Biology in the 21st Century

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Biology in the 21st Century

• Unit 1

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What is Science?

• How is science different from other human
  endeavors?
• Deals only with the natural world
• Scientists collect and organize information in an
  orderly way in search of patterns connections
  between events
• Scientists propose explanations that can be
  tested by examining evidence
• What is the goal of science? To investigate and
  understand nature, to explain events in nature,
  and to use those explanations to make useful
  predictions.

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The Scientific Process Observation

• The first step in the scientific process is
  making observations
• Involves using one or more of the senses to
  gather information
• The information gathered is called evidence, or
  data
• It is important when making observations to be
  objective and avoid bias
• Observations can be classified into 2 types
• Quantitative (involves numbers measuring)
• Qualitative (involves characteristics not easily
  measured or counted)

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The Scientific Process Question or Inference

• Observations are usually followed with questions
  or inferences.
• Question who, what, why, where, when, how
  regarding phenomena observed
• Inference a logical interpretation based on
  prior knowledge and experience

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The Scientific Process Hypothesis

• A hypothesis is a possible general explanation
  for a set of observations or an answer to a
  scientific question
• In science, a hypothesis is useful only if it can
  be tested
• Hypotheses must be falsifiable
• Hypotheses may arise from prior knowledge,
  logical inferences, or educated guesses
• Hypotheses are tested via controlled experiments

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The Scientific Process Predictions

• Following a general hypothesis, a specific
  prediction is usually made.
• Like hypotheses, predictions must also be
  testable and falsifiable
• Example Hypothesize that there is a difference
  in the age of the trees between the north side of
  the hill and the south side of the hill.
  Specifically predict that the trees on the north
  side are older.

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The Scientific Process Experiment

• Scientists usually test hypotheses and
  predictions with unbiased, controlled experiments
• Controlled experiments test ONLY ONE variable at
  a time
• The experiment may support or refute the
  hypothesis
• No matter the outcome, a tested hypothesis has
  value in science because it helps researchers
  advance scientific knowledge

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The Scientific Process Concept Map
OBSERVATION
QUESTION
HYPOTHESIS PREDICTION
EXPERIMENT
DATA SUPPORT HYPOTHESIS
DATA REFUTE HYPOTHESIS
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How Scientists Work Setting Up a Controlled
Experiment

• Whenever possible, a hypothesis should be tested
  by an experiment in which only one variable is
  changed at a time.
• All other variables should be kept unchanged, or
  controlled
• This type of experiment is called a controlled
  experiment
• Manipulated variable (independent)
• Responding variable (dependent)
• A control group should always be specified this
  is the group to which you will compare your
  experimental group

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How Scientists Work Drawing a Conclusion

• Scientists use the data from an experiment to
  evaluate the hypothesis and draw a solid
  conclusion
• They use evidence to determine whether or not a
  hypothesis was supported or refuted

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How a Theory Develops

• As evidence from numerous investigations builds
  up, a particular hypothesis may become so well
  supported that scientists consider it a theory
• In science, the word theory applies to a
  well-tested explanation that unifies a broad
  range of observations in the natural world

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Scientific Laws Theories

• Scientific laws describe what nature does under
  certain conditions, and will predict what will
  happen as long as those conditions are met
• Often mathematically defined
• Scientific theories explain how nature works
• Are generally non-mathematical

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Scientific Laws Theories

• Commonalities between a scientific law and
  theory
• BOTH are based on tested hypotheses
• BOTH are supported by a large body of empirical
  data
• BOTH help unify a particular field
• BOTH are widely accepted by the vast majority of
  scientists within a discipline
• BOTH could be shown wrong at some time if there
  are data to suggest so

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Studying Life

• The word biology means the study of life
• A biologist is a scientist who uses a scientific
  method to study the living world

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Characteristics of Living Things

• Living things share several characteristics
• Made up of units called cells
• Reproduce
• Based on a universal genetic code
• Grow and develop
• Obtain and use materials and energy
• Respond to their environment
• Maintain a stable internal environment
• Change over time

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Reproduction

• All organisms produce new organisms through a
  process called reproduction
• Sexual two cells from different parents unite to
  produce the first cell of the new organism
• Asexual the new organism has a single parent

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Based on a Genetic Code

• With minor exceptions, the DNA genetic code
  determines the inherited traits of every organism
  on Earth.
• Deoxyribonucleic acid
• With asexual reproduction, offspring and their
  parents have the same traits
• With sexual reproduction, offspring differ from
  their parents in some ways

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Growth and Development

• Every type of organism has a distinctive life
  cycle a particular pattern of growth and change
  occurring over the organisms lifetime
• Growth (increase in size)
• Development (cells in an organism not only
  increase in number but also become different)

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Need for Materials Energy

• Organisms use energy and a constant supply of
  materials to grow, develop, and reproduce
• Materials energy are also needed just for an
  organism to stay alive
• Metabolism is the combination of chemical
  reactions through which an organism builds up or
  breaks down materials as it carries out its life
  processes

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Response to the Environment

• Organisms live in constantly changing
  environments
• Amount of light and temperature can vary from day
  to day
• Nearby living and nonliving things can change
• Organisms can make changes to their environment
• Each organism responds to environmental changes
  in its own way
• Examples
• Plants tend to grow in a direction toward a
  source of light (phototropism).
• Birds fly south for the winter.

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Maintaining Internal Balance

• The process by which organisms keep their
  internal conditions relatively stable is called
  homeostasis
• This condition is constantly being threatened by
  changes in the environment
• If homeostasis is disrupted in a major way, an
  organism cannot survive

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Evolution

• As a group, any given kind of organism can
  evolve, or change over time
• Changes are not generally significant over a few
  generations, but over thousands or millions of
  years, changes can be dramatic
• The ability of a group of organisms to change
  over time is invaluable for survival in a world
  that is always changing

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Levels of Biological Organization