Levels of Organization of Living Things

Levels of Organization of Living Things

• Living things are organized in a hierarchy from smallest to largest: chemical, cellular, tissue, organ, organ system, and organism.
• Chemicals are the most fundamental unit.
• The smallest unit of matter is the atom.
• Atoms bond to form molecules.
• Molecules combine to form larger complex structures called macromolecules.
• Examples of macromolecules include DNA, which has instructions for all living organisms.

Molecules and Macromolecules

• A molecule is a chemical structure consisting of two or more atoms held together by chemical bonds.
• Many molecules are biologically important macromolecules.
• Macromolecules are typically formed by polymerization.
• Polymerization involves combining smaller units (monomers) to create larger molecules.
• Deoxyribonucleic acid (DNA) is an example of a macromolecule.

Cells and Organelles

• Cells are the basic structural and functional units of living organisms.
• Some cells contain organelles, which are small structures within cells.
• Organelles have specific functions, such as producing energy (mitochondria) or making sugars (chloroplasts).
• Cells are the smallest units that exhibit all characteristics of life.

Tissues, Organs, and Organ Systems

• Tissues are groups of similar cells that perform a specific function.
• Organs are collections of tissues that work together to perform a complex function.
• Organ systems are groups of organs working together to perform an even broader set of tasks necessary for the organism.

Organism

• Organisms are individual living entities.
• Single-celled organisms or multicellular organisms.

Populations

• A population includes all the members of a species living in a defined area.

Communities

• A community consists of all the populations of different species living and interacting within a particular area..

Ecosystems

• An ecosystem includes all the living organisms (biotic factors) in a particular area and the non-living environment (abiotic factors) .

Biosphere

• The biosphere is the highest level of organization.
• The biosphere includes all ecosystems on Earth.