Chapter 1 The Science of Biology

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Chapter 1 The Science of Biology
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11 What Is Science?

• Science is a process of inquiry, asking
  questions, the answers to which produce a body of
  knowledge, which is subject to change and
  revision.
• The goal of science is to investigate and
  understand the natural world, to explain events
  in the natural world and to use those
  explanations to make useful predictions.

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• Science only deals with the natural world.
  Biology is a field in science that focuses on the
  study of life.
• An understanding of science and the scientific
  approach is essential to making intelligent
  decisions.

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• Scientists collect and organize information in a
  careful, orderly way, looking for patterns and
  connections between events.
• Scientists propose explanations that can be
  tested by examining evidence. Scientists try to
  explain events logically and analytically.

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• Scientific thinking begins with observation, the
  process of gathering information about events or
  processes in a careful, orderly way.
• Observation generally involves using the senses,
  particularly sight and hearing. The information
  gathered from observations is called data. Data
  consists of observations that do not differ
  whether collected by one person or another.

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• Two types of data
• Quantitative data expressed in numbers, obtained
  by counting or measuring.
• Qualitative data descriptive and involves
  characteristics that cant usually be counted.

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• Scientists use data to make inferences, a logical
  interpretation based on prior knowledge or
  experience.
• After initial observations, a hypothesis is
  proposed. A hypothesis is a proposed scientific
  explanation for a set of observations.
• Scientific hypotheses must be proposed in a way
  that enables them to be tested.

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• Science is an ongoing process, knowledge is
  constantly being reevaluated, revised and updated
  because of new tools, techniques and discoveries.
• Good scientists are skeptics, questioning
  existing ideas and new hypotheses.
• Common steps for scientists to gather information
  and answer questions are known as scientific
  methods. Not every scientific investigation uses
  every method nor do all investigations lead to
  scientific theory.

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1-2 How Scientists Work

• While there are no fixed steps, generally the
  scientific method involves
• MAKE OBSERVATIONS observations utilize the
  senses to gather information. Scientific
  discovery often takes place when a scientist
  observes something no one has noticed before.

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• ASK A QUESTION observations may lead to
  unanswered questions. (Research may provide
  information about previous investigations of the
  question or suggest appropriate approaches to the
  problem.)
• FORM A HYPOTHESIS an explanation for a question
  or a problem that can be formally tested. A good
  hypothesis predicts a relationship between cause
  and effect.

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• SET UP A CONTROLLED EXPERIMENT While we use the
  term experiment informally, a scientific
  experiment is an investigation that tests a
  hypothesis by the process of collecting
  information under controlled conditions. A
  controlled experiment involves two groups

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• Variable (Experimental) group test group that
  receives experimental treatment. A variable is
  the factor of an experiment that can change. In
  a controlled experiment, only one variable is
  tested at a time. There are three types of
  variables
• Controlled (constant) variables same for both
  the control and variable group.
• Manipulated (independent) variable variable that
  is deliberately changed.
• Responding (dependent) variable changes in
  response to the manipulated variable (what
  happened).

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• Control group group that receives no
  experimental treatment, the standard against
  which results are compared.

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• RECORD AND ANALYZE RESULTS keeping a written
  record of observations and data. Data from an
  investigation can be considered confirmed only if
  repeating the investigation several times yields
  similar results.
• DRAWING A CONCLUSION Use evidence to determine
  whether the hypothesis was supported or refuted.

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• REPORTING RESULTS Results are only useful if
  they are made available to other scientists for
  peer review. Other scientists can try to verify
  the results by repeating the procedure.

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• It is not always possible to do an experiment to
  test a hypothesis.
• Alternative investigations may utilize fieldwork
  or surveys or large groups of subjects,
  controlling as many variables as possible.
• As evidence accumulates from scientific
  investigations, a particular hypothesis may
  become so well supported that scientists consider
  it a theory. A theory is a well-tested
  explanation that unifies a broad range of
  observations.
• No theory is considered absolute truth. As new
  evidence is uncovered, a theory may be revised or
  replaced.

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1 3  Studying Life

• The word biology means the study of life. A
  biologist is someone who uses scientific methods
  to study living things.
• Describing what makes something alive is not
  easy.
• No single characteristic is enough to describe a
  living thing.
• Some non-living things share one or more traits
  with living things.

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Living things share the following characteristics
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1. Living things are made up of units called
cells.
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• All living things show an orderly structure,
  known as organization.
• Although living things are very diverse, they are
  all unified in having cellular organization.
• A cell is a collection of living matter enclosed
  by a barrier (cell membrane) that separates the
  cell from its surroundings.
• The cell is the lowest level of structure capable
  of performing all of the activities of life.
• Cells are complex and highly organized despite
  their small size.
• Unicellular organisms are living things that
  consist of only a single cell.
• Multicellular organisms contain hundreds,
  thousands or even trillions of cells with a
  variety of shapes and sizes. Each type of cell
  is specialized to perform a different function.

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2. Living things reproduce.
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• All organisms produce new organisms (offspring)
  through a process called reproduction.
• Reproduction is essential for the continuation of
  an organisms species (group of organisms that
  can interbreed and produce fertile offspring in
  nature.)
• There are two types of reproduction
• Sexual reproduction two cells from different
  parents unite to produce the first cell of the
  new organism. Offspring differ from their
  parents in some ways.
• Asexual reproduction new organism has a single
  parent. Offspring and parents have the same
  traits.

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3. Living things are based on a universal genetic
code.
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• The directions for inheritance are carried by a
  molecule called deoxyribonucleic acid (DNA).
• Every organism, with a few minor variations,
  interprets the genetic code of DNA in the same
  way.

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4. Living things grow and develop.
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• Growth is an increase in the amount of living
  material and the formation of new structures.
• Growth can occur by increasing the size of a
  single cell or increasing the number of cells.
• Development is all of the changes that take place
  during the life of an organism.
• The development of specialized cells from a
  single fertilized egg cell is called
  differentiation, because the cells produced look
  different and perform different functions.

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5. Living things obtain and use materials and
energy.
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• Organisms take in energy and transform it to do
  many kinds of work.
• Organisms use a constant supply of materials and
  energy to grow, develop, reproduce, and stay
  alive.
• The combination of chemical reactions through
  which an organism builds up or breaks down
  materials as it carries out life processes is
  called metabolism.
• All organisms get the material they need from
  their surroundings, or environment. The way
  organisms obtain energy varies.
• Plants, some bacteria and most algae obtain their
  energy directly from sunlight through
  photosynthesis. They convert light into a form
  of stored energy in molecules ready to be used
  when needed.
• Other organisms rely on photosynthetic organisms
  for their energy by eating plants or indirectly
  by eating organisms that ate plants. Decomposers
  obtain energy from organisms that have died.

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6. Living things respond to their environment.
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• Organisms live in a constant interface with their
  surroundings, or environment, which includes
  other living organisms (biotic factors) as well
  as non-living factors (abiotic factors) like air,
  water, temperature and weather.
• Anything in an organisms external or internal
  environment that causes to react is a stimulus.
  A reaction to a stimulus is a response.
• External stimuli, which come from the environment
  outside an organism, include light and
  temperature.
• Internal stimuli come from within an organism.
  For example, trees that drop their leaves in the
  fall conserve water and avoid freezing during the
  winter.

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7. Living things maintain a stable internal
environment.
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• Even though conditions in the external
  environment may vary widely, the internal
  conditions of most organisms stay fairly
  constant.
• The process by which they do this is called
  homeostasis.
• A breakdown in homeostasis can result in disease
  or even death.
• Homeostasis often involves internal feedback
  mechanisms, which respond to internal stimuli. A
  thermostat in your home maintains a constant
  temperature in your home.

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Negative feedback mechanismA thermostat
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• A similar thermostat regulates human body
  temperature.
• Human body temperature is a constant 37oC
  (98.6oF), regardless of the external temperature
  of the environment.
• If the external temperature gets too hot and
  causes the human body temperature to rise, the
  body responds by sweating, which helps remove
  excess heat from the skin.
• If the external temperature gets too cold and
  causes the human body temperature to drop, the
  body responds by shivering.
• The muscle contraction when shivering produces
  heat, warming the body.

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• Another example of homeostasis human blood
  sugar levels.
• The blood contains a constant amount of sugar in
  the blood. Yet the amount of sugar available to
  the body changes.
• After you eat a meal high in sugar, blood sugar
  levels rise.
• This stimulates the pancreas to produce a hormone
  (chemical signal) called insulin.
• Insulin targets the liver and muscle cells of the
  body and tells them to take up the excess sugar
  and store it, bringing blood sugar levels back to
  normal.
• After several hours of not eating, the sugar in
  the blood is used by the cells for energy,
  causing the blood sugar levels to drop.
• This stimulates the production of a second
  hormone from the pancreas called glucagon.
• Glucagon stimulates the liver and muscles to
  release sugar into the blood and help raise the
  blood sugar levels back to normal.

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• Animals are not the only organisms to use
  homeostasis.
• Plants must regulate carbon dioxide intake and
  water loss.
• Plants use structures call stomata (singular
  stoma) to do so.
• Stomata are microscopic holes in a plant leaf
  (usually on the underside) that allow gases to
  enter and leave and water vapor to leave as well.
  
• Each stoma consists of two guard cells, which
  control the opening and closing of stomata by
  responding to changes in water pressure.
• When guard cells are swollen with water, the
  stoma is open.
• When the guard cell loses water, the opening
  closes, limiting further water loss from the leaf.

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Plant Leaf
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8. Taken as a group, living things change over
time.
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• Although individual organisms experience many
  changes during their lives, the basic traits they
  inherited from their parents usually do not
  change.
• A group of organisms, however, can change over
  time through the process of evolution.
• Any inherited structure, behavior or internal
  process that enables an organism to respond to
  environmental factors and live to produce
  offspring is called an adaptation.

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• There are always some differences in the
  adaptations of individuals within any population
  of organisms.
• As the environment changes, some individuals have
  adaptations that make them better suited to the
  new conditions and more likely to survive and
  reproduce. As a result, individuals with these
  adaptations become more numerous in the
  population.
• Over time, the characteristics of a species will
  change so that all individuals have the
  adaptation.
• This process of change over time is called
  evolution. Life evolves as a result of the
  interaction between organisms and their
  environments.