Characteristics of Living Things

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Characteristics of Living Things
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Defining a living thing is a difficult task.

• How would you define living?
• What is life?
• What do you need to survive?
• What does a plant need?
• What does a fish need?

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A living thing possesses certain properties that
help define what life is.
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1. Cells
Amoeba - single celled organism
Snail - multi-celled organism

• All living things are made up of one or more
  cells.
• The cell is the smallest functioning unit of all
  living things.
• A living thing can be composed of one cell or
  many cells.

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Cells

• Cells are usually too small to be seen with the
  naked eye.
• Cells are organized into tissues - a group of
  cells that perform the same function.
• Tissues form organs such as the stomach and
  kidney.
• A number of organs compose an organ system such
  as the digestive system.
• An organism is a complex structure of organ
  systems.

Human Heart
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2. Metabolism

• All living things are capable of taking materials
  from the surroundings and using them for energy
  to survive.
• Organisms acquire nutrition by absorption,
  photosynthesis or ingestion.

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3. Response to Stimuli

• All living things are able to respond to stimuli
  in the environment.
• Living things respond to light, heat, sound and
  contact with chemicals or other objects.
• Organisms can detect stimuli with eyes, ears,
  taste buds etc.

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4. Growth

• All organisms grow or mature over time.
• During growth a living thing transforms material
  that is unlike itself into materials that are
  like it.
• A human digests a meal of meat and vegetables and
  transforms the material into more of him/herself.

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5. Reproduction

• All living things contain the universal genetic
  code and have the ability to produce copies of
  itself by a process called reproduction.
• Bacteria grow quickly and split into two
  organisms by a process called asexual
  reproduction.
• More complex organisms, like animals, engage in
  sexual reproduction which requires two parents
  that contribute genes to their offspring.

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6. Respiration

• All living things exchange gas with the
  environment.
• Animals inhale oxygen gas and exhale carbon
  dioxide gas
• Plants absorb carbon dioxide from the environment
  and release oxygen.
• Organisms perform chemical reactions during
  respiration.

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7. Homeostasis

• All living things must maintain a stable internal
  condition no matter the environment.
• Animals regulate body temperature by sweating or
  shivering.
• Organisms perform chemical reactions and have
  physical properties that help to maintain
  homeostasis.

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8. Evolution

• Populations of organisms have the ability to
  adapt to their environment through the process
  called evolution.
• During evolution changes occur in populations,
  and the organisms in the population become better
  able to metabolize, respond and reproduce.
• Organisms develop abilities to cope with their
  environment that their ancestors did not.