The Study of Life

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The Study of Life

• Chapter 1

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What is Life?

• The concept of living can be difficult to
  define, since many qualities of living things can
  be seen in non-living things
• Crystals (non-living) can grow.
• A thermostat (non-living) responds to the
  environment.

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Qualities of Living Things

• Living things
• are complex, organized, and made up of cells.
• maintain homeostasis.
• respond to stimuli.
• reproduce and grow.
• use materials and energy.
• as species, adapt and evolve.

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Complex and organized
All living things have DNA, which contains
information to build cell parts.
Cells are the basic unit of living things.
Organisms can be single-celled, or cells can
organize into tissues and organs.
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Maintain Homeostasis
Living organisms need to maintain an internal
environment, such as maintaining temperature.
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Respond to stimuli
All living things have ways of sensing the
environment that allow them to respond to threats
and find food or favorable environments.
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Reproduce and grow
Living things produce more of their kind through
reproduction. The young grow to maturity and the
cycle begins again.
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Use materials and energy
In order to maintain complexity, maintain
homeostasis, to grow, and to respond to the
environment, organisms must take in energy and
materials. Living things have a metabolism and
give off waste products as they use materials.
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Still a relevant question
What is life? isnt just a question that you
left behind in Kindergarten.
Astrobiologists who search for signs of life on
other planets look for many of the same
characteristics of terrestrial life.
Microbiologists studying nanobacteria may
challenge our current understanding of life.
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Scientific Inquiry

• Science is an investigation of the natural world,
  using evidence from nature to support
  explanations.
• The methods used by scientists to investigate the
  natural world are called Scientific Inquiry.
• Scientific Laws and Theories are products of
  scientific inquiry.

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Hypothesis Testing

• Scientific Inquiry is often used to test
  hypotheses.
• A hypothesis is a tentative explanation for an
  observation.
• A valid hypothesis must be specific, testable,
  and falsifiable.

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Scientific Evidence

• Based on natural causes.
• Uniform in time and space.
• Perceived similarly by many people.
• Objective, measurable.

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Forming Hypotheses

• Scientific Inquiry is often used to test
  hypotheses.
• A hypothesis is a tentative explanation for an
  observation.
• A valid hypothesis must be specific, testable,
  and falsifiable.

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Specific

• A hypothesis is specific if it addresses
  particular observations and has specific
  variables.
• Not specific Toxins in water make fish
  populations decline.
• Specific The herbicide glyphosate causes trout
  embryos to die in the egg when present in water
  at levels of 100 parts per million or more.

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Falsifiable

• A hypothesis is falsifiable if it can be true or
  false, either supported or rejected by evidence.
  Note we do not say proven or disproven.
• Not falsifiable Black licorice is the best kind
  of licorice. (Opinions cannot be true or false.)
• Falsifiable Over half of WOU students in our
  biology class prefer black licorice over red.

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Testable

• A hypothesis is testable if involves specific
  variables in the real, physical world that can be
  measured directly or indirectly.
• Not testable Students do poorly on exams
  because of bad luck.
• Testable Biology students who make outlines and
  concept maps while studying their textbook score
  10 better on exams than students who only read
  the textbook.

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A hypothesis does not

• have to be true at the start of the
  experiment. We dont know until the experiment is
  over whether the hypothesis is supported or not.
• have to explain everything. It only has to
  address one variable at a time. If you try to
  write a hypothesis that explains everything, it
  is no longer specific.

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Hypotheses often begin with an observation that
leads to questions.
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Questions invite possible explanations.
These possible explanations are hypotheses. To be
valid, a hypothesis must be specific, testable,
and falsifiable but it doesnt have to be
correct! In fact, you dont know if it is correct
or not until you test it.
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Each possible explanation hypothesis can give
rise to a prediction, often stated in an
IF...THEN format.
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A good prediction suggests a procedure that can
test the hypothesis.
Scientists test hypotheses and accept or reject
hypotheses based on data. They do not set out to
prove hypotheses or they may bias their results.
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Once the procedures are carried out, scientists
use the data to reach a conclusion regarding the
hypothesis.
Notice that the hypothesis is supported rather
than proven.
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Experiments are one type of scientific inquiry.
Experiments test variables to try to find the
cause of natural events.
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Observational studies are also part of scientific
inquiry. Much of Astronomy and Paleontology, for
example, involves observational science.
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Laws and Theories

• In general
• Scientific Laws and Theories are both products of
  Scientific Inquiry.
• Laws tend to be descriptions of natural phenomena
  in given circumstances.
• Theories tend to be explanations of how natural
  phenomena work.

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Law of Gravity describes what happens when you
drop a rock or launch a rocket at the moon.
Gravitational Theory explains why dropped objects
fall toward the center of the mass of the Earth.
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Mendels Laws of Heredity Describe patterns of
inheritance in terms of probability.
Darwins Theory of Natural Selection Explains
why inherited traits change in populations over
generations.
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Recap

• Living things are complex, organized, and
  maintain homeostasis.
• Scientists study living things using scientific
  inquiry to make observations and test hypotheses.
• Laws and theories are the products of science.
• Evolution is the unifying theory of modern
  biology.