Biology- The study of life, the diverse forms of life found on Earth.
• In order to make discoveries, biologists must view life from many different
1.1 The Principles of Life and Levels of Biological Organization
The Unifying Principles That Guide Our Understanding of Life
Principal 1: Cells are the Simplest Units of Life
• Organisms maintain an internal order that is separated from the environment.
• The simplest unit of an organism is the cell.
• The cell theory: 1) All organisms are composed of cells. 2) Cells are the
smallest units of life. 3) New cells come from pre existing cells via cell
• Unicellular organisms- composed of one cell
• Multicellular organisms- (plants, animals) composed of many cells
Principal 2: Living Organisms use Energy
• The maintenance of organization requires energy
• All living organisms acquire energy from the environment and use that energy
to to maintain their internal order.
• Cells carry out many internal chemical reactions that are responsible for
breaking down nutrients
• Respiration is one of these processes
• The energy can be used to synthesize the components that make up individual
cells and living organisms.
• chemical reactions involved with the breakdown and synthesis of cellular
molecules are collectively known as metabolism.
• plants can harness energy through photosynthesis
• Animals and fungi are consumers, they must use other organisms as food to
• some bacteria can use inorganic compounds such as sulphur, iron or
ammonium as sources of energy
Principal 3: Living Organisms Interact with Their Environment
• Organisms must be able to respond and adapt to environmental changes
• In the winter, many mammals develop thicker coats to protect them from the
• Plants change their angle towards the sunlight
Principal 4: Living Organisms Have Mechanisms That Maintain
• Living organisms regulate their cells and bodies to maintain relatively stable
• Mammals and birds tend to keep the same body temperature, even if they are
in a different environment
• all organisms continually regulate their cellular metabolism so that nutrient molecules are used at an appropriate rate and new cellular components
are synthesized when needed
Principal 5: Living Organisms Grow, Develop and Reproduce
• Growth produces more or larger cells.
• Multicellular organisms begin as one cell, and then undergo multiple cell
divisions to develop into a complete organism with many cells
• In order to sustain life, organisms must reproduce to generate offspring
• Unicellular organisms increase in volume by the synthesis of cellular
Principle 6: The Genetic Material, DNA, Provides a Dynamic Plan For
• offspring tend to have characteristics that greatly resemble their parents.
• All living organisms contain genetic material composed of DNA, which provides
a dynamic plan for their organization, development and function.
• During reproduction a copy of the DNA is transmitted from parent to offspring.
Principal 7: Populations of Organisms Evolve from One Generation to the
• Evolution is a biological characteristic of life.
• It refers to heritable change in the DNA of a population of organisms from
generation to generation.
• This can be detectable differences that help the population become better
adapted to the environment in which they live.
Principal 8: All Life is Related by an Evolutionary History
• Evolution is an ongoing process that happens from one generation to the next.
• DNA samples from fossils suggest that all organisms on earth share a common
Principal 9: Organisms Follow the Laws of Chemistry and Physics, and
Structure Determines Function
• Living organisms follow the laws of chemistry and physics
• "structure determines function"
• size, shape etc. determines function.
Living Organisms Can Be Viewed And Studied At Different Levels of
Atoms- The smallest component of an element that gas the chemical properties
of that element. All matter is composed of atoms
Molecules and Macromolecules- Atoms bond with each other to form
molecules. When many similarly structured molecules bond together to form a
polymer, a macromolecule is the result. (Ex. Carbohydrates, proteins, nucleic
Cells- Molecules and macromolecules associate with one another to form
organized larger structures (organelles) that are enclosed in a cell membrane
Tissues- Many cells of the same typee associate with each other to form tissues. EX. muscle tissue
Organs- an organ contains two or more types of tissues. EX. the heart
compromises of many different tissues including muscle, nervous and
Organ Systems- Organs can work together as an organ system to accomplish a
larger function for the organs. EX. cardiovascular system- heart, blood vessels
Organism- Some are single celled, some consist of billions of cells organized
into organs and organ systems.
Species- Species are a group of organisms that share