Concepts

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Concepts Methods in Biology

• Chapter 1

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Biology

• Scientific study of life
• Lays the foundation for asking basic questions
  about life and the natural world

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Why Study Biology?

• 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

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Molecules of Life

• All things are made up of the same units of
  matter
• Living things are made up of a certain subset of
  molecules
• Nucleic acids
• Proteins
• Carbohydrates
• Lipids

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DNA (deoxyribonucleic acid)

• Signature molecule of life
• Molecule of inheritance
• Directs assembly of amino acids

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DNA and Inheritance

• Inheritance
• Acquisition of traits by way of transmission of
  DNA from parent to offspring
• Reproduction
• Mechanism by which an organism produces 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 Energy

• Energy Capacity to do work
• Metabolism Reactions by which cells acquire
  and use energy to grow, survive, and reproduce

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Sensing and Responding

• Organisms sense changes in their environment and
  make responses to them
• Receptors detect specific forms of energy
  (stimuli)
• Allows maintenance of homeostasis

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Levels of Organization

• Cell
• Multicelled Organism
• Population
• Community
• Ecosystem
• Biosphere

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Interdependencies among Organisms

• Producers
• Make their own food
• Consumers
• Depend on energy stored in tissues of
  producers
• Decomposers
• Break down remains and wastes

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Energy Flow

• Usually starts with energy from sun
• Transfer from one organism to another
• Energy flows in one direction
• Eventually, all energy flows back to the
  environment

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ENERGY FROM SUN
Producers
NUTRIENT CYCLING
Consumers, Decomposers
ONE-WAY FLOW OF ENERGY
In time, all energy flows back to the environment.
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Unity of Life

• All organisms
• Are composed of the same substances
• Engage in metabolism
• Sense and respond to the environment
• Have 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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3 Domains
Eubacteria (Bacteria)
Archaebacteria (Archaea)
Eukaryota (Eukaryotes)
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6 Kingdoms
Protistans
Plants
Fungi
Animals
Eukaryotes
Archaebacteria
Eubacteria
Origin of life
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Prokaryotic Organisms
Eukaryotic Organisms

• Single cells
• No nucleus or organelles
• Smaller, less complex

• Single- or multi-celled
• Nucleus and other organelles
• Larger, more complex

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Mutation Source of Variation

• Mutation change in structure of DNA
• Basis for the variation in heritable traits
• Most are harmful

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Adaptive Trait

• A trait that gives the individual an advantage in
  survival or reproduction, under a given set of
  circumstances

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Evolution

• Genetically based change in a line of descent
  over time
• Population changes, not individuals

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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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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 have feathers
• 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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Experimental Design

• Control group
• A standard for comparison
• Identical to experimental group except for
  variable being studied
• Sampling error
• Nonrepresentative sample skews results
• Minimize by using large samples

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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
• Darwins theory of evolution by natural selection

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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 internal conviction,
  must be the testing ground for scientific beliefs