chapter 1 how do biologists study life?ocw.nctu.edu.tw › course › biology ›...

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Copyright 2005—Brooks/Cole—Thomson Learning

Tobin and Dusheck: Asking About Life, 3E Chapter 1

Chapter 1

How Do BiologistsStudy Life?



Biology is the study of life

Biologists ask questions about all aspectsof living organisms· Bios logos means “a discourse on life”in

Greek

Biology has many sub-disciplines· from biochemistry, molecular biology to

environmental study

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Biology is the study of life

Why study Biology?

To understand the ecosystem on earth and theliving organisms in this system

To stop and prevent the wrong doing due toignorance

To recover the damaged environment

To preserve our ecosystem

To make life enjoyable



Problems on Our Earth

Run out of non-renewable resources(coal, oil, gas) green energy ??

Lands are filled with wastes ??

Renewable (replaceable) resources aredamaged ???

Environment changed ??? Worse!

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How to study Biology?

Study of biology involves:•Observation•Asking questions•Having hypothesis•Accumulating facts•Analyzing dataproblems solved?•Learning about new topics



Key Questions•How do biologists come up with

questions and then answer them?•How do biologists use statistics to

plan and evaluate experiments?•How are all organisms alike?•Why are all the members of a species

alike?•How do organisms become different?

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Thinking About the Possibilities

•Analyze Barry Marshall’sexperiment on himself. What stepsof the scientific method did hefollow? Which steps were notfollowed?



•Dr. BarryMarshalldemonstratedthat bacterium(Helicobacterpylori) but notstomach acidcausing ulcer.

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Testable Hypothesis

•Scientific method only works ontestable hypotheses

•Testable if experiments coulddisprove it, if it were incorrect

•If testable, hypothesis will makepredictions that can be tested byexperiment



Theory

•Group of related hypotheses thathave withstood rigorousexperimental testing

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Scientific Method•The scientific method is the way

scientists approach a question:•Focus on a single answerable

question — reductionism•Observation, either with our senses

or instruments•Create a hypothesis or model — a

guess of how things work that alsomakes predictions•Test the hypothesis, are predictions

right?



Experiments•Procedure carried out under

controlled conditions–Controls: a version of the

experiment that is the same exceptfor the variable being tested —minus drug, for example–Replicates, because each organism

is unique; Then compare averageswith statistics

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Results

•Results of scientific tests maysupport a hypothesis, but cannotprove it

•Results may disprove a hypothesis•May require redesign of

experiment



Statistics

•Used to evaluate results•Measures probability that what

we see is not a random effect•Measures a sample, not an

entire population

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Sampling•Because we cannot use an entire

population, we must use a smallnumber that represent the entirepopulation — a random sample

•Non-random samples may skew theresults; sample size can also skewresults

•Statistics can be used to determine if2 populations are different, based onthe variation in data — standarddeviation



Sampling a Population

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What is Life?



What is Life?

Life can be viewed as a flow a energythat is channeled by organisms in theorganized, orderly, small, manageablesteps to do the work of living.

Origin of life on earth?

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Themes of life

What distinguishes living from nonliving?

•Certain characteristics define life.•Living organisms possess all of these

characteristics.•Non-living, however, have one or a few,

but not all of these characteristics.



Thinking About the Possibilities

•What features of living things doviruses have?

•Are they lacking any features ofliving things?

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Thinking About the Possibilities•Which of the following is alive and why?–A neutered dog or cat cannot reproduce.–A gasoline-powered chain saw takes in

energy, metabolizes the fuel, respondsto stimuli (it will start if you pull thecord). They even change with time, theirteeth getting duller and their paintchipping.–Some adult insects never eat. They just

lay eggs and die. Since they are notobtaining energy from theirsurroundings, are they alive?



Characteristicsof Living

Organisms

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Living Organisms•What is life? Living things have these

things in common:–Are organized–Are made of cells–Perform chemical reactions–Obtain energy–Respond to environment–Change over time–Reproduce–Have common evolutionary history



Living organisms are made ofcells

The Cell Theory•The cell is the basic unit of living things•All cells come from preexisting cells•Living things exhibit hierarchical

organization from cells to ecosystems inthe biosphere

Cell Tissue Organ Organ System

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Cell Types•Basic building blocks of organisms•200’s of kinds of cells just in humans•2 basic types:–Prokaryotic, no nuclei or other

membrane organelles; bacteria–Eukaryotic, have nuclei and other

organelles; plants, animals, fungi,protozoans



Cellular and hierarchical organization

•Living things, or organisms, are eithermulticellular (composed of many cells) orunicellular (composed of a single cell).

•Single-celled organisms that work togetheras a team as celled colonial organisms(like the Volvox).

•Cells in multicellular organisms areorganized to form the structures andperform the functions of the organisms.

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Hierarchical organization of Cell

•Tissues are groups of similar cells thatwork together to perform the function.

•Organ is a structural and functional unitforned by various tissues.

•An organ system is a group of organs thatfunction together to carry out the principleactivities of the organism.

Cell Tissue Organ Organ System



Characteristics of Life:Transformation of energy

Autotrophs are producers•most obtain energy from sunlight and

transform it through photosynthesis

Heterotrophs are consumers•obtain energy by ingestion of

producers or other consumers

Metabolism Requires Energy

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Characteristics of Life:Interaction with one another

Interactions occur at all levels of organizationInteraction within organisms

Cells -->Organs -->Organ SystemsOrgan Systems -->Organisms Interaction between organisms and

environmentOrganisms -->Populations -->Communities -

->Ecosystems -->Biosphere



Interaction with environmentPopulation consists of the individuals of a

given species that occur together at oneplace and at one time.

Community of organisms is made up ofpopulations of different species.

Ecosystem is a community of plants,animals, and microorganisms.

Biosphere: In this environment livingsinteract with each other and with nonlivingresources in variuos ways.

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Characteristics of Life:Emergent properties

The whole is more than the sum of itsparts

1 + 1 > 2 ??

Only 1% difference between genomes ofhuman and chimpanzee.

Human ≠ Chimpanzee



Reproduction

All living things have biologicalinformation that directs their structure andfunction, and ultimately, their emergentproperties.•DNA (deoxyribonucleic acid) is the hereditary

material.•Genes are DNA sequences coding for

functional proteins.•Genome is the sum of all the DNA

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Reproduction

Living things reproduce and passbiological information to their offspring

Reproduction may be sexual or asexual•Sexual: offspring arise from two

parents•Asexual: offspring arise from one

parent (bacteria, certain plants,animals, protists, and fungi)



Regulation•Organisms must create barriers

between the outside world and theorganism — skin, cell membrane

•Resist change — maintainhomeostasis–Detecting change–Counteracting change

•Animals regulate temperature, thirst,hunger, sperm production

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Classification of Organisms•Three domains:–Archaea–Eubacteria–Eukarya, has 4 kingdoms•Plantae•Animalia•Fungi•Protista



The Kingdoms of Life

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Eubacteria•Bacteria that live

and grow incommonenvironments —our gut and skin,fresh and saltwater, and almostevery otherenvironment onEarth



Archaea

•Bacteria that livein extremeenvironments —hot springs, saltponds

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Plantae

•Multicellularplants, frommosses toredwood trees

•Have cellulosecell walls,performphotosynthesis



Animalia

•Multicellularanimals

•Sponges,worms,insects, birds,fish, mammals

•Have no cellwalls; obtainenergy fromother organisms

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Fungi

•Multicellular,with cell wallscontainingchitin; obtainfood byabsorption

•Mushrooms,yeast



Protista

•Single celledeukaryotes; livemostly in water

•Amoebas, algae,water molds,slime mold

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Diversity

•There are about 1.4 million namedspecies, but there may be as manyas 100 million living species; this isonly about 1% of the species thathave ever lived — most are extinct

•This diversity has arisen byevolution; we are all related and aredescended from a common ancestor



Genetics

•Genes determine the structures,appearance, and to some extent,the behavior of an organism

•Genes are inherited by offspringfrom their parents

•Genes are made of DNA; DNA isused to make proteins, theworking parts of a cell

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Adaptations

•Members of a species shareadaptations — structures andbehaviors that make them fit for aparticular environment

•Adaptations are inherited; those thatpromote survival and reproduction willbe inherited more often by the nextgeneration

•Diversity comes from different types ofadaptations to different environments



Evidence for Evolution

•Fossils arepreservedremnants oforganisms;some are verydifferent fromany organismsalive today

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Natural Selection

•Charles Darwinsuggested amechanism forevolution:NaturalSelection; hisreasoning camefrom agriculture



Key Concepts

•Testable hypotheses bothanswer questions and suggestentirely new questions•A good experiment includes 1 or

more controls and a largeenough sample to compensatefor variation in the data

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Key Concepts

•All living things reproduce,evolve, respond to theirenvironment, and consist of asingle cell or orderedarrangements of many cells•All organisms on Earth have

descended from a commonancestor through a processcalled evolution

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