concepts in bio-1

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Concepts & Methods in

Biology

Every sentence I utter must be understoodnot as an affirmation, but as a question.

Niels Henrik David Bohr (1885-1962)Danish physicist.

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Biology

Scientific study of life

Lays the foundationfor asking basic questions about life

and the natural world

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Molecules of Life

All things are madeup of the same unitsof matter

Living things aremade up of a certainsubset of molecules:

Nucleic acids

Proteins

Carbohydrates

Lipids

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DNA (deoxyribonucleic acid)

Signature molecule of life

Molecule of inheritance

Directs assembly ofamino acids

DNA model,

corresponding to

that ofWatson

and Crick

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DNA and Inheritance

Inheritance

Acquisition of traits by way of

transmission ofDNA from parent tooffspring

Reproduction

Mechanism by which an organismproduces offspring

Governed by instructions in DNA

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DNA Guides

Development

Multicelled organisms develop

Series of stages

Instructions for each stage in DNA

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Nothing Lives without EnergyEnergy = Capacity to do work

Metabolism = Reactions by whichcells acquire and use energy togrow, survive, and reproduce

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Sensing and Responding

Organisms sense changes in their

environment and make responses tothem

Receptors detect specific forms of

energy (stimuli)

Allows maintenance of homeostasis

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Levels of Organization

Cell

Multicelled Organism

Population

CommunityEcosystem

Biosphere

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cytoplasm

nucleus

plasmamembrane

The Cell

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A multi-celled organism

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Population

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Community

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Ecosystem

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The Biosphere

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Interdependencies among

OrganismsProducers

Make their own food

ConsumersDepend on energy stored in

tissues of producers

DecomposersBreak down remains and wastes

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Producers

Consumers,

Decomposers

NUTRIENT

CYCLING

ONE-WAY FLOW

OF ENERGY

In time, all energy

flows back to the

environment.

ENERGY FROM

SUN

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Unity of Life

All organisms:

Are composed of the same

substancesEngage in metabolism

Sense and respond to the

environmentHave the capacity to reproduce

based on instructions in DNA

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Diversity of Life

Millions of living species

Millions more now extinct

Classification schemes attempt

to organize diversity

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Scientific Names

Devised by Carolus Linnaeus

First name is genus (plural, genera)

Homo sapiens genus is Homo

Second name is species within genus

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Eubacteria

(Bacteria)

Archaebacteria

(Archaea)

Eukaryota

(Eukaryotes)

3D

omains

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Origin of life

EubacteriaArchaebacteria

Eukaryotes

Protistans Plants Fungi Animals

6Kingdoms

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Single cells

No nucleus ororganelles

Smaller, less

complex

Prokaryotic

Organisms

Eukaryotic

Organisms

Single- or multi-

celled Nucleus and other

organelles

Larger, morecomplex

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Mutation & Adaptive Trait

A source of variation where there is achange in structure ofDNA

Basis for the variation in heritabletraits

Most are harmful

Adaptive trait a trait that gives theindividual an advantage in survival orreproduction, under a given set ofcircumstances

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Artificial Selection

Breeders are selective agents

Individuals exhibiting favored traits

are bred

Favored traits become more common

in population

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Natural Selection Individuals vary in some heritable traits

Some forms of heritable traits are more

adaptive

Natural selection is differences in

survival and reproduction among

individuals that vary in their traits

Adaptive forms of traits become more

common than other forms

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Antibiotic Resistance

Antibiotics are used to kill bacteria

Mutations for antibiotic resistance

exist or arise Antibiotic-resistant bacteria survive

and reproduce better than

nonresistant

Over time, proportion of antibiotic-

resistant bacteria increases

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The Scientific Method Observe phenomenon

Develop hypotheses

Make predictions

Devise test of predictions

Carry out test and analyze results

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Inductive Logic

Using observations and facts to arrive

at generalizations or hypotheses

Observation: Eagles, swallows, and

robins have feathers

Hypothesis: All birds have feathers

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Deductive Logic

Drawing a specific conclusion based

on a generalization

Generalization Birds havefeathers

Example Eagles are birds

Conclusion Eagles have feathers

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Role of Experiments Used to study a phenomenon under

known conditions

Allows you to predict what will

happen if a hypothesis is not wrong

Can never prove a hypothesis 100%

correct

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Report on experimental design, test results,

and conclusions drawn from results

Draw samples from some aspect of nature

CONTROL GROUP

The variable being

tested is absent

EXPERIMENTAL GROUP

The variable being

tested is present

Compare and analyze the test results

Compile results Compile results

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Scientific Theory A hypothesis that has been tested for

its predictive power many times and

has not yet been found incorrect

Has wide-ranging explanatory power

E.g. Darwins theory of evolution bynatural selection

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Biological Therapy

Experiments

Problem: Can we use viruses thatattack bacteria (bacteriophages) to

fight infections?

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Sample Experiment Hypothesis Bacteriophages can

protect mice against infectious

bacteria

Prediction Mice injected with

bacteriophages will not die as a result

of bacterial injection

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Experiment Test Experimental group

Inject with bacteria andbacteriophage

Control group

Inject with bacteria and salinesolution (placebo)

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Experiment Results & Conclusion

Experimental group:

All mice lived

Control group:

All mice died

Conclusion Bacteriophageinjections protect mice against

bacterial infections

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Minimizing Variables

All mice were same age and sex,

reared under same conditions

Each mouse in each test group

received exact same treatment

All mice in control group received

same amount of saline

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Can the Scientific Method

provide answers to allquestions?

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Limits of Science Scientific approach cannot provide

answers to subjective questions

Cannot provide moral, aesthetic, or

philosophical standards

Conflict with supernatural beliefs

Copernicus

Darwin

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Scientists Raise Questions

The external world, not internalconviction, must be the testing

ground for scientific beliefs