am I Doing Here?

Fig. 1.1, p.2

Life’s Underlying Unity

• Life’s organization extends from the molecular level to the biosphere

• Shared features at the molecular level are the basis of life’s unity

Life’s levels of organization

Levels of Organization

Molecules of Life

• Atoms are the basic units of matter

• Living things are made up of a certain subset of molecules:– Nucleic acids– Proteins– Carbohydrates– Lipids

Nothing Lives without Energy

Energy = capacity to do work

Metabolism = processes by which cells acquire and use energy for

maintenance, growth, and reproduction

Energy Flow

• Usually starts with energy from the

sun

• Transfers from one organism to

another

• Flows in one direction

• Eventually is lost as heat

Interdependencies among Organisms

ProducersMake their own food

ConsumersObtain energy by eating other organisms

DecomposersBreak down remains and wastes

Energy input, from sun

NutrientCycling

Producersplants, and other

self-feeding organisms

Consumersanimals, most fungi,

many protists, many bacteria

Energy output (mainly metabolic heat)Fig. 1-3, p.5

Unity of Life

All organisms

– Consist of one or more cells

– Have the capacity to reproduce based on instructions in DNA

– Engage in metabolism

– Sense and respond to the environment

Homeostasis

• Organisms maintain certain conditions in their internal environment

• A defining feature of life

Life’s Diversity

• Millions of living species

• Millions more now extinct

• Each species has someunique traits

Classification Systems

• Organisms are grouped into three domains:

Eubacteria(Bacteria)

Archaebacteria(Archaea)

Eukaryotes(Eukarya)

Life’s diversity

• Single celled

• No nucleus

• Smaller, less complex

• Archaebacteria, eubacteria

Prokaryotes Eukaryotes

• Single- or multicelled

• Nucleus

• Larger, more complex

• Fungi, protistans, plants, animals

Bacteria

• The most common prokaryotes

Archaea

• Prokaryotes

Mutation: Source of Variation

• Mutation = change in structure of DNA

• Basis for variation in heritable traits

• May be harmful, neutral, or beneficial

Evolution

• Heritable change in a line of descent over time

• Changes in populations result in diversity

Scientific Method

• Observe phenomenon

• Develop hypotheses

• Make predictions

• Devise test of predictions

• Carry out test and analyze results

Role of Experiments

• Study a phenomenon under known conditions

• Tests the prediction of the hypothesis

• Can never prove a hypothesis 100% correct

Experimental Design

• Control group – A standard for comparison– Identical to experimental group except for

variable being studied• Experimental group

– Includes one variable being studied

Scientific Theory

• An explanation of the causes of a wide range of related phenomena

• Is consistent with all collected data

• Used to make predictions

• Still can be disproved

Experiments with Synthetic Fat

Question: Does Olestra®, a synthetic fat replacement made from sugar and oil,

cause intestinal cramps?

p.10

Designing an Experiment: Olestra ®

Results 93 of 529 people get cramps later (17.6%)

89 of 563 people get cramps later (15.8%)

Experiment Control GroupEats regularpotato chips

Experimental GroupEats Olestrapotato chips

Fig. 1-8, p.10

HypothesisOlestra® causes intestinal cramps.

PredictionPeople who eat potato chips made with Olestra will be more likely to get intestinal cramps than those who eat potato chips made without Olestra

Conclusion

Percentages are about equal. People who eat potato chips made with Olestra are just as likely to get intestinal cramps as those who eat potato chips made without Olestra.These results do not support the hypothesis. Stepped Art

Designing an Experiment: Olestra ®

Limits of Science

• Scientific method – cannot provide answers to subjective

questions– cannot provide moral, aesthetic, or

philosophical standards– may conflict with supernatural beliefs

Limits of Science

The external world, not internal

conviction, is the testing ground for

scientific theories

Table 1-1, p.13